@article{MTMT:1013527,
	title = {Substituent-dependent negative hyperconjugation in 2-aryl-1,3-N,N-heterocycles. Fine-tuned anomeric effect?},
	url = {https://m2.mtmt.hu/api/publication/1013527},
	author = {Hetényi, Anasztázia and Martinek, Tamás and Lázár, László and Zalán, Zita and Fülöp, Ferenc},
	doi = {10.1021/jo034417},
	journal-iso = {J ORG CHEM},
	journal = {JOURNAL OF ORGANIC CHEMISTRY},
	volume = {68},
	unique-id = {1013527},
	issn = {0022-3263},
	abstract = {The epimerization reactions of conformationally inflexible 2-aryl-1,3-N,N-heterocycles were used as model systems to study the role of the nitrogen lone pair-C2 associated antibonding orbital hyperconjugative interactions in the experimentally observed substituent-dependent generalized anomeric effect. The measured reaction free enthalpies were found to correlate well with the sum of the hyperconjugative stabilization energies of all the vicinal donor-acceptor orbital overlaps around C2, obtained from ab initio NBO analysis, and both quantities correlated linearly with the Hammett-Brown substituent constant. The individual stereoelectronic interactions (n(N)-sigma*(C2-N), n(N)-sigma*(C2-Ar), n(N-sigma)*(C2-H)) were also observed to exhibit a substituent dependence, despite their distance from the 2-aryl substituent and their nonperiplanar arrangement. The higher the electron-withdrawing effect of the 2-aryl substituent, the larger was the stabilization for n(N)-sigma*(C2-Ar), while the overlaps n(N)-sigma*(C2-N) and n(N)-sigma*(C2-H) changed in the opposite sense. The different polarization of the acceptor sigma* orbitals, caused by the 2-aryl substituent, accounted for the observed propagation of the substituent effect. These results promote a detailed explanation of the useful tautomeric behavior of the 2-aryl-1,3-X,N-heterocycles, and reveal the nature of the connection between the anomeric effect and the Hammett-type linear free energy relationship.},
	year = {2003},
	eissn = {1520-6904},
	pages = {5705-5712},
	orcid-numbers = {Hetényi, Anasztázia/0000-0001-8080-6992; Martinek, Tamás/0000-0003-3168-8066; Lázár, László/0000-0002-2135-8496; Zalán, Zita/0000-0002-7146-3024; Fülöp, Ferenc/0000-0003-1066-5287}
}