4-Picoline-catalyzed hetero-Diels–Alder type reactions: one-pot synthesis of pyrano[4,3-c]chromenes

An organocatalytic hetero-Diels–Alder type reaction between α,β-unsaturated aldehydes and acetylenedicarboxylates is achieved which offers an efficient one-pot access to a new class of pyrano[4,3-c]chromenes from simple and readily available starting materials under mild reaction conditions.