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Solvent‐ and Transition Metal Catalyst‐Dependent Regioselectivity in the [3+2] Cyclocondensation of Trifluoromethyl ‐ α,β ‐ ynones with Hydrazines: Switchable Access to 3‐ and 5‐Trifluoromethylpyrazoles
Author(s) -
Hsieh MinTsang,
Kuo ShengChu,
Lin HuiChang
Publication year - 2015
Publication title -
advanced synthesis and catalysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.541
H-Index - 155
eISSN - 1615-4169
pISSN - 1615-4150
DOI - 10.1002/adsc.201400853
Subject(s) - regioselectivity , chemistry , trifluoromethyl , catalysis , yield (engineering) , transition metal , organic chemistry , medicinal chemistry , sulfoxide , alkyl , materials science , metallurgy
The regioselectivity of the [3+2] cyclocondensation of trifluoromethyl ‐ α,β ‐ ynones with hydrazines can be readily tuned to preferentially afford either 3‐ or 5‐trifluoromethylpyrazoles through variation of the reaction conditions. Under catalysis with copper(II) acetate (2.0 mol%), cyclocondensation proceeded smoothly to yield 3‐trifluoromethylpyrazoles with high regioselectivity. In contrast, when the reaction was conducted in dimethyl sulfoxide under catalyst‐free conditions, the formation of 5‐trifluoromethylpyrazoles was predominantly observed.