Academic literature on the topic 'Alkene hydrogenation'

Bio-diesel was synthesized by hydrogenating the non-polar fraction of the bio-oil produced from the co-pyrolysis between corncobs and polypropylene. Co-pyrolysis of corn cobs and polypropylene was conducted in a stirred tank reactor at heating rate of 5°C/min and maximum temperature of 500°C to attain synergetic effect in non-polar fraction yield where polypropylene served as a hydrogen donor and oxygen sequester so that the oxygenate content in the biofuel product reduced. Stirred tank reactor configuration allowed phase separation between non-polar and polar (oxygenate) compounds in the bio-oil. Hydrogenation reaction of the separated non-polar phase, which contained alkenes, was carried out in a pressured stirred tank reactor using a NiMo/C catalyst in order to reduce the alkene content in the bio-oil. The aim of the present work is to reduce the alkene content in the separated non-polar fraction of bio-oil by catalytic hydrogenation to obtain biofuel with low alkene content and viscosity approaching to that of diesel fuel. To quantify effect of the pressure on the alkene composition, the experiment was done at H2 initial pressures of 4, 7, 10, and 13 bar and at corresponding saturation temperatures of octane. The biofuel products were characterized using GC-MS, LC-MS, FTIR spectroscopy, H-NMR, Higher heating values (HHV) and viscometer for comparison with those of commercial diesel fuel. Analysis of the lower molecular weight fractions of biofuels by GC-MS found that the hydrogenation reactor at pressures at 4 and 7 bar produced biofuels with predominant hydrocarbon contents of cycloalkanes and alkanes, while that at 10 and 13 bar produced biofuels with predominant contents of alkanes and alkenes. In comparison, diesel fuel contains mostly alkanes and aromatics. However, analysis over the whole content of bio-oil by H-NMR found that different pressures of reactor hydrogenation did not reduce alkene compositions in biofuels appreciably from alkene composition in bio-oil feed. In comparison, diesel fuel contained mostly alkanes with aromatic composition about 4% and no alkene content. Various data suggest that alkene content in the biofuels be reduced to approach their viscosity to that of diesel fuel. Modification of the hydrogenation reactor is required by improving convective momentum of hydrogen gas into the bio-oil to enhance contact of solid catalyst, hydrogen gas and bio-oil.

A series of low-loaded metallic-activated carbon catalysts were evaluated during the selective hydrogenation of a medium-chain alkyne under mild conditions. The catalysts and support were characterized by ICP, hydrogen chemisorption, Raman spectroscopy, temperature-programmed desorption (TPD), temperature-programmed reduction (TPR), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR micro-ATR), transmission electronic microscopy (TEM), and X-ray photoelectronic spectroscopy (XPS). When studying the effect of the metallic phase, the catalysts were active and selective to the alkene synthesis. NiCl/C was the most active and selective catalytic system. Besides, when the precursor salt was evaluated, PdN/C was more active and selective than PdCl/C. Meanwhile, alkyne is present in the reaction media, and geometrical and electronic effects favor alkene desorption and so avoid their overhydrogenation to the alkane. Under mild conditions, nickel catalysts are considerably more active and selective than the Lindlar catalyst.

Scandium and yttrium congeneric complexes, supported by a monoanionic PNP ligand, were studied as catalysts for alkene hydrogenation and hydrosilation and alkyne semihydrogenation and semihydrosilation.

Competitive hydrogenation of alkenes (cyclohexene, hex-1-ene, hept-1-ene, oct-1-ene) and dienes (octa-1,7-diene, cyclohexa-1,3-diene) was carried out by catalytic hydrogen transfer from ammonium formate on palladium in methanol. The adsorptivity and reactivity of the hydrocarbons decreased in the series: cyclic diene > linear diene > linear 1-alkene > cyclic alkene.

