Synthesis of Trifluoromethylated 4 H -Pyran and 4 H -Thiopyran via Divergent Reaction of β-CF 3 -1,3-Enynes with β-Ketothioamides.

A chemodivergent tandem intermolecular hydrocarbonation and intramolecular oxy- or thioheterocyclization sequence of β-CF 3 -1,3-enyne with β-ketothioamides (KTAs) leading to ring-trifluoromethylated 4 H -pyran or 4 H -thiopyran, respectively, by the combined use of AgNO 3 as a catalyst and Et 3 N as a base was developed. A remarkable substituent effect was observed. The substituent on either the keto moiety or the nitrogen atom of β-ketothioamides has a great impact on the chemoselectivity. Enynes possessing electron-withdrawing aryl groups on the alkyne moiety are generally good candidates for the present transformation.