Phenyl hydroperoxide, substituted

Phenyl hydroperoxide, C-O distance, 103 (y-Phenylhydroperoxides, nucleophiUc substitution cyclization, 234-5 1 -Phenyl-3-methyl-3-butene, intrazeohte photooxygenation, 874-5 Phenyl substituted alkenes, photooxidation site selectivity, 839-42... 

Alkyl- and aryl-hydrazones of aldehydes and ketones readily peroxidise in solution and rearrange to azo hydroperoxides [1], some of which are explosively unstable [2], Dry samples of the p-bromo- and p-fluoro-hydroperoxybenzylazobenzenes, prepared by oxygenation of benzene solutions of the phenylhydrazones, exploded while on filter paper in the dark, initiated by vibration of the table or tapping the paper. Samples were later stored moist with benzene at —60°C to prevent explosion [3], A series of a-phenylazo hydroperoxides derived from the phenyl-or p-bromophcnyl-hydrazones of acetone, acetophenone or cyclohexanone, and useful for epoxidation of alkenes, are all explosive [4], The stability of several substituted phenylazo hydroperoxides was found to be strongly controlled by novel substituent effects [5],... 

These intrazeolite singlet oxygen ene reactions have synthetic potential because the cis effect observed in solution is suppressed in the zeolite [13]. Consequently, allylic hydroperoxides which are inaccessible by other routes may be available via this new technology. For example, photo-oxidations of aryl-substituted alkenes, 7, in sensitizer-doped NaY react to generate the allylic hydroperoxides as the major or exclusive product [17]. In contrast, in solution, the hydroperoxides are formed in only 5-20% yields, with 2-1-2 and 4-1-2 adducts dominating the reaction mixtures. In the case of 2-methyl-5-phenyl-2-hexene, 8, the regio-selectivity for 8b and 8c improved from 47% to 94% and the diastereoselectivity from 10% to 44% as the reaction is moved from solution into the zeolite [18] ... 

In a search for more effective approaches to the problem of stereoselective dioxygenation, alternative methods have been developed. While the inclusion of alkenes and O2 within a chiral cyclodextrin cavity furnished hydroperoxides with modest ee values, neighboring stereocenters and chiral auxiliaries could induce highly stereoselective dioxygenation. In 1987 Kropf and Reichwaldt, and three years later Adam and coworkers reported on the photooxygenation of phenyl-substituted alkenes 36 producing allyUc hydroperoxides 37 and 38 with high diastereoselectivity (dr 80/20). In the best example... 

Compared to metal-catalyzed asymmetric epoxidation reactions, asymmetric versions of this reaction without the need of a catalyst (apart from a base) are rarely known. In 2000 Adam and coworkers reported a method for the asymmetric Weitz-Scheffer epoxidation of substituted enones 91 by the secondary, optically active hydroperoxide (5 )-(l-phenyl)ethyl hydroperoxide (equation 27, Table 10). ... 

TABLE 10. Enantioselective Weitz-Scheffer epoxidation of substituted enones p-XC6H4C(0)CH= CR with (5)-(l-phenyl)ethyl hydroperoxide... 

Table 17) with two substituents in position C3 the oxygen transfer by the chiral hydroperoxides occurred from the same enantioface of the double bond, while epoxidation of the (ii)-phenyl-substituted substrates 142c,g,i resulted in the formation of the opposite epoxide enantiomer in excess. In 2000 Hamann and coworkers reported a new saturated protected carbohydrate hydroperoxide 69b , which showed high asymmetric induction in the vanadium-catalyzed epoxidation reaction of 3-methyl-2-buten-l-ol. The ee of 90% obtained was a milestone in the field of stereoselective oxygen transfer with optically active hydroperoxides. Unfortunately, the tertiary allylic alcohol 2-methyl-3-buten-2-ol was epoxidized with low enantioselectivity (ee 18%) with the same catalytic system . 

As discussed in previous paragraphs, a disadvantage of TS-1 catalyst is its limited pore size, which restricts the number of oxidants that can be employed ° °. By using larger pore molecular sieves this restriction could be overcome. Titanium-substituted MCM-41 ° and titanium-grafted MCM-41 were shown to be particularly active in the epoxidation of bulky olefins like pinene and norbornene with TBHP. In the case of Ti-MCM-41 silicas, the importance of hydrophobicity in the system was demonstrated by the faster reaction rate observed with 2-methyl-l-phenyl-2-propyl hydroperoxide as the oxygen atom... 

In the presence of iron(II) sulfate, /cH-butyl hydroperoxide decomposes to yield acetone and methyl radicals, For a discussion of the kinetics and mechanism of purine C8 methylation by methyl radicals see ref 50. Reaction of adenine with benzenediazonium ions yields ( )-6-(3-phenyl-2-triazen-l-yl)purinc (7, Ar = Ph), which undergoes a C-arylation reaction, probably involving an intermolecular free-radical substitution at C8, to give 8. " ... 

Molecular complexes between substituted anilines and some hydroperoxides are mainly due to the OOH N hydrogen bonding interaction, as tested by infrared absorption spectral data121. In CCI4 solution there is evidence for the presence of both O—H N and O H—N interactions. The predominance of one of these types of interaction is affected by the structure of the hydroperoxide and by the substituent bonded to the phenyl ring of aniline. The high acidity of some hydroperoxides, such as 1,1-diphenylhydroperoxide and a-cumyl hydroperoxide, is responsible for the salt character of the formed N+—H O ion pair. 

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