Novel Synthesis of Methylenecyclobutanols and 4-Methylenetetrahydrofurans from γ-Oxide Ylides
摘要:
The reaction of partial derivative-halo-gamma-oxide ylide, prepared from methylenetriphenylphosphorane and epichlorohydrin, with aldehydes afforded alkylidenecyclobutanols in moderate yields. The reaction initially proceeded through internal nucleophilic attack on partial derivative-carbon of this ylide. Another novel approach toward the synthesis of 4-methylenetetrahydrofurans was achieved by the reaction of gamma-oxide ylides with paraformaldehyde.
intramolecular substitutionreaction with alkoxide moiety occurs at the lithium alkylidene carbenoid center to give dihydrofurans. The reaction mechanism of this intramolecular substitutionreaction is studied by B3LYP density functional calculations with the 6-31+G(d) basis set, and the substitution is found to proceed in a concerted manner. This substitutionreaction is applied to the regioselective preparation
Intramolecular substitution reaction of geminal dibromo alkenes proceeds to afford indenes, dihydronaphthalenes, dihydrofurans, and dihydropyran via in situ generated lithium alkylidene carbenoids, which have a carbon or oxygen nucleophilic moiety. This reaction provides a regioselective method for the preparation of polysubstituted indenes.