The first enantioselective [3+2] cycloaddition of epoxides to arylisocyanates: asymmetric synthesis of chiral oxazolidinone phosphonates

A [3+2] cycloaddition of diethyl 1,2-oxiranephosphonate to aryl isocyanates catalyzed by lanthanide cations is described. The reaction is highly regioselective and 5-substituted 2-oxazolidinone phosphonates are obtained with a regioselectivity greater than 95:5 with respect to the 4-substituted regioisomer, and in up to 84% yield. When 20 mol % of Pybox-Yb3+ is used as a catalyst, enantiomerically enriched products are obtained in up to 75% ee, depending on the reaction conditions, and the nature of the isocyanate. Low temperatures benefit asymmetric induction, but have an adverse effect on the regioselectivity for para-substituted aryl isocyanates.

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