已经对3-取代的吡啶鎓盐的许多亲核开环进行了重新研究和总结。通过1 H NMR详细研究了所得稳定的戊二醛醛衍生物的结构。已经得出结论,通常亲核吡啶鎓开环是高度区域特异性的。迄今为止,在每种情况下,由于亲核试剂仅在一个吡啶α位上受到亲核试剂的攻击,都分离出了一种产物。OH离子是唯一的亲核试剂,攻击发生在吡啶C-2处,而较大的亲核试剂(例如胺和碳负离子)攻击发生在吡啶C-6处。对于多种3-取代的吡啶,例如3-甲基,3-甲氧基-,3-氰基-,3-氯吡啶,情况就是如此。
N.C.A. 11C-labelling of benzenoid compounds in ring positions: synthesis of 3-nitro-[3-11C]toluene and 4-nitro-[4-11C]toluene and their corresponding toluidines
A stereocontrolled alkylation of chiral pyridinium salts with Grignard reagents: synthesis of (+)-normetazocine and (+)-nordextrorphan
作者:Yves Genisson、Christian Marazano、Bhupesh C. Das
DOI:10.1021/jo00060a019
日期:1993.4
The synthesis of chiral pyridinium salts 3, bearing lipophilic counteranions, is described. These salts, soluble in THF or toluene, undergo nucleophilic alkylation with benzylic Grignard reagents to give, after reduction of the unstable dihydropyridine intermediates, adducts 4 with regio- and stereoselective attack at position 2, the observed stereoselectivity ranging from 8:1 to 12.5:1. These results allowed an asymmetric synthesis, following Grewe's route, of (+)-normetazocine and (+)-nordextrorphan, key precursors of various benzomorphan or morphinan drugs.
BECHER, J.;FINSEN, L.;WINCKELMANN, IB, TETRAHEDRON, 1981, 37, N 13, 2375-2378