Bromonitro compounds

Nucleophilic substitution reactions in the selenophene series have attracted some interest. Debromination of bromonitro compounds [(50, X = S, Se) and (53, X = S, Se)] with sodium thiophenoxide and sodium selenophen-oxide72 was studied. Selenophene compounds were four times more reactive than the thiophene derivatives. The position of attack, a or /), had very little influence on the rate ratio. The kinetics of the side-chain nucleophilic reactions of selenophene derivatives, shown in Scheme 4, has been reported.7 3... 

Alkenes can be nitromeicurated (HgQ2/2 NaNOs/H20, 30 h, 25 Q and the products can be bromo-demercurated, giving bromonitro compounds. An alternative woik-up with base provides a valuable nitroalkene synthesis (Scheme 84). °... 

Olefin synthesis. Komblum et al. have described a new synthesis of tetrasubsti-tuted olehns from vicinal dinitro compounds. There are several methods for conversion of aliphatic and alicyclic nitro compounds into w c-dinitro compounds, the most useful of which is a procedure of Seigle and Hass. AnitroparaHin is converted into the lithium salt (I) by treatment with lithium methoxide and this is then treated with bromine to form a bromonitro compound (2). Reaclion of (2) with a second equivalent of the nitro-... 

The first step was the bromination of the oxime with bromocuccinimide to yield a bromonitroso compound on which the oxidation of hydrogen peroxide with nitric acid was transformed into bromonitro compound. The latter by acting with sodium borohydride furnished a secondary nitro compound with a yield of 33-80%. The method was particularly suitable for the formation of nitro derivatives of nitro cycloalkanes. The method is unsuitable for aromatic ketoximes and aldoximes. However, Barnes and Patterson [73] extended the method to aldoximes by using ozone as an oxidizing agent on gem-chloro ... 

Toluene-p-sulphonic acid monohydrate promotes hydration of imine double bonds, providing a method for the ready regeneration of ketones from their 2,4-dinitrophenylhydrazones this method is unsuitable for regeneration of a S-unsaturated ketones, where extensive retro-aldol fragmentation occurs. Imines can be oxidized photochemically to ketones. In a re-investigation of the acid-catalysed conversion of ew-bromonitro-compounds into ketones, loss of a bromonium ion followed by a Nef reaction is postulated (Scheme 70). ... 

Rates of debromination of bromonitro-thiophenes and -selenophenes with sodium thio-phenoxide and sodium selenophenoxide have been studied. Selenophene compounds were about four times more reactive than the corresponding thiophene derivatives. The rate ratio was not significantly different whether attack was occurring at the a- or /3-position. As in benzenoid chemistry, numerous nucleophilic displacement reactions are found to be copper catalyzed. Illustrative of these reactions is the displacement of bromide from 3-bromothiophene-2-carboxylic acid and 3-bromothiophene-4-carboxylic acid by active methylene compounds (e.g. AcCH2C02Et) in the presence of copper and sodium ethoxide (Scheme 77) (75JCS(P1)1390). 

Denitrocyclization strategy is potentially useful for the synthesis of a wide range of tricyclic compounds. The approach was found useful for the synthesis of thienobenzothiazole 339 and 343 starting from the corresponding bromonitro-thiophenes 336 and 340, respectively (Scheme 52) (68MI2, 72IJS(B)109). 

In attempts to prepare a spiro-2 -oxocine (105), Fischer s base was allowed to react with 2-hydroxycinnamaldehyde and its a-ethyl-5-nitro, 5-bromo, 3,5-dibromo, 3-bromo-5-nitro, and 3,5-dinitro derivatives. As with the oxepines, the dicon-densed product (106) was formed in the first four cases listed (36-72% yield), and the black, crystalline open form (107) of the desired product was formed (69%) with the dinitro derivative. The bromonitro intermediate gave a mixture of the dicon-densed product and the open form of the desired monocondensed product. In this series also, none of the compounds exhibited any photochromic properties.101... 

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