ISSN:
1434-193X
Keywords:
4-Alkylidene-1,4-dihydropyridines
;
1-Acyl-4-benzylpyridinium tetrafluoroborates
;
Carboxylic acid fluorides
;
X-ray structures
;
Ab initio calculations
;
Density functional calculations
;
Chemistry
;
General Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
1-Acyl-4-benzylpyridinium salts 4 containing nonnucleophilic anions X- such as CF3SO3-, FSO3-, and BF4- can be generated quantitatively and in situ from 1-acyl-4-alkylidene-1,4-dihydropyridines 1a-f and the corresponding acid, HX. The BF4- salts reveal an interesting and unexpected thermal instability which allows the convenient synthesis of carboxylic acid fluorides 5b-f. This procedure offers advantages over known methods: All operations can be performed in a standard glass apparatus and do not require high pressures. The formation of RCOF 5 is assisted by the pyridine moiety of 4, which splits off and functions as a Lewis base to intercept the BF3 acid. The structural and electronic relationships as well as dominating differences between the very reactive cations of 4 and their almost “inert” uncharged precursors, the dihydropyridines 1, are discussed both on the fundament of experimental evidence (X-ray structures of 1f and the extremely reactive and very labile 4f) and theoretical investigations (ab initio and DFT MO calculations).
Additional Material:
2 Ill.
Type of Medium:
Electronic Resource
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