Cyclones, reaction with dichlorocarbene

The reaction of dichlorocarbene with the fused-ring cyclone (Scheme 7.15) follows an unusual pathway. After initial reaction at the C=C bond, further attack occurs at the carbonyl group. Ring-opening of the oxirane, followed by decarboxylation (see Section 7.4) leads to the final product in 52% yield [73]. 

The production of buta-1,3-dienes (37) by reaction of 1,2-diarylcyclopropenes with dihalocarbenes is thought to involve electrophilic attack of the carbene to give a dipolar intermediate (38).51 The addition of carbene to CO and H2C=0 has been studied by MNDO calculations.52 Photolysis of diethyl diazomalonate in a CO matrix at low temperature gave rise to ketenes by immediate trapping of the postulated carbene (39).53 The major products of reaction between dichlorocarbene and cyclone were CO and the gem-dichloro species (40).54 The predominance of this pathway over formation of the dichlorooxirane or the cyclopropane is attributed to the aromatic nature of the carbonyl ylide and its twist geometry. 

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See also in sourсe #XX -- [ ]

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