J. CHEM. RESEARCH (S), 1999 715
In conclusion, the present results demonstrate the novelty
of zinc^nickel chloride hexahydrate^THF combination sys-
tem which shows unique selectivity and constitutes a useful
alternative to the commonly accepted procedure for the syn-
thesis of various arylhydrazines. Moreover, this simple and
easily reducible technique a¡ords products in excellent
yields without involvement of expensive materials and
without formation of any undesirable side-products of
the classical methods.
Received, 12th July 1999; Accepted, 27th August 1999
Paper E/9/05588F
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Experimental
All chemicals were of analytical grade. The solvents were freshly
distilled before use. Commercially available zinc powder and nickel
chloride hexahydrate were used as received. All aryldiazonium
£uoroborates were prepared by using standard synthetic methods.8
General Procedure for Chemoselective Reduction of Substituted
Aryldiazonium Fluoroborates.öA mixture of zinc powder (2 mmol)
and nickel chloride hexahydrate (3 mmol) and aryldiazonium
£uoroborate (2 mmol) in tetrahydrofuran (10 ml) at 0 8C was stirred.
A vigorous exothermic reaction takes place immediately which is
controlled by keeping the reaction mixture in an ice-bath. After
completion of the reaction, THF was removed under vacuum and the
product was extracted with diethyl ether (3 Â 10 ml). The ether layer
was dried with anhydrous sodium sulfate and removal of the solvent
under reduced pressure affords the arylhydrazine in almost pure
form; further puri®cation, if required, can be performed by
chromatography.
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8