The combination of intermolecular enyne cross metathesis and subsequent 1,4-hydrogenation opens a stereocontrolled and atom-economic access to trisubstituted olefins. By investigating different combinations of functionalized alkyne and alkene substrates, we found that the outcome (yield, E/Z ratio) of the Grubbs II-catalyzed enyne cross-metathesis step depends on the substrate’s structure, the amount of the alkene (used in excess), and the (optional) presence of ethylene. In any case, the 1,4-hydrogenation, catalyzed by 1,2-di­methoxybenzene-Cr(CO)3, proceeds stereospecifically to yield exclusively the E-products from both the E- and Z-1,3-diene intermediates obtained by metathesis. A rather broad scope and functional group compatibility of the method is demonstrated by means of 15 examples.

It is shown that the reduction of alkenes by hydrogen atom transfer provides selectivities that are distinct from classical hydrogenation catalysts. The first alkene hydrobromination, hydroiodination, and hydroselenylation reactions that proceed by hydrogen atom transfer processes are also reported.

Rhodium(i) alkene complexes of an NNN-pincer ligand catalyze the hydrogenation of alkenes. The terminal or resting state of the catalyst, which exhibits an unusually upfield Rh–hydride ¹H NMR chemical shift, has been identified.

The work described in this thesis explores the influence of the nature of transition metals, the electronic properties of ligands and the effect of counter-ions in the regioselectivity of transition metal-hydride addition (hydrometalation) to carbon-carbon double bonds. The method used to investigate the regioselectivity of the hydrometalation was based on the established methodology [Mode a (M^δ+ - H^δ-) and Mode b (M^δ- - H^δ+)]. The cis-alkenes were subjected to hydrogenation using deuterium gas. Following the hydrometalation step, the rotation of one end of the substrate would give a trans-conformation, which would transform to the trans-isomer via β-hydride elimination. The location of the deuterium on the double bond would indicate the regioselectivity of the hydrometalation. Chapter 2 investigates the intrinsic nature of transition metal-hydrides, namely Pd/C, Pt/C and Rh/C. The behaviour of each M-H addition to the double bond of alkenes is compared, in an attempt to reveal the periodic trend in the transition metals. Information on the nature of these catalysts would be useful for modification of the catalysts in order to improve selectivity. Chapter 4 demonstrates the effect of the electronic properties of ligands in controlling the regioselectivity of hydrometallation. Wilkinson's catalyst is taken as a model system. A range of ligands bearing different electron-withdrawing and electron-donating substituents are synthesized and are then used to make Wilkinson's type catalysts. These catalysts are used in the hydrogenation of cis-β-methoxystyrene using deuterium gas. The implication of the findings for chiral induction is discussed. Chapter 5 describes an extension of the methodology to another class of catalyst, Ir-phosphinooxazolines. These complexes have been shown to be efficient catalysts for the asymmetric hydrogenation of alkenes. The effect of the counter-ions of the complexes on the regioselectivity of the hydrometalation is investigated.

