Abstract
Abstract The α-oxoketene dithioacetals of general formula 1 (Scheme 2), undergo regioselective 1,2-addition with allyl anions to afford the corresponding carbinol acetals 6 in quantitative yields, which on treatment with BF3.Et2O in refluxing benzene yield the corresponding aromatic systems. The method has been shown to be widely applicable as exemplified by a large number of allyl anions (Scheme 3) reacting with α-oxoketene dithioacetals with wide structural variation. However, when 1 carry the α-substituent the intermediate carbinol acetals 14 (Scheme 4) follow, different path to yield the corresponding indenes 15 in good yields. The cinnamoylketene dithioacetals 16 react with allyl anions to afford the corresponding methylthiostilbenes 18 (Scheme 5), while the homologous dithioacetal 20 failed to yield the corresponding 1,4-biaryl-1,3-diene 22 (Scheme 6). This limitation was circumvented by reacting 23 with allyl anions to afford the corresponding stilbenes 24, dienes 25 and triene 26 respectively. The...
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