Chemoselective, Regioselective, and <i>E</i>/<i>Z</i>-Diastereoselective Synthesis of 2-Alkylidenetetrahydrofurans by Sequential Reactions of Ambident Dianions and Monoanions
作者:Peter Langer、Esen Bellur
DOI:10.1021/jo034966f
日期:2003.12.1
A number of novel beta-ketoesters were prepared by regioselective alkylation reactions of simple beta-ketoester dianions. The cyclization of the dianions of these 1,3-dicarbonyl derivatives with 1-bromo-2-chloroethane afforded a variety of 2-alkylidenetetrahydrofurans with very good regioselectivity and E/Z-diastereoselectivity. These products were deprotonated to give novel ambident carbanions. The
2-(1-Alkoxycarbonyl)alkylidenetetrahydrofurans were readily synthesized by the codimerization of 2,3- or 2,5-dihydrofurans with α,β-unsaturated esters using a zerovalent Ru catalyst, Ru(cod)(cot), with high regio- and stereoselectivity.
Reaction of 2-Alkylidenetetrahydrofurans with Boron Tribromide: Chemo- and Regioselective Synthesis of 6-Bromo-3-oxoalkanoates by Application of a ‘Cyclization-Ring-Opening’ Strategy
作者:Peter Langer、Esen Bellur
DOI:10.1055/s-2004-830893
日期:——
Bromo-3-oxoalkanoates, benzofurans and 1,7-dibro- moheptan-4-ones were chemo- and regioselectively prepared by reaction of 2-alkylidenetetrahydrofurans with borontribromide.