Tandem Synthesis of 2-Azaspiro[4.5]deca-1,6,9-trien-8-ones Based on Tf₂O-Promoted Activation of N-(2-Propyn-1-yl) Amides

Abstract

Structurally novel 2-azaspiro[4.5]deca-1,6,9-trien-8-ones were synthesized from N-(2-propyn-1-yl) amides and 1,3,5-trimethoxybenzenes by a tandem method consisting of a Tf2O-promoted amide activation and a TfOH-promoted Friedel–Crafts ipso-cyclization. The method offered the first example of using N-(2-propyn-1-yl) amides as substrates in both Tf2O-promoted secondary amide activation and the synthesis of azaspiro[4.5]deca-6,9-diene-8-ones.