The work reported in this thesis is concerned with two separated but related studies. The first involved examination of hydrogenation reactions of alkenes, dienes and alkynes using (Rh[sub]2C1(CO)[sub]2(dppm)[sub]2JBPh[sub]4 as a catalyst. Kinetic studies have been performed on the reaction of hexene. The system only well-behaved in the presence of a base, R[sub]3N, where a rst order dependance on both catalyst and hydrogen concentations observed. The order with respect to alkene is of the Michaelis-Menton type. This behaviour suggests that the active catalyst is a neutral monohydride generated by deprotonation of a ionic dihydride. It is proposed that the active catalyst is a dinuclear species, since none of the likely mononuclear breakdown oducts shows any catalytic activity. A catalytic cycle for the reaction is proposed. The second study was an investigation into the use of fast atom bombardment (FAB) mass spectrometry as a means of anaylsis organometallic compounds which have proved difficult to identify using other ionisation modes. The technique was shown to informative spectra for a series of dinuclear rhodium-dppm mplexes and some dinuclear manganese carbonyl derivatives. FAB ionisation also proved effective for identification of phosphine and phosphite derivatives of [RCC0[sub]3(CO)[sub]9.] (R=CH[sub]3, C1). The technique was also combined with thin layer chromatography (TLC) in examining a reaction of [Mo(CO)[sub]6.] with Ph[sub]2P(CH[sub]2)[sub]2P(O)Ph[sub]2 (dppeO) which yields a mixture of seven products. It was found that good spectra of pure materials could be obtained TLC separation, followed by removal of the appropriate section silica support from the plate. This was subjected directly to FAB mass spectrometry without prior extraction of the product from silica. Using this technique, it proved possible to identify three new dppeO derivatives of [Mo(CO)[sub]4 (dppeO) derivatives of [Mo(CO)[sub]6. These are [Mo(CO)[sub]5 (dppeO)] cis-[Mo(CO)[sub]4 (dppeO)[sub]2] and [Mo[sub]2(CO)[sub] 4 (dppeO)[sub]2].

