Reactions of unsaturated acid halides. Part III. Aluminium chloride-catalysed reactions of cinnamoyl chloride with benzene

Abstract

Re-investigation of the reaction between cinnamoyl chloride, a small excess of aluminium chloride, and benzene at 80° has confirmed that the main product is ββ-diphenylpropiophenone together with 3-phenylindanone and ββ-diphenylpropionoyl chloride. The following minor products not previously identified were also found: acetophenone, diphenylmethane, and benzene-1,4-bis-[3-(3-phenylpropiophenone)], no chalcone was isolated. From the suggested reaction path described here the extent of cinnamoylation was estimated to be about six times that of addition of benzene to the ethylenic bond in the cinnamoyl chloride.

Although re-investigation of a homogeneous reaction at room temperature between the unsaturated acid chloride and a large excess of benzene, in the presence of chlorobenzene and 1 mol. of the catalyst, confirmed that the products consisted mainly of chalcone, the yield of this compound after 8 hr. was low. A similar homogeneous reaction, conducted at 80° for 2 hr. without chlorobenzene, however, gave an 85% yield of chalcone, together with a trace of 3-phenylindanone. The formation of products other than chalcone is attributed to the presence of uncombined aluminium chloride.