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Synthesis of 1‐acyl‐1,2‐dihydro‐3 H ‐pyrazol‐3‐ones VIA lewis acid‐mediated rearrangement of 3‐acyloxypyrazoles
Author(s) -
Maruoka Hiroshi,
Yamagata Kenji,
Okabe Fumi,
Tomioka Yukihiko
Publication year - 2006
Publication title -
journal of heterocyclic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.321
H-Index - 59
eISSN - 1943-5193
pISSN - 0022-152X
DOI - 10.1002/jhet.5570430408
Subject(s) - chemistry , triethylamine , acylation , tin , chloride , lewis acids and bases , fries rearrangement , acyl chloride , medicinal chemistry , acyl group , acetyl chloride , organic chemistry , catalysis , alkyl
The unusual formation of 1‐acyl‐1,2‐dihydro‐3 H ‐pyrazol‐3‐ones starting from 3‐acyloxypyrazoles by Fries‐type rearrangement is described. Under normal conditions, acylation of 2,4‐dihydro‐3 H ‐pyrazol‐3‐ones 1 and 2 with acid chlorides or anhydrides in the presence of triethylamine gave the corresponding 3‐acyloxypyrazoles 3a‐f and 4a‐f . Treatment of 3a‐c and 4a‐f with Lewis acid, e.g. titanium(IV) chloride and tin(IV) chloride, caused migration of acyl groups to afford the corresponding 1‐acyl‐1,2‐dihydro‐3 H ‐pyrazol‐3‐ones 5a‐c and 6a‐f . Interestingly, the reactions of 3‐acyloxypyrazoles 3e and 3f with tin(IV) chloride provided the corresponding tin(IV) complexes 8e and 8f .