R- Butyl hydroperoxide

Recently (79MI50500) Sharpless and coworkers have shown that r-butyl hydroperoxide (TBHP) epoxidations, catalyzed by molybdenum or vanadium compounds, offer advantages over peroxy acids with regard to safety, cost and, sometimes, selectivity, e.g. Scheme 73, although this is not always the case (Scheme 74). The oxidation of propene by 1-phenylethyl hydroperoxide is an important industrial route to methyloxirane (propylene oxide) (79MI5501). 

Alkyl hydroperoxides give alkoxy radicals and the hydroxyl radical. r-Butyl hydroperoxide is often used as a radical source. Detailed studies on the mechanism of the decomposition indicate that it is a more complicated process than simple unimolecular decomposition. The alkyl hydroperoxides are also sometimes used in conjunction with a transition-metal salt. Under these conditions, an alkoxy radical is produced, but the hydroxyl portion appears as hydroxide ion as the result of one-electron reduction by the metal ion. ... 

Epoxyeyclohexanone has been prepared in 30% yield4 by epoxi-dation of 2-cyclohexen-l-one with alkaline hydrogen peroxide, using a procedure described for isophorone oxide (4,4,6-trimethyl-7-oxabicyclo[4.1.0]heptan-2-one).5 A better yield (66%) was obtained using f r/-butyl hydroperoxide (1,1-dimethylethylhydroperoxide) and Triton B in benzene solution.6 The procedure described here is simple and rapid. 

In the field of free radicals and liver injury there is a vast body of work concerning a group of compounds that have proven to be of great value as experimental models but are of little clinical significance. The most frequently used compounds are quinones (particularly menadione), paraquat and diquat, bromobenzene, and organic hydroperoxides, particularly cumene hydroperoxide and r-butyl hydroperoxide (see Poli et al., 1989b). 

Chiral sulfoxides (12, 92). Chiral sulfoxides are obtained with improved enantioselectivity by substitution of cumene hydroperoxide (CHP, Aldrich) for r-butyl hydroperoxide in the Sharpless reagent.5... 

Various transition metals have been used in redox processes. For example, tandem sequences of cyclization have been initiated from malonate enolates by electron-transfer-induced oxidation with ferricenium ion Cp2pe+ (51) followed by cyclization and either radical or cationic termination (Scheme 41). ° Titanium, in the form of Cp2TiPh, has been used to initiate reductive radical cyclizations to give y- and 5-cyano esters in a 5- or 6-exo manner, respectively (Scheme 42). The Ti(III) reagent coordinates both to the C=0 and CN groups and cyclization proceeds irreversibly without formation of iminyl radical intermediates.The oxidation of benzylic and allylic alcohols in a two-phase system in the presence of r-butyl hydroperoxide, a copper catalyst, and a phase-transfer catalyst has been examined. The reactions were shown to proceed via a heterolytic mechanism however, the oxidations of related active methylene compounds (without the alcohol functionality) were determined to be free-radical processes. 

The radical chemistry of r-butyl hydroperoxide in the oxidation of activated hydrocarbons has been reported. ... 

Complex (1) is a catalyst for selective oxidation of benzylic, allylic alcohols to aldehydes, and secondary alcohols to ketones using r-butyl hydroperoxide. Primary aliphatic alcohol oxidation failed. The use of cumyl hydroperoxide as radical probe discounted the involvement of i-BuO /t-BuOO. Hammett studies p = -0.47) and kinetic isotope effects kn/ku = 4.8) have been interpreted as suggesting an Ru—OO—Bu-i intermediate oxidant. 

Pinene hydroperoxide (PHP) when compared with r-butyl hydroperoxide has been proposed as an excellent mechanistic probe in metal-catalysed oxidations. " If inter-molecular oxygen transfer from a peroxometal species to the substrate is rate limiting, the bulky PHP is unreactive, but for reaction of an oxometal species as the rate-limiting step, little or no difference is observed and only small differences in reactivity are observed when re-oxidation of the catalyst by ROOH to an active oxometal species is the rate-limiting step. 

