Nitrocyclopropanes functionalized

McCooey, S.H., McCabe, T. and Connon, S.J. (2006) Stereoselective synthesis of highly functionalized nitrocyclopropanes via organocatal)4ic conjugate addition to nitroalkenes. The Journal of Organic Chemistry, 71, 7494-7497. 

Unfortunately, only two attempts were made to use this approach in the synthesis of five-membered cyclic nitronates (5), and only one of them could be considered as successful. In the latter case, isomeric nitrocyclopropane was obtained as the major product. Only a-functionalized nitro alcohols are readily involved in the Mitsunobu cyclization. However, the possibility of isomerization of by-products, nitrocyclopropanes, which was mentioned in the discussion of Scheme 3.16, caused the revision of this process as a procedure for the synthesis of five-membered cyclic nitronates. (A new approach to the synthesis of initial y-nitro alcohols from readily available AN was documented in Reference 64)... 

In addition to conventional generation of carbenes from nitrodiazo compounds (22) (79), target intermediates C can be prepared by oxidation of functionalized AN CH2XNO2 with phenyliodonium diacetate. The reactions of Rhodium intermediates with certain olefins afford the corresponding cyclopropanes (23). The cycloaddition reaction was performed in the presence of a catalyst. (The successful synthesis of nitrocyclopropanes from trinitromethane derivatives and nitroacetic ester was also documented (81)). 

Therefore, all prerequisites are present for the development of a general strategy for the synthesis of nitronates (24) from a-functionalized primary AN through stabilized carbenium intermediates and nitrocyclopropanes (23). This approach allows the stereoselective synthesis of nitronates (24) from simple molecules (Scheme 3.29). 

Other types of conjugate additions with chiral thioureas were also explored by Connon. P-Substituted nitro-olefms were used in the conjugate addition reaction with dimethyl chloromalonate 115 to generate chiral, functionalized nitrocyclopro-panes [73]. Utility of the nitrocyclopropanes was demonstrated in the one-step modification towards other functionalized chiral building blocks (Scheme 24). 

Nitrocyclopropanes also undergo ring cleavage on treatment with sodiomalonate with expulsion of the nitro function providing 600 (equation 212) °. ... 

The boronate-urea (132)-catalysed formal 3 + 3-cycloaddition reactions of nitrones (130) and nitrocyclopropane carboxylates (131) produced highly functionalized... 

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