ChemInform Abstract: Photoinduced Molecular Transformations. Part 100. Formation of Furocoumarins and Furochromones via a β-Scission of Cyclobutanoxyl Radicals Generated from (2 + 2)Photoadducts from 4-Hydroxycoumarin and Acyclic and Cyclic Alkenes. X-Ray Crystal Structures of (6aα,6bα,9aα,9bα)-(.+-.)-6b,7,8,9,9a,9b-Hexahydro-9b-hy# droxybenzo(b)cyclopenta(3,4)cyclobuta-(1,2-d)pyran-6(6aH)-one, cis-(.+-.)-6b,8,9,9a-Tetrahydro-6H,7H-cyclopenta-(4,5)furo(3,2-c)(1)benzopyran-# 6-one, and cis-1,2,2a,8b

ChemInform Abstract

Irradiation of the fused cyclobutanols (I), (IV), and (IX) in the presence of mercury(II) oxide and iodine yields the furocoumarins (II), (V), and (X). The additional products (IIIc) and (VI) are obtained from (Ic) and (IV). Photocycloaddition of 4-hydroxycoumarin (VII) with isopropenyl acetate (VIII) gives the fused acetoxycyclobutanol (IX). The formation of further furocoumarins and furochromones is described in the original paper. (Intermediates, mechanism, crystal data of (IV)).