Phenyltrimethylammonium perbromide

Dich lorotris(triphenylphosphine)-ruthenium. Dimethyl(2,4,6-tri-/-butylphenoxy)chlorosilane. Lithiocyclopropyl phenyl sulfide. Nafion-H. PaLIadium(II) acetate-1,2-Bis(diphenylphosphino)ethane. Palladium(II) chloride. Phenyltrimethylammonium perbromide. Potassium hydride. Potassium permanganate. 2-Pyridylsclcnenyl bromide. 

PhenyH,2,4-triazoline-3,5-dione, 381-382 Phenyltrifluoromethylketene, 383-384 Phenyl(trifluoromethy))mercury, 384-385 Phenyl(trihalomethyl)mcicury, 385 Phenyltrimethylammonium perbromide,... 

Other reactions. Pyridinium hydrobromide perbromide is reported to be the most satisfactory reagent for the conversion of indole into 3-bromoindole. The reagent can be used for the selective bromination of cyclic ketals in tetrahydroftirane solution, but phenyltrimethylammonium perbromide is now the preferred reagent. 

Fetizon et al.3 used this reaction in a new synthesis of A2-steroids from 3-keto-steroids. For example, dihydrotestosterone acetate (1) is converted in high yield into the 2a-bromoketone (2) with phenyltrimethylammonium perbromide (1, 855). The a-bromoketone is then heated for 3 hours with freshly distilled triethyl phosphite to give the enol phosphate (3). On reduction of (3) with lithium in liquid... 

Heterocyclic pseudoquinones Treatment of the known diketones(1) with bromine or phenyltrimethylammonium perbromide (1, 855-856) leads to the... 

Ando and coworkers have developed a synthesis of (+)-tuberiferin (11a) from tetrahydrosantonin 3b [10] (Scheme 2). These authors noticed that the Of-methylene-/-lactone moiety was stable under acidic and mild basic conditions and also to bromination by phenyltrimethylammonium perbromide (PTAB), and so the introduction of this moiety was carried out at an early stage of the synthesis. This approach was shown to be more efficient than other previous routes, in which the introduction of the a-methylene-/-lactone was left to the final stage. Thus, after acetalization of the C(3) carbonyl group of 3b the C(11)-C(13) methylene group was formed by the Grieco method, which involves phenylselenylation to give... 

Btomomethyl ketones. Direct bromination of methyl ketones as a route to bromomethyl ketones is usually unsatisfactory because bromine mainly attacks the more substituted carbon. One expedient is reaction of ketals of the ketone with phenyltrimethylammonium perbromide (1,855) or with bromine in methanol. Actually methyl ketones can be brominated directly with bromine in methanol, but the regiospeciflcity depends on the structure of the ketone. Thus l-bromo-3-methyl-2-butanone (2) can be obtained directly from (1) in good yield as shown in equation (I). It should be noted that dimethyl ketals are formed as well and must be hydrolyzed during work-up. ... 

The oxidative formation of azulenoquinones from linearly fused azulenoheterocycles, on the other hand, exactly follows the rules of electrophilic substitution on azulenes (cf. Section 4.2.1). Thiophene 45a or furan 47a (Scheme 68) can be oxidized by bromine/aqueous acetic acid, phenyltrimethylammonium perbromide (PTAB) or pyridinium perbro-mide to yield mixtures of quinones 274a and 275a or 274b and 275b, respectively (96BCJ1149, 03H(61)271). 

Phenyltrimethylammonium perbromide reacts like pyridinium perbromide but is easier to prepare and more stable. It dissolves easily in tetrahydrofuran, in which these reactions are performed. It monobromi-nates selectively ketones and cyclic ketals in a-posi-tion without affecting double bonds and reactive benzene rings.—E 2-Acetyl-6-methoxynaphthalene- 2-(co-bromoacetyl)-6-methoxynaphthalene. Y 80%. 

---