Models for incomplete nucleophilic attack on a protonated carbonyl group and electron-deficient alkenes: salts and zwitterions from 1-dimethylamino-naphthalene-8-carbaldehyde
作者:Alberth Lari、Matuesz B. Pitak、Simon J. Coles、Gregory J. Rees、Stephen P. Day、Mark E. Smith、John V. Hanna、John D. Wallis
DOI:10.1039/c2ob25929j
日期:——
The X-ray crystal structures of salts and zwitterionic Knoevenagel products from 1-dimethylamino-naphthalene-8-carbaldehyde show long N–C bonds between peri-groups which provide models for incomplete nucleophilic attack on a protonated carbonyl group and electron-deficient alkenes respectively. For the salts the N–C bonds lie in the range 1.625–1.638 Å with C–OH bonds intermediate in length between single and double bonds, while for the zwitterions the N–C bonds lie in the range 1.612–1.660 Å. The structural assignment of the former is supported by solid state 13C and 15N NMR studies on doubly isotopically-labelled material. Several zwitterions were converted to naphtha[1,8-bc]azepines by a mechanism involving the tertiary amino effect.
1-二甲氨基-萘-8-甲醛的盐和两性离子 Knoevenagel 产物的 X 射线晶体结构显示,周边基团之间存在长 N-C 键,这分别为质子化羰基和缺电子烯烃的不完全亲核攻击提供了模型。对于盐,N-C 键的范围为 1.625-1.638 Å,C-OH 键的长度介于单键和双键之间,而对于两性离子,N-C 键的范围为 1.612-1.660 Å。前者的结构归属得到了双同位素标记材料的固态 13C 和 15N NMR 研究的支持。一些两性离子通过涉及叔氨基效应的机制转化为石脑油[1,8-bc]氮杂卓类化合物。