Diazo ketones vinylogous Wolff rearrangement

With 0,-y-unsaturated a -diazo ketones, the resulting [2.1.0]-bicyclic systems (40) were quite unstable and underwent a [2 + 2] cycloreversion to generate ketenes (41), which were then trapped by nucleophiles (Scheme 7). The overall scheme has been named a vinylogous Wolff rearrangement and offers a novel entry to products usually derived from a Claisen rearrangement.102 A recent report describes its application for functionalized angular alkylation in fused ring systems.103 In contrast, the intramolecular re-... 

Ceccherelli, P., Curini, M., Marcotullio, M. C., Rosati, O. Dirhodium tetraacetate-catalyzed decomposition of 3,Y-unsaturated diazo ketones a new entry to vinylogous Wolff rearrangement. Gazz. Chim. Ital. 1994,124,177-179. 

Angularly functionalized polycyclic systems may be prepared from /3,)/-unsaturated diazo ketones by a vinylogous Wolff rearrangement in the presence of coppCT(II) triflate. Dry copper(II) acetylacetonate is equally suitable. 

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