

A FORMAL [4+1] CYCLOADDITION OF DIMETHOXYCARBENE TO 3-PERFLUOROACYL-4H-CHROMENES: THE SYNTHESIS OF ARENO-CONDENSED 7,7a-DIHYDRO-4H-FURO[3,4-b]PYRANS

Abstract
The [4+1] annulation of in situ generated dimethoxycarbene to 3-trifluoroacetyl-4H-chromenes led to cyclic ortho esters, trifluoromethyl-substituted dihydrofuro[3,4-b]chromenes. In the case of 2-perfluoroacyl-1H-benzo[f]chromenes, representatives of a new heterocyclic system 7a,8-dihydro-11H-benzo[f]furo[3,4-b]chromene, were formed.
Keywords
dihydrofuro[3,4-b]chromenes; dimethoxycarbene; 3-perfluoroacyl-4H-chromenes; Warkentin's oxadiazoline; [4+1] cycloaddition.
Latvian Institute of Organic Synthesis - Aizkraukles iela, 21, Riga, LV-1006, Latvia - hgs@osi.lv