Spirocyclopropane oxazolidinone

The Ti-mediated reactions for construction of cyclopropane derivatives in the presence of Grignard reagents have also been reported [188]. These methodologies have provided convenient approaches to the synthesis of spirocyclopropane oxazolidinones or trifunctionalized propane derivatives. 

It is noteworthy that the substituent at C-2 appears to be very important for the diastereoselectivity at C-2. The unsubstituted methyl 2-chloro-2-cyclopro-pylideneacetate 1-Me and the spirocyclopropanated analogs 2c-Me, 2c-Bn add the oxazolidinone 100 to form 102a-Me, 102c-Me and 102c-Bn only with moderate selectivities (diastereomer ratios were 3 1, 42 11 34 13 and 27 59 14, respectively) [10b,21]. 

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