Diels-Alder Reactions of (Trifluoromethyl)ethene and (Trifluoromethyl)styrenes with Functionalized Butadiens

Article abstract of DOI:10.1021/jo00132a015

The-Alder reactions of (trifluoromethyl)ethene (1) with 2-(trimethylsiloxy)buta-1,3-diene (2), 2-<(trimethylsilyl)methyl>-1,3-butadiene (4), and 1-methoxy-3-(trimethylsiloxy)buta-1,3-diene (6) were carried out to give the corresponding <4+2> cycloadducts in 17-38percent yields.It was found that the former two cycloadducts were a mixture of para (major) and meta (minor) isomers, while the latter was the para isomer exlusively.Similary, β-(trifluoromethyl)-4-(methoxycarbonyl)styrene (9) and β-(trifluoromethyl)-4-nitrostyrene (10) were allowed to react with 4 and 6, giving the corresponding <4+2> cycloadducts in 56-90percent yields.The regioselectivity of the reaction on using 6 as the diene turned out to be extremely high, leading to the formation of only one regioisomer.The substituent effect of the trifluoromethyl group in the Diels-Alder reaction in terms of regioselectivity is discussed.