Synthesis of 6-substituted 4-hydroxy-2-pyrones from aldehydes by addition of an acetoacetate equivalent, Dess-Martin oxidation and subsequent cyclization

A three step procedure for the synthesis of 6-substituted 4-hydroxy-2-pyrones 2 from aldehydes 1 is described. An acetoacetate equivalent 3 was added to the corresponding aldehyde (10 examples) in a vinylogous Mukaiyama aldol addition (72-99%). The intermediate alcohols 4 were oxidized to the ketones 5 using the Dess-Martin method (67%-quant,). A final thermal cyclization of compounds 5 yielded the title compounds 2 (61-92%; 40-85% overall).