Thioether–phosphinite and diphosphinite ligands derived from d-xylose for the copper-catalyzed asymmetric 1,4-addition to 2-cyclohexenone

A series of thioether–phosphinite 1–3 and diphosphinite 4 and 5 ligands, derived from inexpensive d-(+)-xylose, were tested for the first time in the Cu-catalyzed asymmetric 1,4-addition to 2-cyclohexenone 6. Good enantioselectivities (up to 72%) and activities [TOF up to >1225 mol (mol h−1)] combined with excellent selectivity in the 1,4 product were obtained. Our results show that activity and selectivity (chemo- and enantioselectivity) depend strongly on the type of functional group at the C-5 position of the carbohydrate backbone, the steric properties of the substituent in the thioether moiety, the catalyst precursor and the alkylating agent.

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