The second manufacturing method for propylene oxide is via peroxidation of propylene, called the Halcon process after the company that invented it. Oxygen is first used to oxidize isobutane to r-butyl hydroperoxide (BHP) over a molybdenum naphthenate catalyst at 90°C and 450 psi. This oxidation occurs at the preferred tertiary carbon because a tertiary alkyl radical intermediate can be formed easily. 

Isomerization of oxepane (1) to cyclohexanol was found to occur in the presence of r-butyl hydroperoxide by a-cleavage of the oxepanyl radical intermediate (65) (76TL439). When a copper(I) chloride catalyst was present the major product was 2-(f-butyl-hydroperoxy)oxepane (77), probably also formed by a free radical pathway (Scheme 8) <80CR(291)223>. 

In the presence of diisopropyl(ethyl)amine, tetrachlorosilane reacts with r-butyl hydroperoxide to give 1 1 adduct 9 (equation 16). Alkylperoxydiorganoalkoxysilanes are prepared from the reaction of chlorodiorganooxysilane with alkyl hydroperoxides in the presence of ammonia or organic base such as pyridine or triethylamine (equations 17 and 18). 

The reaction of l,3-dichloro(tetramethyl)siloxane 12 with r-butyl hydroperoxide in the presence of pyridine in ether gave l-r-butylperoxy-3-chlorotetramethyldisiloxane 13 in 60% yield (equation 19). 

A less frequently used method involves the condensation of trimethylsilyl alkylamines with r-butyl hydroperoxide. A 20% yield of trimethyl(r-butylperoxy)silane has been obtained (equation 26)25. 

Asymmetric epoxidation of ailylic alcohols.1 Epoxidation of allylic alcohols with r-bulyl hydroperoxide in the presence of titanium(lV) isopropoxide as the metal catalyst and either diethyl D- or diethyl L-tartrate as the chiral ligand proceeds in > 90% stereoselectivity, which is independent of the substitution pattern of the allylic alcohol but dependent on the chirality of the tartrate. Suggested standard conditions are 2 equivalents of anhydrous r-butyl hydroperoxide with 1 equivalent each of the alcohol, the tartrate, and the titanium catalyst. Lesser amounts of the last two components can be used for epoxidation of reactive allylic alcohols, but it is important to use equivalent amounts of these two components. Chemical yields are in the range of 70-85%. 

Telturoxide elimination.2 Tellurides are converted to alkenes by reaction with chloramine-T, presumably via the adduct a (equation I). This elimination proceeds In low yield with r-butyl hydroperoxide. 

Oxidations. The reagent 1 oxidizes primary and secondary alcohols to carbonyl compounds in fair to good yield. It is not useful for epoxidation of simple alkenes, but it epoxidizes allylic alcohols to form a,/ -epoxy alcohols in 60-70% yield, In general, this epoxidation is more stcreospccific than that observed with r-butyl hydroperoxide in combination with Mo(CO)6 (9, 81-82). 

DIKETONES Disodium tetrachloro-palladate-r-Butyl hydroperoxide. 1-Lithio-2,4,6-trimethylbenzene. Tetra-kis(triphenylphosphine)palladium. Zinc-Copper-Isopiopyl iodide. 

Transition metal-catalyzed epoxidations, by peracids or peroxides, are complex and diverse in their reaction mechanisms (Section 5.05.4.2.2) (77MI50300). However, most advantageous conversions are possible using metal complexes. The use of r-butyl hydroperoxide with titanium tetraisopropoxide in the presence of tartrates gave asymmetric epoxides of 90-95% optical purity (80JA5974). 

Oxidation reactions r-Butyl hydroperoxide-Dialkyl tar-trate-Titanium(IV) isopropoxide, 51 m-Chloroperbenzoic acid, 76 Reduction reactions Chlorodiisopinocampheylborane, 72 Diisobutylaluminum hydride-Tin(II) chloride- (S) -1 - [ l-Methyl-2-pyrrolidi-nyljmethylpiperidine, 116 Lithium borohydride, 92 Lithium tri-sec-butylborohydride, 21 B-3-Pinanyl-9-borabicyclo[3.3.1]-nonane, 249... 

Osmium tetroxide-r-Butyl hydroperoxide, 222 p-Keto esters... 

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