Diels-Alder type syntheses with hetero enes

Hetero-Diels-Alder reactions performed with trifluoromethyl-substituled heterodienes or with trifluoromcthyl-substituted heterodienophiles have resulted in the synthesis of a large number of fluoro-heterocyclic compounds. Ketones, thioketones, imincs, nitriles, and their parent a,/3-unsaturated systems have been studied in cycloaddition reactions. Cycloadditions are regioselec-tive. An interesting aspect is the competition with ene-type reactions, aldol reactions and, depending on the partners, with [2 + 2]-cycloaddition reactions. 

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