Enantioenrichment of a tungsten dearomatization agent utilizing chiral acids

Andrew W Lankenau; Diana A Iovan; Jared A Pienkos; Rebecca J Salomon; Sisi Wang; Daniel P Harrison; William H Myers; W Dean Harman

doi:10.1021/jacs.5b00490

Enantioenrichment of a tungsten dearomatization agent utilizing chiral acids

J Am Chem Soc. 2015 Mar 18;137(10):3649-55. doi: 10.1021/jacs.5b00490. Epub 2015 Mar 6.

Authors

Andrew W Lankenau¹, Diana A Iovan², Jared A Pienkos¹, Rebecca J Salomon¹, Sisi Wang¹, Daniel P Harrison¹, William H Myers², W Dean Harman¹

Affiliations

¹ †Department of Chemistry, University of Virginia, Charlottesville, Virginia 22904, United States.
² ‡Department of Chemistry, University of Richmond, Richmond, Virginia 23173, United States.

PMID: 25710752
DOI: 10.1021/jacs.5b00490

Abstract

A method is described for the resolution of the versatile dearomatization reagent TpW(NO)(PMe3)(η(2)-benzene), in which the 1,3-dimethoxybenzene (DMB) analogue of this complex is synthesized. In turn, the coordinated arene of TpW(NO)(PMe3)(DMB) is protonated with either D or L dibenzoyl tartaric acid (DBTH2) in a butanone/water or 2-pentanone/water solution. Sustained stirring of this mixture results in the selective precipitation of a single form of the diastereomeric salt [TpW(NO)(PMe3)(DMBH)](DBTH). After isolation, the salt can be redissolved, and the DMB ligand can be deprotonated and exchanged for benzene to produce the desired product TpW(NO)(PMe3)(η(2)-benzene) in either its R or S form. The absolute configuration of the tungsten stereocenter in TpW(NO)(PMe3)(η(2)-benzene) can be determined in either case by substituting the naturally occurring terpene (S)-β-pinene for benzene and evaluating the 2D NMR spectrum of the corresponding β-pinene complex.