Despite the increasing number of methods available, stereoselective synthesis of oxepanes has remained a challenge due to enthalpic and entropic barriers associated with medium-sized cyclic ethers. Current methods possess limitations, including preferential formation of thermodynamically more favorable a,a�-cis-oxepanes and scarcity of catalytic methods. The presence of oxepanes in nature further fuels the need for efficient preparations. Therefore, our aim has been to develop an approach for the catalytic, stereoselective synthesis of oxepanes employing easily accessible chiral substrates. Herein, we report the stereoselective synthesis of a,a�-trans-oxepanes via the organocatalytic oxa-conjugate addition reaction promoted by the gem-disubstituent effect of a 1,3-dithiane group. Our investigations revealed that a,a�-trans-oxepanes could be formed with diastereoselectivities up to >20:1 in good yields.

Stereoselective synthesis of a,a'-<i>trans-</i>oxepanes through an organocatalytic oxa-conjugate addition reaction

247th National Meeting (2014)

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Stereoselective synthesis of a,a'-trans-oxepanes through an organocatalytic oxa-conjugate addition reaction