Alkylation of Nitro Compounds via Alkyl Radicals

SRN I reactions using related p-nitrophenyl or p-nitrocumyl systems41 as reductive alkylating agents have been studied by Komblum and co-workers these are well summarized in the reviews.39 At the same time, Russell discovered the S l reaction of geminal halonitroalkanes with stabilized carbanions (see Eq. 5.25).42 The products are readily converted into alkenes via elimination of nitro groups (see Section 7.3). 

The cyano group is also a good electron acceptor for SrnI substrates, as shown in Eq. 5.2643 and Eq. 5.27,44 but a nitro group is a better electron acceptor than a cyano group. 

Geminal dinitro compounds 45 a-nitro sulfones 46 a-nitro esters,47 or a-nitro nitriles48 react with anions derived from nitroalkanes to give the S l products, as shown in Eqs. 5.28, 5.29, 5.30 and 5.31, respectively (Section 7.1). 

The anion of nitromethane is particularly reactive in S l reactions. Various kinds of tertiary nitro groups are replaced by a nitromethyl group on treatment with the anion of nitromethane (Section 7.1).49 2-Iodoadamantane reacts with the anion of nitromethane in the presence of acetone enolate (entrainment reaction) under irradiation of a 400-W UV lamp to give 2-ni-tromethyladamantane in 68% yield, (see Eq. 5.32).50a 1-Iodoadamantane also reacts with the anion of nitromethane in a similar way.50b 

Crozet and co-workers have used S l reactions for synthesis of new heterocycles, which are expected to be biologically active (see also Section 7.3, which discusses synthesis of alkenes). For example, 2-chloromethyl-5-nitroimidazole reacts with the anion of 2-nitropropane to give 2-isopropylidene-5-nitroimidazole. It is formed via C-alkylation of the nitronate ion followed by elimination of HN02 (Eq. 5.33).51a Other derivatives of nitroimidazoles are also good substrates for SrnI reactions.5113 0 

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