Cyclization of tautomeric 1,5-dinitrile systems with hydrogen halides: A definitive mechanistic rationalization?
A new mechanistic rationalization for the cyclization with hydrogen halides of tautomeric 1,5-dinitriles of general structures (10) (Z = N), (14) (Z = C-CN), (16) (Z = N), and (18) (Z = C-CN) is proposed (Scheme 5). In such rationalization, three factors
CYCLIZATION OF 2-DICYANOMETHYLENE-1,2-DIHYDROPYRIDINE-3-CARBONITRILES WITH HYDROGEN HALIDES: A RE-EXAMINATION ON THE REGIOSELECTIVITY
The cyclization of the title compounds (5a-c) with HCl and HBr has been re-examined.In all cases 5-amino-7-halo-substituted 1,6-naphthyridines (11a-c and 12a-c) were formed independently of the thermal level and the hydrogen halide employed.The structures of 11a-c and 12a-c were unequivocally established by reaction with hydrazine which affforded the corresponding pyrazolonaphthyridines (14a-c).The structure of the methoxy derivatives (15a,c and 16a,c) was assigned by two-dimensional nmr studies.
Victory, Pedro,Busquets, Nuria,Borrell, Jose I.,Teixido, Jordi,Serra, Blanca,et al.
p. 1013 - 1022
(2007/10/02)
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