Heavily substituted cyclopropane esters were prepared in high yields, complete diastereoselection and high (up to 96%) enantioselectivity. The reaction described herein entailed reacting 4-nitro-5-styrylisoxazoles, a class of cinnamate synthetic equivalent, with 2-bromomalonate esters under the catalysis of 5 mol% of a Cincona derived phase-transfer catalyst. The reaction allowed multi-gram preparation of desired products.

The reaction between 3-methyl-4-nitro-5-styrylisoxazoles and ethyl isocyanoacetate proceeded under phase transfer catalysis to give enantioenriched monoadducts in high enantiomeric excess (up to 99% ee). The resulting adducts were subsequently cyclised to give 2,3-dihydropyrroles and substituted pyrrolidines in identical high ees and as a single diastereoisomer.

Phase Transfer Catalyzed Enantioselective Cyclopropanation of 4-Nitro-5-styrylisoxazoles. -The cyclopropanation of styryl isoxazoles (I) as cinnamate equivalents with bromomalonate (II) in the presence of a Cinchona alkaloid derived phase-transfer catalyst affords highly substituted cyclopropanes (III) in high yields, complete diastereo-and high enantioselectivity. The masked carboxylate group is readily released by oxidative isoxazole cleavage [cf. (V)]. -(DEL FIANDRA, C.; PIRAS, L.; FINI, F.; DISETTI, P.; MOCCIA, M.; ADAMO*, M. F. A.; Chem. Commun. (Cambridge) 48 (2012) 32, 3863-3865, http://dx.doi.org/10.1039/c2cc30401e ; Dep. Pharm. Med. Chem., R. Coll. Surg. Ire., Dublin 2, Ire.; Eng.) -M. Paetzel 32-050

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