Chiral allyl cations are captured by furan with 100% stereoselectivity: synthesis of enantiopure 2-alkoxy-8-oxabicyclo
A low-temperature (-95 degrees C) protocol for intermolecular cycloadditions of furan to chiral silyloxyallyl cations in dichloromethane is described. Key precursors are open-chain, mixed a-ketoacetals, which are chiral. The resulting [4+3] cycloadducts are densely functionalized and are isolated as single enantiomers in high chemical yield. The yield of the cycloadducts increases with increasing dilution. Three and four stereogenic centres are created in one single step.
Stark
CB
Department of Organic Chemistry, University of Hannover, Germany.
Pierau
S
Wartchow
R
Hoffmann
HM