Carbenes reactions with heterocycles

Furan and thiophene undergo addition reactions with carbenes. Thus cyclopropane derivatives are obtained from these heterocycles on copper(I) bromide-catalyzed reaction with diazomethane and light-promoted reaction with diazoacetic acid ester (Scheme 41). The copper-catalyzed reaction of pyrrole with diazoacetic acid ester, however, gives a 2-substituted product (Scheme 42). 

The reactions of carbenes, which are apparently unique in displaying electrophilic character in strongly basic solutions, include substitution, addition to multiple bonds, and co-ordination with lone pairs of electrons to form unstable ylides. This last reaction is of obvious relevance to a consideration of the reactions of heterocyclic compounds with carbenes and will be summarized. 

The Reactions of Heterocyclic Compounds with Carbenes C. W. Rees and C. E. Smithen... 

For a review of the reactions of heterocyclic compounds with carbenes, see Rees Smithcn Adv. Heterocycl. Chem. 1964, 3, 57-78. 

Rees, C.W. and Smithen, C.E. 1964. The reactions of heterocyclic compounds with carbenes. Advances in Heterocyclic Chemistry, 3 57-78. 

Reactions of Heterocyclic Compounds with Carbenes 82KGS723... 

Rees, C. W., Smithen, C. E., The Reactions of Heterocyclic Compounds with Carbenes, 3,57. Reid, S. T., The Photochemistry of Heterocycles, 11,1 The Photochemistry of Oxygen- and Sulfur-Containing Heterocycles, 33, 1 Photochemistry of Nitrogert-Containing Heterocycles, 30, 239. 

New heterocyclization reactions with Fischer carbene complexes 06ARK (7)129. 

Other reactions of sulphonium ylides include o /9 -elimination,metal-mediated carbene-transfer to olefins, insertion into aromatic C—H bonds or other carbenoid-type processes, formation of Pd" complexes, addition to enones (forming cyclopropyl ketones or heterocycles ), reaction with isoquinoline 2-oxide, and [2,3]-sigmatropic rearrangements " [as in the case of (12) 1 or... 

Rees, C. W., Snuflien, C. E., The Reactions tf Heterocyclic Corrtpounds with Carbenes, 3,57. 

Very few reactions of carbenes with heterocyclic systems containing more than one hetero atom have been studied. They are confined to variants of the Reimer-Tiemann formylation of thiazoles, pyra-zoles, iminazoles, and indolizines/ and ring expansion does not appear to have been observed. 

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