Asymmetric addition of (triisopropylsilyl)acetylene to α,β,γ,δ-unsaturated carbonyl compounds took place in the presence of a cobalt/Duphos catalyst to give the 1,6-addition products in high yields with high regio- and enantioselectivity.
To the point: The rhodium‐catalyzed asymmetricconjugatealkynylation of α,β‐unsaturated aldehydes with triisopropylsilyl acetylene proceeded efficiently in methanol to give the β‐alkynyl aldehydes in high yields with high enantioselectivity (see Scheme).
Application of a Domino Intramolecular Enyne Metathesis/Cross Metathesis Reaction to the Total Synthesis of (+)-8-<i>e</i><i>pi</i>-Xanthatin
作者:David A. Kummer、Jehrod B. Brenneman、Stephen F. Martin
DOI:10.1021/ol051711a
日期:2005.10.1
[reaction: see text] The first total synthesis of the novel sesquiterpene lactone (+)-8-epi-xanthatin (1) has been achieved starting from the commercially available ester 8. The synthesis features an asymmetric aldol reaction and palladium-catalyzed carbonylation/lactonization sequence leading to 4 and a domino ring-closingenynemetathesis/crossmetathesisreaction to afford 1.
catalyzed tandem allylboration/lactonization reaction is reported. With (+)‐8‐epi‐xanthatin as the precursor, the collective synthesis of a series of synthetically challenging xanthanolides was also accomplished. Among them, xanthipungolide, one of the most complex xanthanolide monomers, was accessed through a bioinspired tandem double‐bond isomerization/6π electronic cyclization/intramolecular Diels–Alder