Absolute Configuration Determination of Azulenyl Diols Isolated From Asymmetric Pinacol Coupling

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.

High‐Throughput Assay for Enantiomeric Excess Determination in 1,2‐ and 1,3‐Diols and Direct Asymmetric Reaction Screening

“…Recent advances in the development of methods for the preparation of 1,2-and 1,3diols necessitate the development of high-throughput screening techniques for the fast determination of enantiomeric excess (ee), which is essential for the optimization of chiral catalysts and libraries of auxiliaries for asymmetric transformations where the ability to analyse a large number of samples in parallel fashion is highly desirable. [12] Currently, the most common methods used for the determination of enantiomeric purity involve 1 H-and 19 F-NMR spectroscopy, [13], [14], [15], [16] circular dichroism (CD), [17], [18], [19], [20] chiral-phase high performance liquid chromatography (HPLC), HPLC coupled with circular dichroism (HPLC-CD), or chiral gas chromatography (GC). [21] Such techniques are, however, better suited for serial analyses while the need for the simple parallel platforms remains largely unmet.…”

Synthesis of azulenic compounds with a homo- or hetero-atomic double bond at position 1

“…However, the addition of pyridine in these conditions increases the yields in pinacolone and alkene until the disappearance of pinacol. It should be noted that, regardless of the reaction conditions, the pinacol resulted only as a racemic mixture 60 and the (Z)…”

High-throughput assay for determining enantiomeric excess of chiral diols, amino alcohols, and amines and for direct asymmetric reaction screening

“…Separation of enantiomers has become a significant research area in analytical chemistry owing to its impact on chemical, pharmaceutical, industries, and biotechnology. Traditional methods for determination of enantiomeric purity such as 1 H-and 19 F-NMR spectroscopy, [1][2][3][4] circular dichroism (CD), [5][6][7] and chiral separation techniques such as chiral-phase high performance liquid chromatography (HPLC), 8 HPLC coupled with circular dichroism (HPLC-CD), [9][10][11] or chiral gas chromatography (GC) 12,13 and capillary electrophoresis (CE), 14 are the reliable standard methods that are most used for the separation and determination of enantiomers. 14 However, these techniques are better suited for serial analyses.…”