Regioselective preparation of diethyl 3,4-disubstituted 1,5-dihydro-5-oxo-2H-pyrrol-2-ylphosphonates and their coupling with aldehydes. Application to the synthesis of C/D-rings component of phycocyanobilin

Article abstract of DOI:10.1246/bcsj.67.3320

Diethyl 3,4-disubstituted 1,5-dihydro-5-oxo-2H-pyrrol-2-ylphosphonates were regioselectively prepared by acidic hydrolysis of diethyl 3,4-disubstituted 5-bromo-2-pyrrolylphosphonates. The resulting 1,5-dihydro-2H-pyrrol-2-ones readily underwent the coupling reaction with various reaction with various aldehydes to afford the corresponding 1,5-dihydro-5-methylene-2H-pyrrol-2-ones including pyrromethenone derivatives in good yields. A series of these reactions was successfully applied to the synthesis of C/D-rings component of phycocyanobilin.