Organophosphorus compounds. Part 144: A novel approach to 1,3-oxaphospholes from phosphaalkynes and isomunchnones

Phosphaalkynes 5 react with the isomunchnones 12 in a regiospecific process to furnish the 1,3-oxaphospholes 14. In contrast to other cycloadditions t o isomunchnones, the bicyclic intermediate 13 cannot be detected in these r eactions. It is not necessary to use isolated isomunchnones 12 for the synt hesis of the 1,3-oxaphospholes. The reaction sequence is also successful by use of the diazocarbonyl compounds 11 and in situ generation of the isomun chnones therefrom. (C) 1999 Elsevier Science Ltd. All rights reserved.