Carbonyl and thiocarbonyl compounds. Part XIV. Reactions of tetrachloro-o-benzoquinone with 3-(2-furyl)- and 3-(2-thienyl)-acrylophenones

Abstract

Tetrachloro-o-benzoquinone readily undergoes 1,4-cycloaddition with the furyl residue of 3-(2-furyl)acrylophenones to give the 1 : 1 adducts (2). Further addition to the electrophilic double bond of the side chain to give the 2 : 1 adducts (6a–c) requires drastic conditions. In contrast, addition to the side chain of the 3-(2-thienyl)acrylophenones (1d–f) readily gives the 1 : 1 adducts (3a–c), with the thiophen ring unmodified. Adducts (3a–c) form hydrazones and oximes, and the latter react with isocyanates affording oxime carbamates (3k–m) of possible pesticidal importance. The adducts (2a–c) react with benzylmagnesium chloride to give the expected β-benzyl adducts (6a–c), whereas with phenylmagnesium bromide concomitant cleavage of the dioxan ring occurs to give the 3-(2-furyl)-3-phenylpropiophenones (7a–c).