Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Diazo compounds pyrazolenines

Pyrazoles are formed when the diazo compounds react with alkynes or with functionalized alkenes, viz. the enols of /3-diketones. Pyrazolenines (353 Section 4.04.2.2.1) are isolated from disubstituted diazomethanes. Many pyrazoles, difficult to obtain by other methods, have been prepared by this procedure, for example 3-cyanopyrazole (616) is obtained from cyanoacetylene and diazomethane (7iJCS(C)2i47), 3,4,5-tris(trifiuoromethyl)pyrazole (617) from trifluorodiazoethane and hexafluoro-2-butyne (8lAHC(28)l), and 4-phenyl-3-triflylpyrazole (618 R =H) from phenyltriflylacetylene and diazomethane (82MI40402). An excess of diazomethane causes iV-methylation of the pyrazole (618 R = H) and the two isomers (618 R = Me) and (619) are formed in a ratio of 1 1. [Pg.282]

The formation of pyrazolenines demands, as in the cyclopropenone series, the intermediacy of conjugated diazo compounds, e.g. 549, arising from valence tautomeriza-tion of diaza bicyclo(3,l,0)hexanes, e.g. 548. [Pg.108]


See other pages where Diazo compounds pyrazolenines is mentioned: [Pg.382]    [Pg.138]   
See also in sourсe #XX -- [ Pg.20 ]




SEARCH



Diazo compounds

Pyrazolenines

© 2024 chempedia.info