Absolute Configuration Determination of Azulenyl Diols Isolated From Asymmetric Pinacol Coupling

Eugenia Andreea Dragu; Jean-Valere Naubron; Anamaria Hanganu; Alexandru C Razus; Simona Nica

doi:10.1002/chir.22523

Absolute Configuration Determination of Azulenyl Diols Isolated From Asymmetric Pinacol Coupling

Chirality. 2015 Nov;27(11):826-34. doi: 10.1002/chir.22523. Epub 2015 Sep 14.

Authors

Eugenia Andreea Dragu¹, Jean-Valere Naubron², Anamaria Hanganu¹, Alexandru C Razus¹, Simona Nica¹

Affiliations

¹ Institute of Organic Chemistry "C. D. Nenitzescu" of the Romanian Academy, Splaiul Independentei, Bucharest, Romania.
² Spectropole-Optical and CD Spectroscopies, Service D1, Marseille, France.

PMID: 26364568
DOI: 10.1002/chir.22523

Abstract

A convenient enantioselective approach for the pinacol coupling of 1-acetylazulene involving easily accessible (R)- or (S)-BINOLs as chiral additive is reported. This supposes the preformation of the chiral titanium-BINOL complex in 1:2 ratio and subsequent reduction with zinc when, 2,3-di(azulen-1-yl)butane-2,3-diol can be isolated in around 60% enantiomeric excess. The absolute configuration of the isolated enantiomers was assigned by comparison of the experimental and Boltzmann-weighted calculated VCD and ECD spectra and assigned as (+)-(2S;3S)-di(azulen-1-yl)butane-2,3-diol. Chirality 27:826-834, 2015. © 2015 Wiley Periodicals, Inc.

Keywords: 2,3-di(azulen-1-yl)butane-2,3-diol; asymmetric pinacol coupling; catalytic reactions; circular dichroism spectroscopy; theoretical calculations.