- Cross Mannich Reaction of Aldehydes; Efficient Synthesis of Substituted Pyridines
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Symmetrically and unsymmetrically substituted pyridines were obtained in highly efficient one-pot procedures starting from α-unbranched aldehydes and iminium salts.
- Winter, Andreas,Risch, Nikolaus
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p. 2667 - 2670
(2007/10/03)
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- Novel Synthesis of 3,5-Disubstituted Pyridines by 1,4-Cycloaddition of 1-Aza-1,3-butadienes with Enamines
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A new method for the synthesis of 3,5-disubstituted pyridines is described.Reactions of the N-substituted methanimines 1 with the β-substituted enamines 2 give 1-aza-1,3-butadienes 3a-3i and/or symmetrically 3,5-disubstituted pyridines 4a-c,e-h in moderate to good yields.At reaction temperatures of 150 deg C the azadienes 3 are the predominant products, and the reaction provides a good route to 1-azadienes with no substituent at the 4-position.At reaction temperatures of 200 deg C, and particularly using N-tert-butylmethanimine 1a and p-toluenesulfonic acid catalyst, the principal products are symmetrically 3,5-disubstituted pyridines.The cycloaddition was shown to proceed via the azabutadiene intermediate 3.Reactions of 3 with the enamines 2 lead to unsymmetrically 3,5-disubstituted pyridines.The mechanisms of these cycloadditions are discussed.
- Komatsu, Mitsuo,Takamatsu, Shigeki,Uesaka, Masatoshi,Yamamoto, Shinji,Ohshiro, Yoshiki,Agawa, Toshio
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p. 2691 - 2699
(2007/10/02)
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- SYNTHESIS OF ALKYL-SUBSTITUTED ARYLPYRIDINES IN THE VAPOR PHASE BY THE CHICHIBABIN METHOD
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An industrial cadmium calcium phosphate catalyst was used in the syntheses of pyridine bases in the vapor phase by the Chichibabin method (condensation of carbonyl compounds with ammonia).Alkyl-substituted arylpyridines with the aryl radical at C2, C3, or C4 are formed during the condensation of aromatic aldehydes and ammonia with saturated and unsaturated aldehydes and also with methyl alkyl ketones.
- Soldatenkov, A. T.,Fedorov, V. O.,Chandra, R.,Polosin, V. M.,Mikaya, A. I.,Prostakov, N. S.
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p. 179 - 185
(2007/10/02)
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