Regioselective Carbon-Carbon Bond Formation in Titanium Mediated Reaction of Ethylmagnesium Bromide with Allylic Alcohols and Allylic Ethers
作者:Oleg G. Kulinkovich、Oleg L. Epstein、Vladimir E. Isakov、Ekaterina A. Khmel'nitskaya
DOI:10.1055/s-2001-9707
日期:——
In the presence of Ti(Oi-Pr)4 reaction of EtMgBr with allylic alcohols and allylicethers affords the products of formal SN2′ substitution of hydroxy or alkoxy groups with ethyl groups in moderate to good yields and excellent regioselectivity. The mechanism of the reaction includes the formation of titanacyclopropanes as the key organometallic intermediates. Promoting action of EtMgBr on the process
Oxidative free-radical cyclization of allylic α-chloromalonates. Synthesis of (±)-avenaciolide.
作者:Barry B. Snider、Bridget A. McCarthy
DOI:10.1016/s0040-4020(01)80213-1
日期:——
Oxidative free-radicalcyclization of α-chloromalonate 9 with Mn(OAc)3·2H2O and Cu(Oac)2·H2O in acetic acid at 75 °C provides 82% of lactones 10a and 10b. Hydroboration of 10 followed by oxidation affords acids 12, which are converted to avenaciolide precursor 15 in 32% overall yield from 9 by decarboxylation and cyclization.
Convergent synthesis of conjugated 1,2-disubstituted E-allylic alcohols from two aldehydes and methylenetriphenylphosphorane
作者:David M. Hodgson、Rosanne S. D. Persaud
DOI:10.1039/c2ob26346g
日期:——
β-Lithiooxyphosphonium ylides, made in situ from an aldehyde and methylenetriphenylphosphorane, react with a second aldehyde to form E-allylic alcohols. α-Branching and α,β-unsaturation in the second aldehyde, together with the lack of further substitution on the phosphorane carbon play important roles in selectivity. A range of these aldehydes, in addition to aromatic aldehydes as the second aldehyde also provided synthetically useful access to E-allylic alcohols.