Synthetic applications of N-N linked heterocycles. Part 8. Regiospecific synthesis of 4-(α-acylalkyl)pyridines by attack of lithium enolates of ketones γ to N-(2,6-dimethyl-4-oxopyridin-1-yl)pyridinium salts
作者:Cheuk Man Lee、Michael P. Sammes、Alan R. Katritzky
DOI:10.1039/p19800002458
日期:——
salts (2)–(4) to lithium enolates (1) of ketones in tetrahydrofuran at low temperatures gives regiospecifically high yields of 1,4-dihydro-adducts (5)–(7). These are readily isolated and can be decomposed under free-radical conditions, also in high yield, to 4-(α-acylalkyl)pyridines (8)–(10). Unsymmetrical dialkyl ketones give a mixture of two isomeric products, the ratio depending upon reaction conditions
的添加ñ - (2,6-二甲基-4-氧代吡啶-1-基)吡啶鎓盐(2) - (4)至烯醇化物锂(1酮)在四氢呋喃中,在低温下给出的1,4-区域专一性高的产率-二氢加合物(5)–(7)。它们很容易分离,并且可以在自由基条件下以高收率分解为4-(α-酰基烷基)吡啶(8)–(10)。不对称的二烷基酮产生两种异构产物的混合物,其比例取决于反应条件和空间因素。然而,αβ-不饱和酮仅在羰基的α'位置产生反应产生的产物。