Asymmetric Diels–Alder reactions. Part 3. Influence of butadiene structure upon the diastereofacial reactivity of (E)-1-(2′,3′,4′,6′-tetra-O-acetyl-β-D-glucopyranosyloxy)buta-1,3-dienes

Abstract

(E)-1-(2′,3′,4′,6′-Tetra-O-acetyl-β-D-glucopyranosyloxy)buta-1,3-diene (1c), its 3-methyl derivative (1d), its 2,3-dimethyl derivative (1e), its (3Z)-4-acetoxy-3-(t-butyldimethylsilyloxy) derivative (1f), its 3-(t-butyldimethylsilyloxy) derivative (1g), and its (3Z)-3-(t-butyldimethylsilyloxy)-2,4-dimethyl derivative (1h) have been prepared and their diastereofacial reactivities towards N-phenylmaleimide and tetracyanoethylene assessed. With the former dienophile in benzene at ambient temperature, the dienes (1c, d, f, g) gave ca. 87 : 13 mixtures of the cycloadduct pairs (2c) and (3c), (2d) and (3d), (2f) and (3f), and (2g) and (3g); however, the dienes (1e, h) afforded only the cycloadducts (2e, h). With tetracyanoethylene in benzene at ambient temperature, the aforecited dienes reacted to give mixtures of cycloadducts, ranging from a 69 : 31 mixture of the cycloadducts (6c) and (7c) in the case of the diene (1c) to an 89 : 11 mixture of the cycloadducts (6h) and (7h) in the case of the diene (1h).