Diazo-compounds aliphatic, pyrazoles from

Pyrazoles, synthesis from aliphatic diazo compounds 78KGS579. Pyrazoles, synthesis from hydrazines 84H(22) 1821. 

C. Synthesis of Pyrazoles from Aliphatic Diazo Compounds 381... 

Cases are known where pyrazoles are formed from aliphatic diazo compounds and cyano-olefins,462,493 or nitro-olefins, the latter reaction being studied systematically by Parham and co-workers, who established that the relatively stable nitropyrazolines initially formed eliminate nitrous acid when heated with acid.484-486 (See also reference 486a.) When the diazo compound is gem-disubstituted, a pyrazole is formed by migration of one of the groups, which was... 

Pyrazolines may be obtained readily from a,j3-unsaturated aldehydes or ketones and aliphatic diazo compounds.44,349 Convenient syntheses have been worked out using Mannich bases,488-494 by the cyclization of aldehydo- and keto-azines.495-499 The conversion of a number of 4- and 5-substituted pyrazolines to the corresponding pyrazoles by frams-elimination was noted above. The 4-amino-pyrazolines with the appropriate configuration (41) readily eliminate... 

Very active interest in a new addition reaction of aliphatic diazo compounds started in 1991 when WudPs group reported that diphenyldiazomethane forms diphenylmethanofullerene with buckminsterfullerene (C o Suzuki et al., 1991). Although this investigation showed that the reaction proceeds via the formation of a dihydro-pyrazole, i.e., in the mode of a 1,3-dipolar cycloaddition followed by an azo-extrusion, we shall discuss the syntheses of methanofullerenes in its entirety in the chapter on carbenes (Sect. 8.4) because Diederich s recent work (see review of Diederich et al., 1994b) shows that the methano bridge can also be obtained from a carbene. The question whether the dihydro-pyrazoles are intermediates or side-equilibrium products (see earlier in this section) is also open for the reaction of with diazoalkanes. 

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