Transformation of Zwitterionic Pyridine Derivatives to a Spiro-Fused Ring System: Azoniabenzo[de]fluorine. Synthesis and Mechanistic Rationalization
摘要:
Reaction of aryl- and benzylsulfanopyridinium amidates bearing a methyl group in position 6 with 2 equiv of diphenylketene afforded a spiro-fused ring system: azoniabenzo[de]fluorine. By use of an excess amount of ketene, a distinct reaction was observed via which a 1H-pyrrolo[3,2-b]pyridin-2(3H)-one derivative was furnished. The structure of the tetracyclic spiro-fused ring system was unambiguously confirmed by X-ray diffraction, and its formation was rationalized by DFT calculations.
Rearrangement of Aryl- and Benzylthiopyridinium Imides with Participation of a Methyl Substituent
作者:Roberta Palkó、Orsolya Egyed、Zsuzsanna Riedl、Tibor András Rokob、György Hajós
DOI:10.1021/jo201645t
日期:2011.11.18
substituted 2-aryl- and 2-benzylthiopyridinium N-imides reacted with an excess of isocyanates to give N,N-disubstituted exocyclic1H-imidazo[4,5-b]pyridin-2(3H)-ones. The products easily underwent spontaneous [1,5] hydrogen shift to provide the heteroaromatic imidazopyridinone isomers. The transformation implied the initial formation of [1,2,4]triazolo[2,3-a]pyridinium salt, followed by deprotonation and
6-甲基取代的2-芳基-和2-苄基硫代吡啶鎓N-酰亚胺与过量的异氰酸酯反应,得到N,N-二取代的环外环1 H-咪唑并[4,5 - b ]吡啶-2-2 (3 H)-。产物容易发生自发的[1,5]氢转移,以提供杂芳族咪唑并吡啶酮酮异构体。该转化表明[1,2,4]三唑[2,3- a ]的初始形成吡啶鎓盐,然后进行亚甲基部分的去质子化和氨基甲酰化,最后按照[1,3]σ型进行重排。机理上的考虑表明,一些实验发现揭示了环转化步骤的非一致的两步机理。