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Synthesis of [2‐(Trimethylsilyl)ethynyl]pyrazoles Based on Bis(trimethylsilyl)acetylene and Arylacetyl Chlorides
Author(s) -
Pankova Alena S.,
Golubev Pavel R.,
Ananyev Ivan V.,
Kuznetsov Mikhail A.
Publication year - 2012
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.201200807
Subject(s) - trimethylsilyl , chemistry , acetylene , hydrazine (antidepressant) , organic chemistry , trimethylsilyl azide , condensation , catalysis , physics , chromatography , thermodynamics
A practical approach to the synthesis of [2‐(trimethylsilyl)ethynyl]pyrazoles was developed through condensation of hydrazines with enynones that are easily accessible frombis(trimethylsilyl)acetylene and arylacetyl chlorides. Optimized conditions for reactions with monoarylhydrazines permit the chemoselective formation of 5‐alkynylpyrazoles in high yields (48–94 %). When monoalkylhydrazines or the parent hydrazine is used, mixtures of 3‐ and 5‐alkynylpyrazoles are formed in 73–79 % yields. The method uses inexpensive starting materials and can be applied to a variety of substrates, which makes it convenient for the synthesis of alkynylpyrazoles.