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Unusual Intramolecular [2 + 2] Cycloaddition of Allyl and Vinylidene CC Bonds under Mild Conditions:  A Theoretical Analysis

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journal contribution
posted on 02.04.2004, 00:00 by Pedro Braña, José Gimeno, José A. Sordo
A theoretical analysis allows for the rationalization of the recently reported unusual formation under mild conditions of a cyclobutylidene ring from a diastereoselective [2 + 2] intramolecular cycloaddition of two CC systems. The reaction takes place by heating in dichloromethane the vinylidene complexes [Ru((η53-C9H7){CC(R)H}{κ1-(P)-PPh2(C3H5)}(PPh3)][BF4] (R = Ph, p-Me-C6H4) (1) yielding the bicyclic alkylidene complexes (2). The proposed mechanism represents an alternative to the classical Woodward−Hoffmann's supra-antara approach.