Thesis (PhD)--Stellenbosch University, 2015.
ENGLISH ABSTRACT: The synthesis of a range of siloxane functionalized Ru(arene)Cl(N,N) complexes allowing for the synthesis of novel MCM-41 and SBA-15 immobilized ruthenium(II) catalysts, is described in this thesis. Two distinctly different approaches were envisaged to achieve successful heterogenization of these siloxane functionalized complexes. Condensation of the siloxane functionalized complexes, C2.4-C2.6 (siloxane tether attached to imine nitrogen) and C3.5-C3.7 (siloxane tether via the arene ring), with the surface silanols of the synthesized silica support materials MCM-41 and SBA-15, afforded immobilized catalysts IC4.1-IC4.6 (siloxane tether attached to imine nitrogen) and IC4.7-IC4.12 (siloxane tether via the arene ring). Model and siloxane functionalized complexes C2.1-C2.6 were prepared by the reaction of diimine Schiff base ligands L2.1-L2.6 with the [Ru(p-cymene)2Cl2]2 dimer. A second, novel, approach involved the introduction of the siloxane tether on the arene ligand of the complex. Cationic arene functionalized Ru(arene)Cl(N,N) complexes, C3.1-C3.4, were prepared with varying N,N ligands including bipyridine and a range of diimine ligands, with either propyl or diisopropyl(phenyl) substituents at the imine nitrogen (greater steric bulk around the metal center). The reaction of these propanol functionalized complexes with 3-(triethoxysilyl)propyl isocyanate, afforded urethane linked siloxane functionalized complexes C3.5-C3.8, where the siloxane tether is attached to the arene ring of the complex. The complexes were fully characterized by FT-IR spectroscopy, NMR (1H and 13C) spectroscopy, ESI-MS analysis and microanalysis. Suitable crystals for the alcohol functionalized complex C3.1 were obtained and the resultant orange crystals were analyzed by single crystal XRD. The heterogenized catalysts, IC4.1-IC4.12, were characterized by smallangle powder X-ray diffraction, scanning and transmission electron microscopy (SEM and TEM), thermal gravimetric analysis (TGA), inductively coupled plasma optical emission spectroscopy (ICP-OES) and nitrogen adsorption/desorption (BET) surface analysis to name but a few. ICP-OES allowed for direct comparison of the model and immobilized systems during catalysis ensuring that the ruthenium loadings were kept constant. The application of the model complexes C2.1-C2.3 and C3.1-C3.3, as well as their immobilized counterparts, IC4.1-IC4.12, as catalyst precursors in the oxidative cleavage of alkenes (1-octene and styrene), were investigated. The proposed active species for the cleavage reactions was confirmed to be RuO4 (UV-Vis spectroscopy). In general it was observed that at lower conversions, aldehyde was formed as the major product. Increased reaction times resulted in the conversion of the formed aldehyde to the corresponding carboxylic acid. For the oxidative cleavage of 1-octene using the systems with the siloxane tether attached to the imine nitrogen, the immobilized systems outperformed the model systems in all regards. Higher conversions and selectivities of 1-octene towards heptaldehyde were obtained when using immobilized catalysts IC4.1-IC4.6, as compared to their non-immobilized model counterparts (C2.1-C2.3) at similar times. It was found that the immobilized catalysts could be used at ruthenium loadings as low as 0.05 mol %, compared to the model systems where 0.5 mol % ruthenium was required to give favorable results. Complete conversion of 1-octene could be achieved at almost half the time needed when using the model systems as catalyst precursors. The activity of the model systems seems to increase with the increase in steric bulk around the metal center. These model and immobilized systems were also found to cleave styrene affording benzaldehyde in almost quantitative yield in some case (shorter reaction times). The systems, with the siloxane tether via the arene ring, were found to be less active for the cleavage of 1-octene when compared to the above mentioned systems (siloxane tether attached to the imine nitrogen). The immobilized systems IC4.7-IC4.12 performed well compared to their model counterparts, but could not achieve the same conversions at the shorter reaction times as were the case for IC4.1-IC4.6. This lower activity was ascribed to the decreased stability of these systems in solution compared to the above mentioned systems with the tether attached to the imine nitrogen. This was confirmed by monitoring the conversion of the complex (catalyst precursor) to the active species in the absence of substrate (monitored by UV-Vis spectroscopy). It was observed that model complex C3.1 could not be detected in solution after 1 hour, compared to complex C2.2 which was detected in solution even after 24 hours. Experiments were carried out where MCM-41 was added to a solution of model complex C2.2 under typical cleavage reaction conditions. A dramatic increase in the conversion was achieved when compared to a reaction in the absence of MCM-41. An investigation into the effect of the support material on the formation of the expected active species was carried out using UV-Vis spectroscopy. The presence of the active species, RuO4, could be observed at shorter reaction times in the presence of MCM-41. This suggested that the silica support facilitates the formation of the active species from the complex during the reaction, therefore resulting in an increased activity. It was also observed that RuO4 is present in solution in reactions where the immobilized catalyst systems are used after very short reaction times, compared to the prolonged times required for this to occur as is the case for the model systems. Model and immobilized catalysts, C2.1-C2.3 and IC4.1-IC4.6, were also applied as catalysts for the transfer hydrogenation of various ketones. The immobilized systems could be recovered and reused for three consecutive runs before the catalysts became inactive (transfer hydrogenation of acetophenone). Moderate to good conversion were obtained using the immobilized systems, but were found to be less active their model counterparts C2.1-C2.3.
