A new general route to 1,2-diarylethylenes, 1,4-diarylbutadienes and 1,6-diarylhexatrienes through cycloaromatization of β-oxodithioacetals

A new general route for the title olefins 5a-e, 12, 13, 8a-e and 11a-e has been developed through nucleophilic addition of respective Grignard reagents i.e. allyl-, benzyl-, 1-(naphthylmethyl) magnesium halides to 5-aryl- 1,1-bis(methylthio)pent-4-en-3-ones, 7-aryl-1,1-bis(methylthio)hepta-4,6-dien-3-ones and 9-phenyl-1, 1-bis(methylthio)nona-4,6,8-trien-3-one followed by cycloaromatization of the resulting 3-substituted 1,1-bis(methylthio)alken-3-ols in the presence of boron trifluoride-diethyl ether complex