Michael addition on double and triple bonds

The reaction of A -substituted pyrazoles with alkynic esters in the presence of fluoroboric acid yields Michael addition salts and not Diels-Alder adducts as was previously reported in the literature 83T2193 . Addition of 3,5-dimethyl-pyrazole to DMAD (dimethyl acetylenedicarboxylate) is highly stereoselective in aprotic solvents, yielding mono- and bis-adducts 85JCS(P2)427 . 

Michael addition of azoles on acrylamide affords A-azolylpropanamides 88JHC225 . In this way derivatives of pyrazole (7), indazole, 5-chloroindazole, and 5-nitroindazole have been prepared and characterized by H and C NMR spectroscopy. In the case of indazoles, both isomers are formed which isomerize to the most stable 1//-derivative with activation energies high enough to observe both isomers but not to prevent their equilibration. 

Some 1,1 -diindazolylphenylmethanes have been prepared from indazoles and benzaldehyde in presence of zinc chloride as catalyst 85T5955 . The reaction proceeds similarly with other azoles, like pyrazole, 4-bromopyrazole, and 3-methyl-4-bromopyrazole 88CPB2036 . When the resulting compound was chiral, for instance (111), its resolution was successfully carried out by hquid chromatography on triacetylcellulose 88H(27)35i . 

Addition of pyrazoles to quinones affords mono- (114) and bis- ortho (115) and para (116)) pyrazol-l-yl-hydroquinones, NMR and crystallography were used to identify these compounds 90JA747 . The mechanism of the formation of these products involves Michael additions (monoadducts) and oxidation by quinones (bis-adducts) 92JOC1873 . 

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