AFRIKAANSE OPSOMMING: Die sintese van `n reeks siloksaan gefunksioneerde Ru(areen)Cl(N,N) komplekse, wat die sintese van nuwe MCM-41 en SBA-15 geimmobiliseerede rutenium(II) katalisatore toelaat, word in hierdie tesis beskryf. Twee ooglopend verskillende metodes is voorgestel om die suksesvolle immobilisering van die siloksaan gefunksioneerde komplekse te bereik. Die kondensasie van die siloksaan gefunksioneerde komplekse, C2.4-C2.6 (siloksaan ketting geheg aan die imien stikstof) en C3.5-C3.7 (siloksaan ketting geheg aan die areen ligand), met die oppervlak silanol groepe van die silika materiale MCM-41 en SBA-15, laat die sintese van geimmobiliseerde katalisatore IC4.1-IC4.6 (siloksaan ketting geheg aan die imien stikstof) en IC4.7-IC4.12 (siloksaan ketting geheg aan die areen ligand) toe. Model en siloksaan gefunksioneerde komplekse C2.6-C2.6 is berei deur die reaksie tussen Schiff basis ligande, L2.1-L2.6, en die [Ru(p-simeen)2Cl2]2 dimeer. `n Tweede, nuwe benadering wat die sintese van komplekse met die siloksaan ketting geheg aan die areen ligand behels, is ook gevolg. Kationiese areen gefunksioneerde Ru(areen)Cl(N,N) komplekse, C3.1-C3.4, is berei deur die N,N ligande rondom die metaal sentrum te wissel vanaf bipiridien tot `n reeks diimien ligande met propiel of diisopropielfeniel substituente by die imien stikstof. Hierdie propanol gefunksioneerde komplekse is met 3-(triëtoksiesiliel)propiel-isosianaat gereageer om sodoende die uretaan gekoppelde siloksaan gefunksioneerde komplekse C3.5-C3.8 op te lewer. Al die komplekse is ten volle gekaraktariseer deur van FT-IR spektroskopie, KMR (1H and 13C) spektroskopie, ESI-MS analise en mikroanalise gebruik te maak. In die geval van model kompleks C3.1, is `n kristalstruktuurbepaling ook uitgevoer. Die heterogene katalisatore, IC4.1- IC4.12, is gekaraktariseer deur poeier X-straaldiffraksie, skandeer- en transmissieelektronmikroskopie, termogravimetriese analise (TGA), induktief gekoppelde plasma optiese emissie spektroskopie (IKP-OES) en BET oppervlak analises, om net `n paar te noem. IKP-OES het ons toegelaat om `n direkte vergelyking te tref tussen die model en geimmobiliseerde sisteme tydens die katalise reaksies. Model komplekse C2.1-C2.3 en C3.1-C3.3, sowel as hul geimmobiliseerde eweknieë IC4.1- IC4.12, is vir die oksidatiewe splyting van alkene (1-okteen en stireen) getoets. Die voorgestelde aktiewe spesie wat tydens hierdie reaksie gevorm word, RuO4, is bevestig deur van UV-Vis spektroskopie gebruik te maak. Oor die algemeen is dit gevind dat aldehied oorheersend gevorm word by laer omsetting. Wanneer die reaksietyd verleng is, is daar gevind dat die aldehied na die ooreenstemmende karboksielsuur omgeskakel is. Wanneer die geimmobiliseerde katalisatore gebruik is tydens die oksidatiewe splitsing van 1-okteen, het die sisteme, met die ketting geheg aan die imien stikstof, deurgangs beter as die model sisteme gevaar. Hoër omskakelings van 1-okteen en hoë selektiwiteite vir heptaldehied is behaal wanneer die geimobiliseerded katalisatore IC4.1-IC4.6 met die nie-geimmobiliseerde model sisteme (C2.1- C2.3) vergelyk is by dieselfde reaksietye. Die geimobiliseerde sisteme kon by rutenium beladings van so laag as 0.05 mol % gebruik word. Dit is in teenstelling met die model sisteme waar 0.5 mol % rutenium nodig was om die reaksie suksesvol te laat plaasvind. Die totale omskakeling van 1-okteen is bereik in die helfte van die tyd wat nodig was wanneer die model sisteme gebruik is. Dit is gevind dat die aktiwiteit van die model sisteme toeneem met `n toename in die steriese grootte van die ligand rondom die metaal. Beide die model en geimmobilseerde sisteme kon ook gebruik word vir die oksidatiewe splyting van stireen. Bensaldehied kon in kwantitiewe opbrengs gevorm word in sommige gevalle. `n Laer aktiwiteit vir die oksidatiewe splyting van 1-okteen is vir die sisteme waar die siloksaan ketting aan die areen ligand geheg is, waargeneem. Hoewel die geimmobiliseerde sisteme IC4.7-IC4.12 beter as hul model eweknieë gevaar het, kon die aktiwiteite wat met IC4.1-IC4.6 bereik is nie geewenaar word nie. Hierdie laer aktiwiteit is toegeskryf aan die verlaagde stabiliteit van dié sisteme in oplossing in vergelyking met IC4.1-IC4.6 (ketting geheg aan die imine stikstof). Die stabiliteit van beide sisteme is getoets deur die omskakeling van die model komplekse (C2.2 en C3.1; katalise voorgangers) na die aktiewe spesie te monitor (UV-Vis spektroskopie). Na 1 uur kon die model kompleks C3.1 nie meer in die oplossing waargeneem word nie. In teenstelling kon model kompleks C2.2 nog selfs na 24 uur in die oplossing bespeur word. Om die rol van die silika materiale tydens die reaksie te ondersoek, is `n eksperiment uitgevoer waar MCM-41 by `n oplossing van kompleks C2.2 gevoeg is. `n Toename in die omskakeling van 1-okteen is waargeneem in vergelyking met `n reaksie waar geen silika teenwoordig was nie. UV-Vis spektroskopie is gebruik om die invloed van die silika op die vorming van die aktiewe spesie te ondersoek. In eksperimente waar MCM-41 teenwoordig was, kon die aktiewe spesie, RuO4, by baie korter reaksietye waargeneem word. Dit wil blyk of die silika materiaal die vorming van die aktiewe spesie vanaf die kompleks aanhelp en sodoende `n toename in die spoed van die reaksie bewerkstellig. RuO4 kon ook by baie korter reaksietye waargeneem word wanneer die geimmobiliseerde sisteme gebruik is. Beide model en geimmobiliseerde sisteme, C2.1-C2.3 en IC4.1-IC4.6, is getoets vir die oordrag hidrogenering van verskilende ketone. Dit was moontlik om die geimmobiliseerde sisteme drie keer te herwin en vir daaropvolgende reaksies te gebruik. Vir die geimmobiliseerde sisteme kon egter slegs gemiddelde omskakelings verkryg word en het swakker gevaar as hul model ekwivalente sisteme, C2.1-C2.3.

