NHC-catalyzed formal [3 + 3] annulations of δ-acetoxy allenoates for the synthesis of 4 H -pyran derivatives.

Herein, an N-heterocyclic carbene (NHC) catalyzed formal [3 + 3] annulation of δ-acetoxy allenoates with 1C,3O-bisnucleophiles for the construction of 4 H -(fused)pyrans has been developed. This protocol provides a facile method to synthesize highly functionalized 4 H -pyrans and has a broad substrate scope (30 examples, up to 77% yield).