Synthesis of 1,1,2-Triarylalk-1-enes by desulphurization of 3,4-Diaryl-2H-1-benzothiopyrans

Abstract

3-Phenyl-1-thiochroman-4-one, and 7-methoxy-3-phenyl-1-thiochroman-4-one, obtained by cyclization of the appropriate 2-aryl-3-arylthiopropionic acids, were treated with p-methoxyphenyl- magnesium bromide or phenylmagnesium bromide, to give, after dehydration, 4-(p-methoxyphenyl)- 3-phenyl-2H-1-benzothiopyran and 7-methoxy-3,4-diphenyl-2H-1-benzothiopyran, respectively. Desulphurization with Raney nickel of 7-methoxy-3,4-diphenyl-2H-1-benzothiopyran, or 4-p-methoxyphenyl)-3-phenyl-2H-1-benzothiopyran gave mainly (E)- or (Z)-1-(p-methoxyphenyl)-1,2- diphenylprop-1-ene, respectively, with greater stereospecificity in the former reaction. (2)-1-(p- Methoxyphenyl)-1,2-diphenylprop-1-ene was the major product from the reaction of 4'-methoxy-2-phenylpropiophenone with phenylmagnesium bromide, followed by dehydration. Some other sulphur-containing compounds are described.