Universität zu Köln

Sheehy, Kevin J., Bateman, Lorraine M., Flosbach, Niko T., Breugst, Martin ORCID: 0000-0003-0950-8858 and Byrne, Peter A. (2020). Identification of N- or O-Alkylation of Aromatic Nitrogen Heterocycles and N-Oxides Using H-1-N-15 HMBC NMR Spectroscopy. Eur. J. Org. Chem., 2020 (22). S. 3270 - 3282. WEINHEIM: WILEY-V C H VERLAG GMBH. ISSN 1099-0690

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Abstract

A series of representative diazines and pyridine N-oxides were subjected to alkylation using several different alkylating agents. The N-15 NMR chemical shifts (delta(N) values) of the diazines, pyridine N-oxides and derived alkylation products were determined using H-1-N-15 HMBC NMR spectroscopy at natural N-15 abundance. The changes in the N-15 NMR chemical shifts (Delta(delta(N)) values) that occurred on going from starting materials to products in these reactions were analyzed. N-alkylation of diazines resulted in large upfield shifts of the delta(N) values of the alkylated nitrogen (of the order of 100 ppm or greater). While O-alkylation of pyridine N-oxides resulted in upfield shifts of the delta(N) values of the N-(alkoxy)pyridinium nitrogen, the Delta(delta(N)) values were of a much smaller magnitude (ca. -42 ppm) than those observed for N-alkylations of diazines. Nitrogen NMR spectroscopic data from the literature of relevance to alkylation of azines, diazines, azine N-oxides and diazine N-oxides was gathered together, and using this in tandem with our N-15 NMR spectroscopic data, we have been able to corroborate our observations on the trends observed in the Delta(delta(N)) values associated with N- and O-alkylation reactions of aromatic N-heterocycles and N-oxides. An analysis protocol that relies on synergistic evaluation of H-1-N-15 HMBC and H-1-C-13 HMBC NMR spectra has been developed that enables unambiguous diagnosis of the occurrence of N-alkylation of aromatic N-heterocycles and O-alkylation of aromatic N-oxides.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Sheehy, Kevin J. UNSPECIFIED UNSPECIFIED UNSPECIFIED Bateman, Lorraine M. UNSPECIFIED UNSPECIFIED UNSPECIFIED Flosbach, Niko T. UNSPECIFIED UNSPECIFIED UNSPECIFIED Breugst, Martin UNSPECIFIED orcid.org/0000-0003-0950-8858 UNSPECIFIED Byrne, Peter A. UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-332812
DOI:	10.1002/ejoc.202000329
Journal or Publication Title:	Eur. J. Org. Chem.
Volume:	2020
Number:	22
Page Range:	S. 3270 - 3282
Date:	2020
Publisher:	WILEY-V C H VERLAG GMBH
Place of Publication:	WEINHEIM
ISSN:	1099-0690
Language:	English
Faculty:	Faculty of Mathematics and Natural Sciences
Divisions:	Faculty of Mathematics and Natural Sciences > Department of Chemistry > Institute of Organic Chemistry
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language NUCLEAR-MAGNETIC-RESONANCE; N-15 NMR; CHEMICAL-SHIFTS; ALKOXYPYRIDINIUM SALTS; COORDINATION SHIFTS; PROTON-TRANSFER; PYRIDINE; C-13; H-1; COMPLEXES Multiple languages Chemistry, Organic Multiple languages
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/33281