A-Nitro sulfones

The transformation of l-methylthio-l-(methylsulfonyl)alkanes (254) to methyl esters can be efficiently carried out by oxidation or by a-chlorination followed by methanolysis (equation 152)145. The lithium or the sodium salt of (phenylsulfonyl)nitromethane (256) is a very useful reagent for the preparation of higher homologues of nitromethanes by alkylation since the salts are air insensitive, non-hygroscopic, and easily handled without decomposition. The oxidation of the resulting secondary a-nitro sulfone (257) gives... 

The conversion of secondary a-nitro sulfones (257) upon treatment with 20% aqueous titanium(III) chloride in THF to nitriles has been reported (equation 157)146. 

Nitro compounds that contain an a hydrogen can be reduced to oximes with zinc dust in HOAC or with other reagents, among them CS2—Et3N, CrCl2, " and (for a-nitro sulfones) NaN02. oc-Nitro alkenes have been converted to oximes... 

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). 

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... 

Phenylsulfonyl)nitromethane is preferentially C-alkylated by ally lie acetates in the presence of Pd(PPh3)4 (5 mol%) to give various a-nitro sulfones as shown in Eq. 5.53.76... 

The reaction of a-bromo or a-iodonitroalkanes with sodium benzenesulfinate gives a-nitro sulfones in 85-95% yields (Eq. 5.73), which proceeds via SRN1 reaction (Section 5.4).117... 

Eine Mischung aus I0 mmol a>Nitro-sulfon und 30 mmol BNAH in N2-freicm DMF werden bet 20 unter Stickstoff geriihrt b Ausbeute durch GC besttimmt B isolierte Ausbeute... 

Other Reducing Agents. 1,4-Dihydropyridines have been successfully employed for the reductive desulfonylation of functionalized sulfones. Of special interest is the desulfonylation of a-nitro sulfones with BNAH under sunlight irradiation to give the corresponding nitro compounds in good yields.90,91 The reaction takes place under mild conditions and tolerates ketones, nitriles, and isolated double bonds (Eq. 120).91 A photo-induced electron-transfer employing ascorbic acid as electron donor is also an efficient approach for the reductive desulfonylation of (3-ketosulfones.197... 

Sodium Bisulfite. Sodium bisulfite [7631-90-5] NaHSO, is occasionally used to perform simultaneous reduction of a nitro group to an amine and the addition of a sulfonic acid group. For example, 4-amino-3-hydroxyl-l-naphthalenesulfonic acid [116-63-2] C qH NO S, is manufactured from 2-naphthol in a process which uses sodium bisulfite (59). The process involves nitrosation of 2-naphthol in aqueous medium, followed by addition of sodium bisulfite and acidification with sulfuric acid. 

Tin radicM-induced eliminadon from fi-nitro sulfones or fi-nitro sulfides proceeds in a stereoselecdve way to give ruin eliminadon products. " Whendiastereoraers of fi-nitro sulfones can be separated, each diastereoraer gives (Ey and fZ -alkenes selecdvely fEq. 7.111. Such... 

The base-catalyzed reaction of nitromethane with a-amidoatkyl sulfones gives the nitro compounds as in Eq. 4.117 the nitromethyl group is converted into a carboxylic group to give a-amino acids by the Nef reaction using KMn04.155... 

Tin radical-induced elimination from P-nitro sulfones or P-nitro sulfides proceeds in a stereoselective way to give anti elimination products.153 When diastereomers of P-nitro sulfones can be separated, each diastereomer gives ( )- and (Z)-alkenes selectively (Eq. 7.111). Such... 

Oxidation may be achieved in the presence of oxygen or air. Other suitable oxidants include sulfur, sodium polysulfide, iron (III) chloride, potassium ferro-cyanide (III) or potassium dichromate, peroxydisulfate or salts of aromatic nitro-sulfonic acids. An aqueous/alkaline medium is used in the presence of a high boiling organic solvent which is not miscible with water or which is almost immiscible with water. Cyclization with chlorosulfonic acid can be followed directly by oxidation with bromine to afford the thioindigo system, without separation of the intermediate. 

Based on this gathered experience the diastereoselective alkylation of enantio-pure a-lithiated sulfonates was extended to the Michael addition with aliphatic nitroolefins [95]. Thus the Michael adducts 118 could be achieved in excellent yields (84-99%) with high diastereoselectivities de of 80-88% (84 to >98% after recrystallization or chromatography). Cleavage of the chiral auxiliary and treatment with diazomethane furnished the anti-configured a,j3-disubstituted y-nitro-methyl sulfonates 119 in overall yields of 41-70% and with excellent de- and ee-values (Scheme 1.1.32). 

The reaction consists in the replacement of the nitro by a sodium sulfonate group ... 

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