ORGANOPHOSPHORUS CHEMISTRY 25.¹ THE UTILIZATION OF WITTIG REAGENTS IN LACTONE RING FORMATION. APPLICATION TO THE SYNTHESIS OF LINEAR FUROCOUMARINS AND PYRANOCOUMARINS

Abstract

A new and improved method for the preparation of linear furocoumarins (7a,b) and pyranocoumarins (10a,b) in high yields, is described. It depends upon reacting ylid-phosphoranes (5) with suitably substituted benzofuran-, (3) or the benzo-γ-pyrone-(4) moiety. Formation of the target compounds (7 and 10) is assumed to proceed via lactonization of cis alkyl α-hydroxycinnamate intermediates of types 6 and 9, respectively. The trans analogues 8 do not lactonize to 10 even upon heating in boiling toluene. The new compounds have been characterized by their spectroscopic data (IR, PMR, ¹³C NMR) and elementary analyses.

Key Words:

• Wittig-reaction
• lactonization
• preparation of linear furocoumarins
• pyranocoumarins.