Sulfides, r-butyl

Cyclizations. Formation of five-membered rings is favored. For example, the bis(phenylthio)acetal of 5-hexenal gives 2-methylcyclopentyl phenyl sulfide. r-Butyl... 

Related Reagents. Benzyl Chloromethyl Sulfide r-Butyl Chloromethyl Ether 2-Chloroethyl Chloromethyl Ether Chloromethyl Methyl Ether Chloromethyl Methyl Sulfide (p-Methoxy-benzyloxy)methyl Chloride 2-Methoxyethoxymethyl Chloride 2-(Trimethylsilyl)ethoxymethyl Chloride. 

Komori and Nonaka132,133 electrochemically oxidized methyl, isopropyl, n-butyl, isobutyl, r-butyl and cyclohexyl phenyl sulfides (108) and cyclohexyl p-tolyl sulfide (109) to their sulfoxides using a variety of polyamino acid-coated electrodes to obtain the range of e.e. values shown in parentheses. The highest enantiomeric purities were obtained using an electrode doubly coated with polypyrrole and poly(L-valine), an electrode which also proved the most durable of those prepared. 

Hexfluorophosphate salts behave similarly.108 The diazonium tetrafluoroborates can be prepared either by precipitation from an aqueous solution by fluoroboric acid109 or by anhydrous diazotization in ether, THF, or acetonitrile using r-butyl nitrite and boron trifluoride.110 Somewhat milder reaction conditions can be achieved by reaction of aryl diazo sulfide adducts with pyridine-HF in the presence of AgF or AgNQ3. 

B. Electron transfer reaction of r-butyl perbenzoates with dimethyl sulfides. 

Under these strong acid conditions, products from other rearrangements and acid cleavage reactions are sometimes found. For example, a mixture of 5-r-butyl-3-methyl-benzo[6]thiophene (the expected product), 6-f-butyl-3-methyIbenzo[6]thiophene and 3-methy benzo[6]thiophene was obtained on cyclization of p-t- butylphenylthioacetone with phosphorus pentoxide. During the cyclization of phenyl phenacyl sulfide to give a mixture of 2- and/or 3-phenylbenzo[Z ]thiophenes, small amounts of diphenyl disulfide and 5-pheny thio-3-phenylbenzo[6]thiophene were also formed (70AHC(11)177). 

Table 6C. 1 lists representative results for the asymmetric oxidation of thio ethers with r-butyl hydroperoxide under the standard conditions (in dichloromethane at -20°C). Enantioselectivi-ties are especially good (80-95% ee) for the oxidation of aryl methyl sufoxides (Table 6C.1). A substantial decrease in enantioselectivity is observed for oxidation of aryl-S-alkyl-type sulfides in which an alkyl group is larger than methyl such as n-propyl an n-butyl.

CF3COOH, PhSH, 20°, 1 h, 100% yield.18 Thiophenol is used to scavenge the liberated r-butyl cations, thus preventing alkylation of methionine or tryptophan. Other scavengers such as anisole, thioanisole, thiocresol, cre-sol, and dimethyl sulfide have also been used.19... 

The next step was to introduce the alkyl chain—this was best done by first oxidizing the sulfide to a sulfoxide, using sodium periodate. The sulfoxide was then deprotonated with -BuLi and alkylated with an alkyl iodide containing a carboxylic acid protected as its r-butyl ester. Reduction of the sulfoxide and hydrolysis back to the free acid gave biotin. 

Several medio are available for the intnxluction of sulfenyl groups a to carbonyl derivatives and these have been reviewed. - The most versatile procedure involves reaction of the enolate with an appropriate thiol derivative, but the preferred m od is largely dependent on the nature of the substrate employed (see below). In most instances, sulfur has been introduced in the divalent state and subsequently oxidized, although the oxidative step has been avoided by the direct introduction of sulfur at the S oxidation level. The oxidation of sulfides to sulfoxides is a trivial procedure that can be effected by a variety of reagents. Sodium metaperiodate, m-chloroperbenzoic acid and hydrogen peroxide are the most common oxidants, but r-butyl hydroperoxide, r-butyl hypochlorite, N-chlorobenzotriazole,... 

Organic peroxides such as cyclohexyl or r-butyl hydroperoxide and benzoyl peroxides can oxidize various sulfides to the corresponding sulfoxides where oxidation with TBHP in alcohols or benzene appears to be synthetically useful. 2-Hydroperoxyhexafluoro-2-propanol [(Cp3)2C(OH)OOH], formed in situ from hexafluoroacetone and H2O2, is also a very effective and convenient reagent for this puipose. 4a-Hydroperoxylumifiavin (14) oxidizes sulfides to sulfoxides in organic solvents such as Bu OH or dioxane at 30 C much more effectively than The reactivi of the flavins was... 

