Enantioselective Cyclopropanation of Allylic Alcohols with Dioxaborolane Ligands: Scope and Synthetic Applications
作者:André B. Charette、Hélène Juteau、Hélène Lebel、Carmela Molinaro
DOI:10.1021/ja982055v
日期:1998.11.1
the conversion of allylicalcohols into the corresponding enantiomerically enriched cyclopropanes using bis(iodomethyl)zinc. A variety of chiral, nonracemic cyclopropylmethanols could be obtained according to this method. This methodology was extended with success to the cyclopropanation of unconjugated and conjugated polyenes and homoallylic alcohols. The cyclopropanation of allylic carbamates has also
In tandem reactions, cyclopropylcarbinols are obtained from allyloxylithium or -magnesium intermediates, generated in situ by alkylation of conjugated aldehydes, ketones, and esters as well as from allyl carboxylates or vinyloxiranes. Using this methodology, numerous fragrance ingredients and their precursors were efficiently converted to the corresponding cyclopropylcarbinols.
from α-substituted (homo)allyl alcohols. In tandem reactions, cyclopropyl carbinols are obtained from allyloxylithium or -magnesium intermediates, generated in situ by alkylation of conjugated aldehydes, ketones, and esters as well as from allyl esters and carbonates or vinyloxiranes. [¹] cyclopropanation - Barbier conditions - Grignard addition - alkyllithiumaddition - dibromomethane
Chemoselective and stereoselective lithium carbenoid mediated cyclopropanation of acyclic allylic alcohols
作者:M. J. Durán-Peña、M. E. Flores-Giubi、J. M. Botubol-Ares、L. M. Harwood、I. G. Collado、A. J. Macías-Sánchez、R. Hernández-Galán
DOI:10.1039/c5ob02617b
日期:——
and the corresponding dihaloalkane has been evaluated. The reaction occurs in a chemo and stereoselective manner, which is consistent with a directing effect from the oxygen of the allylic moiety. Furthermore, a set of polyenes containing allylic hydroxyl or ether groups were chemoselectively and stereoselectively converted into the corresponding gem-dimethylcyclopropanes in one single step in moderate
[EN] CYCLOPROPANATION PROCESS<br/>[FR] PROCÉDÉ DE CYCLOPROPANATION
申请人:GIVAUDAN SA
公开号:WO2009023980A1
公开(公告)日:2009-02-26
A method for the preparation of cyclopropyl carbinols by cyclopropanation of unsaturated alcoholates, utilising a reagent system selected from (A) magnesium metal and dibromomethane, and (B) dibromomethane and a tertiary Grignard reagent, the reaction being carried out in the presence of an ether solvent. The process is useful, for example, for the preparation of ingredients for the flavour and fragrance industry.