Deoxygenation of sulfoxides

Stannous chloride is used most frequently for the reduction of nitro compounds [177, 178, 179] and of quinones [180, 181], It is also suitable for conversion of imidoyl chlorides [182] and of nitriles [183] to aldehydes, for transformations of diazonium salts to hydrazines [184], for reduction of oximes [f[Pg.30]

Titanous chloride (titanium trichloride) is applied in aqueous solutions, sometimes in the presence of solvents increasing the miscibility of organic compounds with the aqueous phase [199, 200]. Its applications are reduction of nitro compounds [201] and cleavage of nitrogen-nitrogen bonds [202] but it is also an excellent reagent for deoxygenation of sulfoxides [203] and amine oxides [199] (Procedure 38, p. 214). 

Chemical deoxygenation of sulfoxides to sulfides was carried out by refluxing in aqueous-alcoholic solutions with stannous chloride (yields 62-93%) [186 Procedure 36, p. 214), with titanium trichloride (yields 68-91%) [203], by treatment at room temperature with molybdenum trichloride (prepared by reduction of molybdenyl chloride M0OCI3 with zinc dust in tetrahydrofuran) (yields 78-91%) [216], by heating with vanadium dichloride in aqueous tetrahydrofuran at 100° (yields 74-88%) [216], and by refluxing in aqueous methanol with chromium dichloride (yield 24%) [190], A very impressive method is the conversion of dialkyl and diaryl sulfoxides to sulfides by treatment in acetone solutions for a few minutes with 2.4 equivalents of sodium iodide and 1.2-2.6 equivalents of trifluoroacetic anhydride (isolated yields 90-98%) [655]. 

REDUCTION WITH STANNOUS CHLORIDE Deoxygenation of Sulfoxides [186]... 

Deoxygenation of sulfoxides. Sulfoxides arc reduced to sulfides in 75-95% yield by reaction with ClSi(CH,)i and zinc in THF. The reaction is exotherftlic and should be maintained below 30°. 

Deoxygenation of sulfoxides.1 This reaction can be carried out with cyanuric fluoride in dioxanc (3-9 hours, 65 80% yield). Cyanuric chloride (3, 72 4, 522 5, 687 6, 149) can be used in the case of aryl sulfoxides, but alkyl sulfoxides undergo Chlorination with this reagent. 

Deoxygenation of sulfoxides, selenoxides, oximes, and nitroalkanes.2 The reduction of sulfoxides and selenoxides is possible with PI3 or P2I4 in CH2C.l2 even at temperatures of —78°. Yields are 70-95%. 

Deoxygenation of sulfoxides.5 a-Cyano and carboalkoxy sulfoxides undergo eliminative deoxygenation with trimethylsilyl triflate in the presence of the hindered base hexamethyldisilazane to give vinyl sulfides. 

Deoxygenation of sulfoxides.1 Sulfoxides are reduced to sulfides by NaBH4 (excess) and 1 equiv. of CoCl2-6H20 in ethanol in 45-95% yield. Sulfones are inert to this reagent. 

Among other template transformations, related to modification of ligand systems, it is necessary to indicate reactions of deoxygenation of sulfoxide complexes, for instance (3.195) [417] ... 

Trichloro(methyl)silane-Sodium iodide, 11, 553-554. This in situ equivalent of io-dotrimethylsilane is also effective for cleavage of esters and lactones, selective conversion of tertiary and benzylic aleohols into iodides, dehalogenation of a-halo ketones, deoxygenation of sulfoxides, and conversion of dimethyl acetals to carbonyl compounds. ... 

Deoxygenation of sulfoxides.3 Dimethylboron bromide and 9-borabicy-clo[3.3.1]nonyl bromide (Aldrich) convert alkyl and aryl sulfoxides to sulfides at low temperature and in high yield. 

Deoxygenation of sulfoxides and azoxyarenes. This combination is superior to triphenylphosphine-iodine for deoxygenation of sulfoxides to sulfides (70-95% yield) and of azoxy benzenes to azobenzenes ( 90% yield, two examples). The reaction can be promoted by addition of sodium iodide. One advantage is that the by-product, HMPT, is soluble in water and easily removed. 