Obtention de particules submicroniques (3 a 4nm) par reduction en milieu thf d'un halogenure de ni ou de pd par etmgbr. Etude de l'activite catalytique lors de l'hydrogenation en phase liquide de l'hexene-1, du cyclohexene, de l'hexyne-1 et -3 et du benzene

Ana C. Fernandes of the Instituto Superior Técnico, Lisboa, devised (Tetrahedron Lett. 2010, 51, 1048) an effective Re catalyst for the solvent-free hydrogenation of an alkene 1. Yasushi Imada and Takeshi Naota of Osaka University showed (Organic Lett. 2010, 12, 32) that a flavin could catalyze the hydrogenation of an alkene 3. Note that the thioether was stable under these conditions. Huanfeng Jian of the South China University of Technology developed (J. Org. Chem. 2010, 75, 2321) a Pd-based protocol for the oxidative cleavage of an alkene 5. The cleavage could be halted at the cis diol. K. C. Nicolaou of Scripps/La Jolla optimized (Organic Lett. 2010, 12, 1552) a complemetary cleavage of an alkene 7, again proceeding via the diol. J. R. Falck of UT Southwestern established (J. Org. Chem. 2010, 75, 1701) the Heck-type oxidative silylation of an alkene 9 to the Z -silane 10. Timothy F. Jamison of MIT effected (Chem. Commun. 2010, 46, 907) the borylation of an alkene 11. Kálmán Szabó of Stockholm University reported (Angew. Chem. Int. Ed. 2010, 49, 4051) a complementary approach for effecting the same transformation. Cathleen M. Crudden of Queen’s University, Kingston, observed (J. Am. Chem. Soc. 2010, 132, 131) that Rh-catalyzed hydroboration of 13 delivered the borane 14. Tehshik P. Yoon of the University of Wisconsin used (J. Am. Chem. Soc. 2010, 132, 4570) Fe to catalyze the addition of an oxaziridine 16 to an alkene 15. Yasuhiro Shiraishi of Osaka University improved (J. Org. Chem. 2010, 75, 1450) the photochemical addition of acetone to an alkene 18. Chul-Ho Jun of Yonsei University described (Tetrahedron Lett. 2010, 51, 160) a related procedure. Professor Jamison effected (J. Am. Chem. Soc. 2010, 132, 6880) the branching homologation of an alkene to give 21 . F. Dean Toste of the University of California, Berkeley, accomplished (J. Am. Chem. Soc. 2010, 132, 8885) the oxidative homologation of an alkene to the ester 22. Markus R. Heinrich of the Universität Erlangen-Nürnberg developed (Tetrahedron Lett. 2010, 51, 1758) the tandem addition of the hydroperoxide 23 and a diazonium salt 24, leading to 25.

