Titanocene-promoted stereoselective eliminations on epoxy alcohols derived from R-(−)-carvone
摘要:
The reaction of several stereoisomeric epoxy alcohols, obtained from R-(-)-carvone, and their corresponding formates, acetates, and benzoates, promoted by Cp2TiCl has been studied. The different outcomes of the reaction of epoxy derivatives are rationalized in terms of mechanistically biased processes. The radicals emerging from oxirane cleavage provide two types of reaction: dehydroxylation (deoxy-carbonylation) and dehydrogenation.The results offer considerable support for the radical elimination theory of hydroxyl, formyloxyl, and acetoxyl groups. The inability of tertiary radicals to be reduced by the Ti(III) complex is demonstrated unequivocally. (c) 2012 Elsevier Ltd. All rights reserved.
Non-natural Elemane as the “Stepping Stone” for the Synthesis of Germacrane and Guaiane Sesquiterpenes
作者:Elissavet E. Anagnostaki、Alexandros L. Zografos
DOI:10.1021/ol3031999
日期:2013.1.4
utilization as a common synthetic scaffold to produce structurally diverse germacrane and guaiane sesquiterpenes are described. A highly enantio- and stereoselective biomimetic tandem oxy-Cope/ene rearrangement was used as the key reaction to access the 10-membered macrocyclic core of germacranes and the condensed 5–7 carbocycles of guaiane sesquiterpenes. Additionally, reactions of furanoguaianes under acidic