Diels–Alder reactions of alkyl-substituted dienes with acrylonitriles give good yields and endo-selectivities if catalyzed by (organo)aluminum, (organo)boron or gallium halides. The activity of these group IIIa Lewisacids in this reaction correlates with the coordination strength of their nitrile complexes, which deactivate Lewisacids sufficiently, so that the subsequently added diene partner undergoes
Hydrosilylation of 1-vinylcycloalkenes with methyldichlorosilane in the presence of a palladium catalyst proceeded with high regio- and stereoselectivity to give (Z)-1-ethylidene-2-silylcycloalkanes in high yields.
Development of Synthetic Routes to <scp>d</scp>,<scp>l</scp>-α-Tocopherol (Vitamin E) from Biologically Produced Geranylgeraniol
作者:John A. Hyatt、Gregg S. Kottas、Janet Effler
DOI:10.1021/op020216g
日期:2002.11.1
isophytol as a side-chain synthon for producing d,l-α-tocopherol. Two routes were studied, both of which begin with allylic epoxidation followed by olefin hydrogenation to give epoxyphytol. Epoxyphytol can be reduced with Red-Al to provide phytan-1,3-diol which upon acid-catalyzed condensation with trimethylhydroquinone gives vitaminE in fair yield. In a higher-yielding process, epoxyphytol was deoxygenated
探索了使用生物衍生的二萜醇香叶基香叶醇作为基于石油化学的异植醇的替代品,作为用于生产 d,l-α-生育酚的侧链合成子。研究了两条路线,均以烯丙基环氧化开始,然后烯烃氢化得到环氧植醇。环氧植物醇可以用 Red-Al 还原以提供植烷-1,3-二醇,其在酸催化下与三甲基氢醌缩合以合理的收率生成维生素 E。在更高产率的过程中,环氧植醇与三氧化甲基铼/三苯基膦脱氧,生成植醇和异植醇的混合物(来自香叶基香叶醇的产率 > 90%)。这种混合物可以作为异植醇的“插件”替代品,用于目前实施的维生素 E 化学的最后一步。
Regio-and stereo-selection reaction of 1,3-dialkyl-substituted allyl anions with aldehydes viaη<sup>3</sup>-allyltitanium compounds
作者:Yuichi Kobayashi、Kensuke Umeyama、Fumie Sato
DOI:10.1039/c39840000621
日期:——
The Regio-and stereo-chemistry in reaction of 1,3-dialkyl-substitutedallylanions with aldehydes is controlled viaη3-allyltitanium compounds, thus providing a simple method for preparation of cycloalkanes having a 1- hydroxyalkyl side chain.
Cationic-Oxazaborolidine-Catalyzed Enantioselective Diels-Alder Reaction of α,β-Unsaturated Acetylenic Ketones
作者:Joshua N. Payette、Hisashi Yamamoto
DOI:10.1002/anie.200904339
日期:2009.10.12
Yne also a good dienophile: The cationic oxazaborolidine 1 promoted the formation of Diels–Alder adducts between acetylenic ketones and both cyclic and acyclic dienes in excellent yield with 99 % ee (see scheme; Tf=trifluoromethanesulfonyl, TMS=trimethylsilyl). Importantly, high levels of asymmetric induction were also observed with dienophiles that lacked the typical hydrogen‐bonding motif required