114. P. Müller, C. Gränicher,
     “Structural Effects on the Rh^II-Catalyzed Rearrangement of Cyclopropenes”
     Helv. Chim. Acta 1993, 76, 521-534.

The thermocatalytic rearrangement of 2-alkylcycloprop-2-ene-1-carboxylates (1) in the presence of Rh^II perfluorobutyrate is regio- and stereospecific and leads to the substituted metallocarbenes 3. The latter undergo intramolecular C?H bond insertion to form cyclopentylidenes (4). In contrast, the metallocarbenes 19, derived from 2,3-dialkylcycloprop-2-ene-1-carboxylates 6c, d, react to dienes (Z)-20, via 1,2-H migration. The cyclopropenedicarboxylates 10, in turn, rearrange exclusively to the more substituted metallocarbenes 26, which cyclize to furans 28, With 6e, and 12, products derived from both modes of ring-opening are observed.

DOI : 10.1002/hlca.19930760134 

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