Synthesis 2005(9): 1425-1430  
DOI: 10.1055/s-2005-865317
PAPER
© Georg Thieme Verlag Stuttgart · New York

The Stability of Acylpyridinium Cations and Their Relation to the Catalytic Activity of Pyridine Bases

I. Held, A. Villinger, H. Zipse*
Department Chemie und Biochemie, LMU München, Butenandtstrasse 13, 81377 München, Germany
Fax: +49(89)218077738; e-Mail: zipse@cup.uni-muenchen.de;
Further Information

Publication History

Received 28 February 2005
Publication Date:
13 April 2005 (online)

Abstract

The stability of acylpyridinium cations can be used as a predictive tool for the development of catalysts for acyl transfer reactions based on the 4-aminopyridine motive. Substituents in 2-position of the pyridine ring are detrimental to both, the catalytic activity of pyridine catalysts as well as the stability of the respective acetylpyridinium cations. Alkyl substituents located in 3-position of the pyridine ring and at the nitrogen substituent in 4-position lead to higher catalytic activity as well as more stable acetylpyridinium cations. This is, of course, only true as long as steric effects do not hinder the proper alignment of the 4-amino substituent and the pyridine ring.

18

Bräse, S. private communication.