Insertion reactions of alkenes with diterpenoid chromium aminocarbenes

Insertion reactions of electron-deficient alkenes with chromium aminocarben es derived from podocarpic acid generally give aryl ketone products derived from ring opening of an aminocyclopropane and subsequent enamine hydrolysi s, the exception being alkenyl sulphones which give products derived from i nsertion of the carbene into the P-CH bond of the alkene. Increasing steric hindrance due to the substituents on the aminocarbene nitrogen appears to result in higher yields of the insertion products. However, other factors s uch as stabilisation of the intermediate tetracarbonylaminocarbene may expl ain why morpholinocarbenes give superior yields of the insertion products. Propenoic acid, propenal or nitropropene give a 13-formyl-substituted diter penoid. Electron-rich alkenes do not undergo insertion reactions with these aminocarbenes at 110 degreesC. (C) 2001 Elsevier Science B.V. All rights r eserved.