Diazo ketones, epoxy

A reaction between a-diazo ketones and a,(1-unsaturated aldehydes under rhodium(ll)-catalysis provides a route to epoxy-bridged tetrahydropyran-4-ones <2002JOC8019>. This methodology allows entry to functionalized spiro-dioxa-bridged polycyclic frameworks <2002TL3931, 2003T8117>. 

The condensation of l-chloro-3-diazopiopanone (57) with aldehydes provides epoxy diazo ketones (equation 18). Treatment of a methanolic solution of (57) and benzaldehyde, in a stoichiometric ratio, with aqueous sodium hydroxide furnishes l-diazo-3,4-epoxy-4-phenyl-2-butanone (59a) in 69% yield the rrans-epoxide is obtained stereoselectively, analogous to the Darzens condensation of benzaldehyde and chloroacetone. The reaction is reported to proceed to give also the diazo ketones (59b-59e), and the epoxides obtained are exclusively of the trans configuration. ... 

Photochemical Wolff rearrangement of 2-diazo-3-ketones, though not widely used as a source of A-norsteroids, is discussed in section V in connection with the mechanism of the important photochemical synthesis of D-norsteroids. Photochemical rearrangement of epoxy ketones is a source of A-nosteroids these rearrangements are discussed in chapter 13. Other photochemical routes to A-norsteroids are known." " ... 

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