Akio Baba of Osaka University combined (Chem. Lett. 2013, 42, 1551) reduction of the acid 1 with subsequent condensation with the ketene silyl acetal 2 to directly give the coupled product 3. Song-Lin Zhang of Soochow University showed (Chem. Commun. 2013, 49, 10635) that the allyl Sm reagent 5 could be added to an aldehyde 4 under reducing conditions, leading to the alkene 6. In a related development, Patrick Perlmutter of Monash University reduced (Org. Lett. 2013, 15, 4327) the interme­diate lactol from addition of the alkyl lithium reagent 8 to the lactone 7, to give the alcohol 9. Yoshihiro Miyake, now at Nagoya University, and Yoshiaki Nishibayashi of the University of Tokyo added (Chem. Commun. 2013, 49, 7854) the benzyl radical from the decarboxylation of 10 to the acceptor 11 to give 12. Yasuharu Yoshimi of the University of Fukui (Tetrahedron Lett. 2013, 54, 4324) and Larry E. Overman of the University of California, Irvine (J. Am. Chem. Soc. 2013, 135, 15342) reported related results. David Milstein of the Weizmann Institute of Science developed (Angew. Chem. Int. Ed. 2013, 52, 14131) an Fe catalyst for the hydrogenation of an alkyne 13 to the E-alkene 14. Zhi-Xiang Yu of Peking University showed (Org. Lett. 2013, 15, 4634) that kinetic isomerization of the alkene 15 led selectively to the Z-alkene 16. Umasish Jama of Jadavpur University prepared (Eur. J. Org. Chem. 2013, 4823) the nitroalkene 18 by condensing nitromethane with the aldehyde 17. Vladimir A. D’yakonov of the Russian Academy of Sciences, Ufa described (Chem. Commun. 2013, 49, 8401; Tetrahedron 2013, 69, 8516) the remarkably selective coupling of the allene 19 with the allene 20 to give the Z,Z-diene 21. Sang-Hyeup Lee of the Catholic University of Daegu assembled (Synlett 2013, 24, 1953) the ketone 24 by coupling the alkynyl aluminum 23 with the nitrile 22. Jean-Marc Weibel and Patrick Pale of the Université de Strasbourg showed (Chem. Eur. J. 2013, 19, 8765) that the alkenyl nosylate (p-nitrobenzenesulfonate) 25 coupled smoothly with 26, leading to the enyne 27. Reinhold Zimmer and Hans-Ulrich Reissig of the Freie Universität Berlin described (Synthesis 2013, 45, 2752) similar results with alkenyl nonaflates.

