The Diels-Alder reaction, which is a traditional [4 + 2] cycloaddition with two carbon-carbon bond formations, is one of the most powerful tools to synthesize versatile and unique six-membered rings. We show that chiral supramolecular U-shaped boron Lewisacid catalysts promote the unprecedented multiselective Diels-Alder reaction of propargyl aldehyde with cyclic dienes. Independent from the substrate
Diels-Alder 反应是一种传统的 [4 + 2] 环加成反应,具有两个碳-碳键形成,是合成通用且独特的六元环的最强大工具之一。我们表明手性超分子 U 形硼路易斯酸催化剂促进了炔丙醛与环二烯前所未有的多选择性 Diels-Alder 反应。独立于底物控制,对映-、内/外-、π-面-、区域-、位点和底物选择性可以通过本 U 形催化剂进行控制。所得反应产物可用于手性二烯配体和(+)-沙霉素关键中间体的简明合成。这里介绍的结果可能部分有助于开发用于多选择性反应的人工酶样超分子催化剂,
A six-step total synthesis of α-thujone and d<sub>6</sub>-α-thujone, enabling facile access to isotopically labelled metabolites
The development of a short synthetic approach to [small alpha]-thujone enabled the first syntheses of its main metabolites in an isotopically labelled form.
作者:Johan du Toit、Demetrius C. Levendis、Jan C.A. Boeyens、Mohamed S. Loonat、Laurence Carlton、Wolfgang Pickl、Neil J. Coville
DOI:10.1016/0022-328x(89)85412-9
日期:1989.6
The complexes [(η5-C5H4R)Fe(CO)(PPh3)I] (R = I (1), CH(CH3)2 (2), CHPh2 (3)) have been synthesised. The NOE spectra recorded on the new complexes reveal a preferential conformation of the ring substituent on 3, with the H atom of the benzhydryl group pointing towards the PPh3 ligand. A similar effect is not observed in the spectrum of 2. The phenomenon is related to the steric effect associated with