3999-78-8Relevant articles and documents
Novel Synthesis of 3,5-Disubstituted Pyridines by 1,4-Cycloaddition of 1-Aza-1,3-butadienes with Enamines
Komatsu, Mitsuo,Takamatsu, Shigeki,Uesaka, Masatoshi,Yamamoto, Shinji,Ohshiro, Yoshiki,Agawa, Toshio
, p. 2691 - 2699 (2007/10/02)
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.
Catalytic reactions of pyridines. VI. Heterogeneous vapor-phase ring alkylation of pyridines with alcohols over H+-, Li+-, and alkaline earth cation-exchanged zeolites
Kashiwagi,Fujiki,Enomoto
, p. 2575 - 2578 (2007/10/02)
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