2-alken-4-ynoate ester 1-alkyne

Ethyl 4.4,4-trifluorobut-2-ynoate reacts with various dienes (Table 3). " With a iionsymmctric diene, the cycloadduct is obtained as a mixture of regioisomers. This suggests that, unlike reactions with alkenes, reactions with alkynes arc not governed by the ester substituent. Cycloadducts can also undergo a further cycloaddition, in particular when the diene is used in excess. 

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