The preparation of various 1-acyl-1,2-dihydropyridines with high regioselectivity by indium-mediated allylation of the corresponding 1-acylpyridinium salts is demonstrated. This is applied to the synthesis of (±)-dihydropinidines.
Efficient Solution-Phase Parallel Synthesis of 4-SubstitutedN-Protected Piperidines
作者:Xiaoyang Wang、Anna M. Kauppi、Roger Olsson、Fredrik Almqvist
DOI:10.1002/ejoc.200300387
日期:2003.12
Practical conditions for the synthesis of 4-substituted N-protected piperidines through CuCN·2LiBr-catalyzed organozinc additions to 1-acylpyridinium salts and subsequent hydrogen-transfer hydrogen ...
α-metalation of -(-butoxycarbonyl)-1,4-dihydropyridines
作者:Daniel L. Comins
DOI:10.1016/s0040-4039(00)88029-6
日期:1983.1
The α-metalation-alkylation of 4-substituted 1-(tert-butoxycarbonyl)-1,4-dihydropyridines is described. Subsequent aromatization provides a new route to 2,4-disubstituted pryidines.
Kinetics and Mechanism of the Pyridinolysis of Phenyl Chloroformates in Acetonitrile
作者:Han Joong Koh、Kwang Lae Han、Hai Whang Lee、Ikchoon Lee
DOI:10.1021/jo9814905
日期:1998.12.1
Kinetic studies on the reactions of Y-phenyl chloroformates with X-pyridines in acetonitrile are carried out at 25.0 degrees C. Both the Hammett and Bronsted plots are linear with enhanced substituent constants, sigma(p)(-), and basicities, pK(a)(-), for strong para pi-acceptor X-substituents, p-CN and p-CH3CO. This indicates that the electron-rich formate (O-C-O) moiety overlaps with the pyridine ring pi-system enabling, through conjugation with the para pi-acceptors, the rate-limiting formation of a tetrahedral intermediate. The difference in the aminolysis mechanism between methyl, II, and phenyl chloroformate, III, is attributed to the much stronger electron-donating polarizability effect of C6H5, than of CH3. The proposed mechanism is supported by a relatively small beta(X) (congruent to 0.3) and by the lower Delta H double dagger (6.7 kcal mol(-1)) and Delta S double dagger (-44 eu) values for a stronger donor Y (Y = p-CH3O) coupled with a stronger para pi-acceptor (X = p-CN) in pyridine.