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Communication

Fomenting Proton Anisochronicity in the CH₂D Group

Benjamin D. Allen and Daniel J. O'Leary*

Department of Chemistry, Pomona College, 645 North College Avenue, Claremont, California 91711-6338

J. Am. Chem. Soc., 2003, 125 (30), pp 9018–9019

DOI: 10.1021/ja034242l

Publication Date (Web): July 2, 2003

In papers with more than one author, the asterisk indicates the name of the author to whom inquiries about the paper should be addressed.

doleary@pomona.edu

Abstract

A novel C−D···N interaction promotes an equilibrium isotope effect that causes a large chemical shift difference (43 ppb, 22 °C) for the diastereotopic methyl protons in the (N-CH₂D)-(−)-isosparteinium cation. The observed chemical shift difference is in surprising agreement with a prediction of 44 ppb based upon an ab initio protocol. These calculations are also shown to reproduce the experimental shift difference in Anet's α-deutero-1,2-dimethylpiperidine (theory, 17 ppb; experiment, 14 ppb). The isosparteine-derived system described herein may provide an improved method for assigning the configuration and enantiomeric purity of stereogenic methyl groups (R-CHDT) by tritium NMR spectroscopy.

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