Novel metal-free hydrogenation of the carbon-carbon double bond in azulenoid enones by use of cycloheptatriene and protic acid

[reaction: see text] An efficient method for the hydrogenation of the carbon-carbon double bond in azulenoid and aromatic fused azulenoid enones without the use of hydrogen and a metal catalyst is reported. Treatment of a variety of azulenoid enones with cycloheptatriene and a protic acid in acetonitrile gave the corresponding beta-azulenyl ketone derivatives in excellent to moderate yield. In this reaction, cycloheptatriene acts as a hydride donor.