Epoxides epoxidation-spirocyclization method

A similar epoxidation-spirocyclization method has been used recently by Denmark et al. [142, 143] in their synthesis of papulacandin D, as well as in an independent study [144] toward papulacandin analogues (Scheme 69). 

Another standard method for the synthesis of 2-oxazolidinones is by reaction of epoxides with isocyanates. Although 4,5-disubstituted derivatives are not readily accessible by this route, it has been shown that iminodioxolanes (192) add to epoxides in the presence of AICI3 to afford these oxazolidinones in high yield <9lJOC2684>. The reaction proceeds through a spirocyclic intermediate (193) (Scheme 96). The reaction of vinyl epoxides with aryl isocyanates is facilitated by palladium catalysis (Equation (28)) <89TL3893>. The products are obtained by a double inversion process, but... 

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