Deoxygenation of sulfoxides, selenoxides, and nitro alkanes. P2L, is a useful reagent for deoxygenation of sulfoxides, selenoxides, and primary nitroalkanes to sulfides, selenides, and nitriles, respectively. The reactions occur in less than 2 hours at2r. 

Deoxygenation of sulfoxides. This combination [(COCl)2/NaI = 1 2] reduces sulfoxides to sulfides in 75-95% yield. Oxalyl chloride can be replaced by SOCI2, POCI3, and PCI . ... 

Deoxygenation of sulfoxides. Tris(phenylseleno)borane is an effective reagent for the reduction of sulfoxides under mild conditions. Although this reagent converts ketones to selenoketals, selective deoxygenation of keto sulfoxides is possible. Deoxygenation of vinyl sulfoxides also proceeds smoothly. 

Deoxygenation of sulfoxides to sulfides Dichloroborane reduces aliphatic sulfoxides to sulfides almost quantitatively in a few minutes at 0° in THF. Reduction of aryl sulfoxides is much slower (24 hr., 25°, excess BHC12) and yields are lower. Ester,... 

Cleavage of ethers or esters, carbamates, phosphonates with trimethylsilyl iodide. Deoxygenation of sulfoxides (see 1st edition). 

Deoxygenation of sulfoxides. Sulfoxides are converted into sulfides in high yield when treated with 1 eq. of iodine and excess pyridine—sulfur dioxide complex in acetonitrile (80 ). If bromine is used, pyridine is omitted in order to... 

Deoxygenation of sulfoxides. Palladium (5%) on charcoal is an effective catalyst for hydrogenation of alkyl and aryl sulfoxides to sulfides (ethanol, autoclave, 80-90°, 1 atm. of hydrogen). Carbonyl groups are not reduced, but a carbon—carbon double bond is reduced, although more slowly than the S=0 group. 

Deoxygenation of sulfoxides. The reagent reduces unhindered sulfoxides to sulfides in a yield of 75-957o. ... 

Deoxygenation of sulfoxides. Alkyl sulfoxides are reduced to sulfides on treatment with either bromo- or iodotrimethylsilane in CCI4 at room temperature for 30 minutes (yields generally around 80%). Some halogenated products are also formed in the case of diaryl or dibenzyl sulfoxides. 

Deoxygenation of sulfoxides. Titanium(II) chloride, formed in situ by reduction of titanium(IV) chloride with zinc dust, reduces sulfoxides to sulfides at room temperature almost instantly. Ether and methylene chloride are the preferred solvents. Yields are in the range 85-95%. ... 

Deoxygenation of sulfoxides. This reaction can be carried out with triphenyl-phosphine activated by iodine (1 equiv.) in refluxing acetonitrile in 10-60 minutes. Sodium iodide is added to increase the rate. Sulfides are obtained in 70-957, yield. ... 

Deoxygenation of sulfoxides. MoOCla-zinc or VCI3 reduces sulfoxides to sulfides in 75-90% yield. ... 

Deoxygenation of sulfoxides by NaBHa is effected by the combination of CoCl2 6H20 and moist alumina in hexane (eq 37). The reactivity is a function of steric hindrance. When the combination of TPPFe Cl and NaBHa was used, sulfilimines could be as smoothly reduced as the sulfoxides. ... 

Chemoselective Deo iQtgenation of Sulfoxides. DBBS is an exceptionally effective reagent for the rapid deoxygenation of sulfoxides to sulfides. Aliphatic and aromatic sulfoxides undergo deoxygenation in <15 min at room temperature in CH2CI2 to afford sulfides in excellent chemical yields (eq 24). ... 

Narayana, C., Padmanabhan, S., Kabalka, G. W. 1991. Reductive dimerization of sulfonyl derivatives to disulfides and deoxygenation of sulfoxides to sulfides using the boron triiodide-A,A-diethylaniline complex. Synlett 125-126. 

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