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Chapter 3
Synthesis of trisubstituted pyrazoles/isoxazoles
Kewei Wang et al. 32 has reported an efficient and divergent one-pot synthesis
of fully substituted 1H-pyrazoles and isoxazole derivatives. Substituted 1H-pyrazoles
were synthesized from 1-carbamoyl, 1-oximyl cyclopropanes via sequential ringopening,
chlorovinylation, and intramolecular aza-cyclization under Vilsmeier
conditions (POCl 3 /DMF). Isoxazoles were synthesized from the cyclopropyl oximes
via ring-opening and intramolecular nucleophilic vinylic substitution (S N V) reactions
in the presence of POCl 3 /CH 2 Cl 2 (Figure-15).
Figure-15
Ebraheem Abdu Musad et al. 33 has prepared a new 3,5-(substituted) pyrazoles
and isoxazoles by reaction of (N’¹E , N’³E)- N’¹, N’³-bis(3,4,5-substitutedbenzylidene)malonohydrazide
with hydrazine hydrate and hydroxylamine
hydrochloride respectively under solvothermal conditions involving an ecofriendly
method without any environmental pollution (Figure-16).
Figure-16
Ch brajakishor singh et al. 34 have been synthesized a steroidal pyrazole and
isoxazole derivatives form 2-ethoxymethelene-4-androsten-3-one and 2-
bis(methylthio)methelene-4-androsten-3-one (Figure-17).
Figure-17
Department of Chemistry Saurashtra university, Rajkot-360005 90