Rhodium-catalysed reactions diazo compounds

The inclusion of a separate chapter on catalysed cyclopropanation in this latest volume of the series is indicative of the very high level of activity in the area of metal catalysed reactions of diazo compounds. Excellent, reproducible catalytic systems, based mainly on rhodium, copper or palladium, are now readily available for cyclopropanation of a wide variety of alkenes. Both intermolecular and intramolecular reactions have been explored extensively in the synthesis of novel cyclopropanes including natural products. Major advances have been made in both regiocontrol and stereocontrol, the latter leading to the growing use of chiral catalysts for producing enantiopure cyclopropane derivatives. 

Reaction with benzene follows a similar pathway, yielding a bicyclo[3.2.2]nonatriene structure. Vinylcarbenoids also react with pyrroles to give tropanes via a cyclopropanation-Cope rearrangement route. The direct addition of carbenes to acetylenes does not give satisfactory yields of cyclopropanes, but the rhodium carboxylate catalysed reaction of diazo compounds with acetylenes is a useful source of cyclopro-panes. Carbenoids can also attack a carbonyl oxygen atom, giving rise to a zwitterion (249). An excellent review of intramolecular carbenoid reactions has appeared. ... 

The 3 -I- 2-cycloaddition reactions of A-alkylsufonylimines with alkenes, enamines, ynamines, diazo compounds, azirines, silyloxydienes, and azadienes have been extensively reviewed. Rhodium(III)-catalysed cycloaddition of cyclic sulfonylketimines with internal alkynes afforded multifunctional spirocyclic sultam products in high... 

Collomb, D., Chantegrel, B., and Deshayas, C., Chemoselectivity in the rhodium(ll) acetate catalysed decomposition of a-diazo-P-keto-y.S-alkenyl-S-aryl compounds. Aromatic C-H insertion reaction or Wolff rearrangement-electrocyclization. Tetrahedron, 52, 10455, 1996. 

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