This reaction is analogous to similar methods for the preparation of ethers (methods 113 and 116), Both simple and mixed sulfides may be made from aliphatic mercaptans or thiophenols. The sodium mercaptides are formed from the mercaptans and aqueous or alcoholic solutions of sodium hydroxide or alcoholic sodium ethoxide. Alkylation is effected by halides, alkyl sulfates, or esters of sulfonic acids. The over-all yields of sulfides are usually above 70%. r-Butyl mercaptan is alkylated directly by /-butyl alcohol in strong sulfuric acid to give /-butyl sulfide in 87% yield. ... 

The dehydrogenation of bis(a-bromobenzyl) sulfide (41) with Fe2(CO)9 in the presence of furan affords (43). The iron-stabilized sulfur ylide (42) has been proposed as intermediate. Reaction of C -di-phenylnitrone (44) with l,2-bis(methylene)-3,3.4,4,5,5-hexamethylcyclopentane (45) in benzene at 80 C gives a [4 -I- 3] cycloadduct (46 18%), along with some other products. Landor et al. have shown that the dehydrobromination of allenyl bromide (47) in the presence of furan affords bicyclic ketone (49) in 9% yield. Apparently, a strain alkyne intermediate reacts with r-butyl alcohol to afford an enol ether (48), which is then converted to (49) (Scheme 11). 

OxUatiou of primary and secondary alcohals to carbonyl compounds. Corey and Kim report that the complex of N-chlorosuccinimide and dimethyl sulfide is somewhat superior to the complex of dimethyl sulfide and chlorine (this volume) for oxidation of primary and secondary alcohols the formation of hydrogen chloride is avoided and yields are generally higher. The procedure is illustrated for the oxidation of 4-r-butyl-cyclohexanol (2) to 4-r-butylcyclohexanonc (4). The complex (1) is prepared by addition of dimethyl sulfide (4.1 mmole) to a stirred solution of NCS (3.0 mmole) in toluene at 0° under argon. The mixture is cooled to -25° and a solution of 4-r-butylcyclo-hexanol (2.0 mmole, mixture of cis and trans) in toluene is added dropwise. The stirring is continued for 2 hr. at — 25° and then triethylamine (3.0 mmole) in toluene is added dropwise. The ketone (4) is obtained in almost quantitative yield. As in oxidation with the complex of dimethyl sulfide and chlorine, an intermediate sulfoxonium complex (3) is involved. 

Additions of the Michael type of nucleophiles to the carbon-carbon double bond of thiete 1,1-dioxides to give 3-substituted thietane 1,1-dioxides occur readily. The addition of hydrogen has been discussed in Section A. Nucleophiles include cyanide, the anion of nitroethane, the lithium salt of r-butyl o-tolyl sulfone, dimethylamine, cyclohexylamine, ethoxide, and hydrogen sulfide. The reaction is exemplified by the synthesis of 278. Additions to 3-chloro-2H-thiete 1,1-dioxide most likely proceed by an addition-elimination mechanism an example is shown for the addition of the anion of dimethylmalonate to give 279. The replacement of a 3-morpholinyl group by a 3-A methyl-A-phenylamino group in thiete 1,1-dioxide is another example of addition-elimination. An addition of ethoxide with elimination of p-nitrophenyl anion may occur with 268 (Ar = / -N02C6H4). " Addition of bromine via N-bromo-succinimide to the double bond of 4-phenyl-2H-thiete 1,1-dioxide occurs only in 1.5% yield. ... 

The indirect reduction of r-butyldimethylsulfonium perchlorate using the anion of 1,4-dihydro-1-methylpyridine as mediator to dimethyl sulfide and 4-r-butyl-1,4-dihydro-1-methylpyridine has been important for the understanding of electron transfer in the ali-phatisk nucleophilic substitution [115]. 

The availability of f j-di-r-butyl disulfide monoxide from selective oxidation catalyzed by vanadyl-88 enables the preparation of chiral r-butyl sulfinamides, sulfoxides, and sulfinimines. Very similar reaction conditions bring about the transformation of various 1,3-dithianes to chiral monoxides. (/ ,Rl-2,2,5,5-Tetramethyl-3,4-hexanediol is a chiral ligand for the Ti(IV)-catalyzed oxidation of sulfides with cumene hydroperoxide. ... 

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