Preparation of 5-acyl- and 5-aryl-substituted 1-(benzyloxy)pyrazoles via directed ortho-lithiation/transmetalation and palladium catalyzed cross- coupling
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Palladium(0) catalyzed cross-coupling of 1-(benzyloxy)pyrazol-5-ylzinc halides 3a,b, prepared by transmetalation of 1-(benzyloxy)-5-lithiopyrazole (2), with acyl chlorides produced 5 acyl-1-(benzyloxy)pyrazoles 4a-d in high yields. Similar coupling of the pyrazol-5-ylzinc halide with amino-, hydroxy- , methoxy-, fluoro-, nitro-, or formyl-substituted iodobenzene gave the corresponding 5-aryl-1-(benzyloxy)pyrazoles 5a-f, while coupling with iodothiophene, iodopyrazole or bromopyridine provided the corresponding 1- (benzyloxy)-5-heteroarylpyrazoles 6a-c.
|Number of pages||5|
|Publication status||Published - 1 Nov 1998|