Abstract
Selenoxanthene 10-oxides (5a-d) reacted with methyl propiolate, dimethyl and diethyl acetylenedicarboxylates to afford selenoxanthen-10-io [formyl (or alkoxalyl) alkoxycarbonyl]-methanides (6a-i). The 9-isopropyl derivative gave only trans-ylides and the 9-phenyl congener formed cis-and trans-ylides. The stereochemistry is discussed on the basis of the nuclear magnetic resonance spectral data. Reduction of the selenoxanthenium ylides with sodium borohydride afforded the ylide lactones (16a-c) and the ylide alcohols (17a-f). The product ratio depended on the solvent used.
