The nucleophilic attack of substituted anilines at position 6 of methyl coumalate (1) opens the α‐pyrone ring to form 4‐arylamino‐3‐(methoxycarbonyl)butadien‐1‐carboxylic acid 2 (Scheme 1). The latter are easily decarboxylated at room temperature in polar aprotic solvents to 1‐arylamino‐2‐(methoxycarbonyl)butadiene 4 which smoothly undergo regio‐ and stereospecific Diels‐Alder reactions with different dienophiles.
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Kvita et al. (1983) studied this question.
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