A. Schmidt et al., Modified uracils convertible between cations, conjugated, and cross-conjugated mesomeric betaines. Syntheses, semiempirical study, and X-ray analysis, HETEROCYCLE, 51(2), 1999, pp. 237-242
Nucleophilic substitution on the 6-chlorouracils (1) and (8) by heteroaroma
tics such as DMAP, 4-methylpyridine, and 3-hydroxypyridine yielded uracilyl
pyridinium salts (2, 3, 7, 10), mesomeric betaines (4, 5, 6), and a bis-bet
aine (9), respectively. A prototropic shift converts the CCMB (6A) into the
CMB (6B), the dipole moments and most stable conformations of which were c
alculated. X-Ray crystallography was performed on the uracilylpyridinium sa
lt (7).