Organophosphorus Compounds. Part 144: A Novel Approach to 1,3-Oxaphospholes from Phosphaalkynes and Isomünchnones

Phosphaalkynes 5 react with the isomünchnones 12 in a regiospecific process to furnish the 1,3-oxaphospholes 14. In contrast to other cycloadditions to isomünchnones, the bicyclic intermediate 13 cannot be detected in these reactions. It is not necessary to use isolated isomünchnones 12 for the synthesis of the 1,3-oxaphospholes. The reaction sequence is also successful by use of the diazocarbonyl compounds 11 and in situ generation of the isomünchnones therefrom.