A highly efficient rhodium(III)‐catalyzed directoxidative annulation of acrylicacid with alkynes to form α‐pyrones was developed. Various substituted acrylicacids were compatible in this transformation, affording the corresponding products in moderate to excellent yields under mild conditions.
Abstract A simple procedure for the synthesis of 2H-pyran-2-ones 1 is described: selective Wittig olefination of keto aldehydes at the aldehyde group followed by a cyclization in acidic medium.
The dehydrogenative coupling of maleic acids with alkynes proceeds smoothly accompanied by decarboxylation under rhodium catalysis to produce variously substituted a-pyrone derivatives. The catalyst system is also applicable to the coupling with 1,3-diynes and alkenes.
Sacharkin; Sorokina, Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, 1958, p. 1445,1447; engl. Ausg. S. 1393, 1395