Facile synthesis of enantiomerically pure 1-(5-bromo-2-chlorophenyl)-1-(4-ethoxyphenyl)ethane

Abstract

A facile 7-step procedure for the synthesis of enantiomerically pure 1-(5-bromo-2-chlorophenyl)-1-(4-ethoxyphenyl)ethanes[(R)-2 and(S)-2] that started from (5-bromo-2-chlorophenyl)(4-ethoxyphenyl)methanone 3 was developed. The key step was the resolution of 2-(5-bromo-2-chlorophenyl)-2-(4-ethoxyphenyl)acetic acid 6 by crystallizations of its L- and D-menthyl esters 7 and 8 from petroleum ether to give optically pure enantiomers 9 and 10, respectively. The absolute configurations of the products were unambiguously determined by single-crystal X-ray diffractions of four key intermediates, 9, 10, 13 and 14. This procedure is characterized by inexpensiveness, scalability and ability to produce two individual enantiomers of a diarylethane with unambiguously determined absolute configurations and high enantiomeric purities.

Keywords

Diarylethane / Diastereomer / Enantiomer / Resolution / SGLT2 inhibitor

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