Determination of substitution sites in monosubstituted five-membered aromatic heterocycles

Similar magnitudes of proton–proton couplings across three, four, and five bonds and proton–carbon couplings across two and three bonds combined with difficult to predict substituent effects make the results of an indiscriminate use of routine (COSY, HSQC, HMBC, etc.) techniques for substitution sit...

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Bibliographic Details
Published in:Magnetic resonance in chemistry 2011-03, Vol.49 (3), p.147-150
Main Authors: Schraml, Jan, Kubec, Roman, Kučerová, Petra
Format: Article
Language:English
Subjects:
1,1‐ADEQUATE
1-ADEQUATE
13C NMR
1H NMR
Couplings
INADEQUATE
Inclusions
Magnetic resonance
Natural products
pyrrole
Routines
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Summary:Similar magnitudes of proton–proton couplings across three, four, and five bonds and proton–carbon couplings across two and three bonds combined with difficult to predict substituent effects make the results of an indiscriminate use of routine (COSY, HSQC, HMBC, etc.) techniques for substitution site determination in C‐monosubstituted five‐membered heteroaromatics suspect. As demonstrated on two examples of natural products, the use of 1,1‐ADEQUATE leads to unambiguous substitution site determination lending thus further support to suggested inclusion of 1,1‐ADEQUATE data into computer‐assisted structure elucidation (CASE) protocols. Copyright © 2011 John Wiley & Sons, Ltd. 1,1‐ADEQUATE provides a fool‐proof method for the determination of the substitution site in monosubstituted five‐memebered aromatic heterocycles where routine methods are likely to fail because of similar magnitudes of proton–proton couplings across three, four, and five bonds and proton–carbon couplings across two and three bonds.
ISSN:0749-1581
1097-458X
1097-458X
DOI:10.1002/mrc.2725