1-Acyl-4-benzylpyridinium Tetrafluoroborates: Stability, Structural Properties, and Utilization for the Synthesis of Acyl Fluorides

✍ Scribed by Rüdiger Wagner; Bernd Wiedel; Wolfgang Günther; Helmar Görls; Ernst Anders

• Publisher: John Wiley and Sons
• Year: 1999
• Tongue: English
• Weight: 226 KB
• Volume: 1999
• Category: Article
• ISSN: 1434-193X
• DOI: 10.1002/(sici)1099-0690(199909)1999:9<2383::aid-ejoc2383>3.0.co;2-t

✦ Synopsis

Acyl-4-benzylpyridinium salts 4 containing nonnucleo-by the pyridine moiety of 4, which splits off and functions as a Lewis base to intercept the BF 3 acid. The structural and philic anions X -such as CF 3 SO 3 -, FSO 3 -, and BF 4 -can be generated quantitatively and in situ from 1-acyl-4-electronic relationships as well as dominating differences between the very reactive cations of 4 and their almost alkylidene-1,4-dihydropyridines 1a-f and the corresponding acid, HX. The BF 4 -salts reveal an interesting and "inert" uncharged precursors, the dihydropyridines 1, are discussed both on the fundament of experimental evidence unexpected thermal instability which allows the convenient synthesis of carboxylic acid fluorides 5b-f. This procedure (X-ray structures of 1f and the extremely reactive and very labile 4f) and theoretical investigations (ab initio and DFT offers advantages over known methods: All operations can be performed in a standard glass apparatus and do not MO calculations). require high pressures. The formation of RCOF 5 is assisted