Renat Kadyrov of Evonik Degussa and Magnus Rueping of RWTH Aachen developed (Angew. Chem. Int. Ed. 2009, 49, 7556) an effective catalyst for the enantioselective hydrogenation of an α-hydroxy ketone 1 to the 1,2-diol 2 . Yong-Gui Zhou of the Dalian Institute of Chemical Physics showed (J. Org. Chem. 2009, 74, 5633) that a sultam such as 3 could be reduced with high ee to the sulfonamide 4. They also used this same approach to prepare both α-aryl and α,α-diaryl amines. David W. C. MacMillan of Princeton University described (Angew. Chem. Int. Ed. 2009, 49, 5121) the optimized enantioselective α-chlorination of an aldehyde 5 and the direct processing of the product to the epoxide 6. Erick M. Carreira of ETH Zürich reported (Synlett 2009, 2076) an alternative route to high ee epoxides by decarbonylation of an epoxy aldehyde 7. James P. Morken of Boston College established (J. Am. Chem. Soc. 2009, 131, 13210) a procedure for the enantioselective bis borylation of a terminal alkene 9, leading after oxidation to the 1,2-diol 10. Ben L. Feringa of the University of Groningen took advantage (J. Am. Chem. Soc. 2009, 131, 9473) of their alternative Wacker conditions to convert a primary allylic carbonate 11 to the protected β-amino aldehyde 12. Chao-Shan Da of Lanzhou University devised (Organic Lett. 2009, 11, 5578) additives that allow the direct enantioselective addition of a Grignard reagent 14 to an aldehyde. The enantioselective addition of substituted ketenes to aldehydes has long been established. Yun-Ming Lin of the University of Toledo developed (Synlett 2009, 1675) a catalyst system for the enantioselective addition of ketene 17 itself. An alkenyl silane 19 can readily be prepared from the corresponding terminal alkene (J. Org. Chem. 2010, 75, 1701). Koichi Mikami of the Tokyo Institute of Technology showed (J. Am. Chem. Soc. 2009, 131, 13922) that such alkenyl silanes add to ethyl glyoxylate 20 with high ee. Amir H. Hoveyda of Boston College devised (J. Am. Chem. Soc. 2009, 131, 18234) a procedure for the enantioselective conversion of a terminal alkyne 22 to the 1,2-bis boryl alkane, which he took on directly to the coupled product 24.

(-)-Pseudolaric acid B 3, isolated from the bark of the golden larch Pseudolarix kaempferi, shows potent antifungal activity. A key step in the total synthesis of 3 described (J. Am. Chem. Soc. 2008 , 130 , 16424) by Barry M. Trost of Stanford University was the free radical cyclization of 1 that established the angular ester and the trans ring fusion of 2 and thus of 3. To prepare the bicyclic skeleton of 1, the authors envisioned the Rh-mediated intramolecular addition of the alkyne of 11 to the alkenyl cyclopropane. The acyclic centers of 11 were established by Noyori hydrogenation of (equilibrating) racemic 4. One enantiomer reduced much more quickly than the other, leading to 5. The absolute configuration of the cyclopropane was set by Charette cyclopropanation of the monosilyl ether of the inexpensive diol 8. The two components were then coupled using a Corey-Schlosser protocol. Alkylation of the ylide 10 with 7 gave a new phosphonium salt, which in situ was deprotonated and condensed with the aldehyde 9 . The resulting betaine was deprotonated and quenched, then exposed again to base to give the trans alkene 11. It is important in this procedure to use PhLi as the base, because the alkyl lithium can displace the alkyl group on phosphorus. The product from Ru-catalyzed cyclization was the expected 1,4-diene 12 . Fortunately, it was found that TBAF desilylation led to concomitant alkene migration, to give the more stable conjugated diene 13. Selective epoxidation of the more electron-rich alkene fol lowed by exposure to strong base then delivered 14 , with the requisite angular oxygenation established. Pseudolaric acid B 3 would be derived from cyclization of the selenocarbonate of a tertiary alcohol. In fact, however, attempted cyclization of such selenocarbonates led only to decarboxyation and reduction. Even with the selenocarbonate 1 prepared from the secondary alcohol, the cyclization to 2 required careful optimization, including using not AIBN but azobis(dicyclohexylcarbonitrile) as the radical initiator. Acetylide addition to the ketone 15 could be effected with high diastereocontrol, but lactone construction proved elusive. Alkaline conditions led quickly to addition of the angular hydroxyl to the activated alkene in the seven-membered ring.