Stereoselective Synthesis of 3-Oxygenated-cis-dialkyl-2,5-substituted Tetrahydrofurans from Cyclohexadienediols
摘要:
The 3-oxygenated-cis-dialkyl-2,5-substituted tetrahydrofuran system, present in several natural products, was prepared with good selectivity by acidic cyclization of 5-alkene-1,2,4-triol derivatives. The starting alkenol was obtained in few steps from a chiral cis-diol resulting from microbial oxidation of bromobenzene. The study of the cyclization allowed the rationalization of all experimental results by assuming a complete ionization at the allylic position and a model close to the one proposed by Labelle for homoallylic induction in five-membered ring closures.
Selectivity in the halohydroxylation of cyclohexadienediols
作者:Ignacio Carrera、Margarita C. Brovetto、Gustavo Seoane
DOI:10.1016/j.tet.2007.02.109
日期:2007.5
The halohydroxylation of a number of cyclohexadienediol derivatives has been investigated. The selectivity of the reaction as a function of the type of substituent on the diene, protecting group of the diol functionality, halonium donor, medium polarity, and temperature is described. Best selectivity is obtained for iodohydrin formation. The course of the reaction for these dienic systems is heavily dependent on steric factors. (C) 2007 Elsevier Ltd. All rights reserved.