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A practical approach for spiro‐ and 5‐monoalkylated barbituric acids
Author(s) -
Singh Palwinder,
Paul Kamaldeep
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.5570430313
Subject(s) - chemistry , alkylation , barbituric acid , catalysis , octane , medicinal chemistry , alkyl , base (topology) , phase (matter) , ring (chemistry) , organic chemistry , mathematical analysis , mathematics
The single step reactions of N,N′‐ substituted/‐unsubstituted barbituric acids with various alkyl dihalides under phase transfer catalytic conditions using DMF‐K 2 CO 3 (base), TBAHSO 4 (catalyst) provide spirobarbituric acids in moderate to high yields. Irrespective of the existence of C 5 ‐monoalkylated compounds in the enolic form (confirmed by the isolation of some of its analogues), the second alkylation predominantly takes place at C 5 . The underlying mechanism for the reaction is discussed. The 5,7‐dimethyl‐5,7‐diaza‐spiro[2.5]octane‐4,6,8‐trione undergoes ring opening with NaCN, PhSH, HS(CH 2 ) 2 OH and Br 2 to provide 5‐monoalkylated barbiturates which are otherwise difficult to prepare by the usual alkylation of barbituric acids.