ISSN:
0009-2940
Keywords:
Ketene N,X1-acetals, cyclic
;
Azolium salts, 2-alkyl-deprotonation of
;
Imidazolidines, 2-alkylidene-
;
Benzimidazoles, 2-alkylidenedihydro-
;
Benzoxazoles, 2-alkylidenedihydro-
;
Oxazolidines, 2-alkylidene
;
Indoles, 2-alkylidenedihydro-
;
Perimidines, 2-alkylidenedihydro-
;
IGLO calculations
;
1,3-Dipolar cycloaddition reactivity and carbon-13 chemical shifts, correlation between
;
Photoelectron spectra
;
Electronic structures
;
Calculations, AM1, MNDO, PM3
;
Chemistry
;
Inorganic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
Synthesis, NMR Spectra, and Photoelectron Spectra of Cyclic Ketene N, X1-Acetals (2-Alkylidene-N-heterocycles)Deprotonation by sodium hydride of the N1-methyl-2-alkyl-azolium salts 10c, 14-16 and 18 and of the perimidinium salt 20 as well affords the corresponding ketene N,X1-acetals 1c, 3-5, 7, and 8 as air-sensitive distillable oils or low-melting crystals. The α1-carbon atoms of cyclic ketene N,X1-acetals resonate at very high field with the smallest chemical shift of no more than δ=39 for the 5-methylenedihydrotetrazol 2a. Geometries of 1a, b, 2a, and b were optimized on the Hartree-Fock level with polarized double-ζ basis sets, followed by IGLO calculations of the NMR chemical shifts. These are in excellent agreement with the unusual carbon-13 shifts observed. The electronic structures of 1a, b, 2a, b, 3a, b, 4b, 5b, 6a, and b are investigated by photoelectron spectroscopy and semi-empirical quantum chemical calculations. The observed ionization potentials are assigned to molecular orbitals on the basis of Koopmans' theorem. The order of reactivity in 1,3-dipolar cycloaddition reactions of cyclic ketene N,X1-acetals resembles that of the chemical shifts of their α1-carbon atoms.
Additional Material:
11 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/cber.19931260230
Permalink
