Cyclopropane, alkene-like reactions rearrangement

Abstract The photoinduced reactions of metal carbene complexes, particularly Group 6 Fischer carbenes, are comprehensively presented in this chapter with a complete listing of published examples. A majority of these processes involve CO insertion to produce species that have ketene-like reactivity. Cyclo addition reactions presented include reaction with imines to form /1-lactams, with alkenes to form cyclobutanones, with aldehydes to form /1-lactones, and with azoarenes to form diazetidinones. Photoinduced benzannulation processes are included. Reactions involving nucleophilic attack to form esters, amino acids, peptides, allenes, acylated arenes, and aza-Cope rearrangement products are detailed. A number of photoinduced reactions of carbenes do not involve CO insertion. These include reactions with sulfur ylides and sulfilimines, cyclopropanation, 1,3-dipolar cycloadditions, and acyl migrations. 

The cationic rearrangement of cyclobutyl compounds to cyclopropylmethyl derivatives is a well-studied reaction which, like the homoallylic rearrangement, has been mainly investigated in connection with the fate and nature of the cyclobutyl cation.Again the synthetic value of this rearrangement is limited because generally mixtures of cyclobutanes, cyclopropanes and alkenes are obtained. 

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