Pd-Catalyzed Allylic C-Alkylation of Nitro Compounds

NuH = CH2(C02R)2, CH2(CN)C02R, CH2(S02Ph)C02R, CH2(N02)C02R, CH2(N02)S02Ph CH2(S02Ph)2, etc. 

The monoanions of primary nitroalkanes, phenylnitromethane, and a-nitro esters are all preferentially C-alkylated by cinnamyl acetate and 2-butenyl acetate in 50-89% yield in the presence of Pd catalyst (Eq. 5.51).75 The a-nitro ester gives the C-alkylate in 89% yield, but 2-nitropropane gives the C-alkylate in only 29% yield. The main product is cinnamaldehyde, which is derived from 0-alkylation.75a 

Wade and coworkers have found that a-nitro sulfones are useful reagents in organic synthesis because they are converted into nitroalkanes, nitriles, or carboxylic acids (see Eq. 5.52).76 

Allylic carbonates are better electrophiles than allylic acetates for the palladium-catalyzed allylic alkylation.77 Reaction of Eq. 5.54 shows the selective allylic alkylation of a-nitro ester with allylic carbonates without affecting allylic acetates.78 

As the nitro group is removed by radical denitration with Bu3SnH, allylic alkylation of a-nitro ketones with allyl carbonates in the presence of Pd(0) followed by denitration with Bu3SnH provides a new regio-selective allylation of ketones under neutral conditions (Eq. 5.55).79 

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