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Chapter 3
Synthesis of trisubstituted pyrazoles/isoxazoles
Figure-21
Galal H. Elgemeie et al. 39 have been synthesized a variety of novel α-
cyanoketene S,S-acetals, readily prepared by the reaction of cyanoacetanilides or
cyanothioacetamide with carbon disulfide, followed by alkylation, react smoothly
with nucleophile to afford variously substituted methylthio derivatives of pyrazole
(Figure-22).
MeS
SMe
CN
RNHNH 2
H 2 N
S
EtOH, PiP, heat
NH 2
H 2 N
N
N
R
R= H, Ph
Figure-22
Jesse P. Waldo et al. 40 have been synthesized of isoxazoles (Figure-23) via
electrophilic cyclization under mild reaction conditions by the reaction of 2-alkyn-1-
one O-methyl oximes with ICl, I 2 , Br 2 , or PhSeBr.
O
SMe
Figure-23
David J. Burkhart et al. 41 have been synthesized ethyl 4-acetyl-5-methyl-3-
isoxazoyl carboxylate (Figure-24) was smoothly lithiated at the 5-methyl position.
The anion was quenched with a variety of electrophiles such as alkyl halides,
aldehyde, TMSCl and Me 3 SnCl in good to excellent yields.
Figure-24
Department of Chemistry Saurashtra university, Rajkot-360005 92