Tert-Butyl bromide, derivative

In the polar reaction, a proton in HBr first adds to the terminal sp2 carbon in isobutene to produce a stable tert-butyl cation (8), and then it reacts with the counter bromide anion to form tert-butyl bromide. Thus, the proton in HBr adds to the less substituted sp2 carbon in alkene to produce a more stable carbocation. This is based on the Markovnikov rule. In radical reactions, the hydrogen atom of HBr is abstracted first by the initiator, PhCO (or Ph ) derived from (PhC02)2, and the formed bromine atom then adds to the terminal sp2 carbon in isobutene to form the stable (3-bromo tert-butyl radical (9), and then it reacts with HBr to produce /so-butyl bromide and a bromine atom. This bromine atom again... 

The chloromercuric derivative of furan is also suitable for alkylation. When tert-butyl bromide is added to the solution of this compound in chloroform, an exothermic reaction takes place. Three products were isolated from the reaction mixture, with 2,5-di-ieri-butylfuran in moderate yield131 ... 

Stereoselective alkylation with aliphatic bromides and iodides of the Schiff bases of tert-butyl glycinate with (—)-(15,25,55)-2-hydroxypinan-3-one or (+)-(lR,2R,5R)-2-hydroxy-pinan-3-one 150 was reported to produce lipidated amino acids as d- and L-enantiomers in 80 to over 90% ee. 151 Similarly, the asymmetric synthesis of a derivative of arachidonic acid (4) has also been reported. The pure enantiomer was obtained via regioselective functionalization of a chirally pure glutamic acid. 152 ... 

The effect of various surfactants, the cationics-eetyl trimethyl ammonium bromide (CTAB), and cetyl pyridinium chloride (CPC), the anionic-sodium lauryl sulfate (SLS), and the nonionic-polysorbate 80 (Tween 80), on the solubility and ionization constants of some sparingly soluble weak acids of pharmaceutical interest was studied (Gerakis et al., 1993). Benzoic acid (and its 3-methyl-, 3-nitro-, and 4-tert-butyl-derivatives), acetylsalicylic acid, naproxen, and iopanoic acid were chosen as model drugs. The cationics, CTAB and CPC, were found to considerably increase th< ionization constant of the weak acidS Ka ranged from-0.21 to-3.57), while the anionic, SLS, showed a negligible effect and the nonionic, Tween 80, generally decreased the ionization constants Solubility of the acids increased in aqueous micellar and in acidiLed micellar solutions. 

Imidazole or pyridine mediated silylation of l,2-0-[l-exo-ethoxy )ethylidene]-oc-D-glucopyranose failed to give a high yield of the 6-silyl ether due to some polymerization and side reactions. Activation of hydroxyl groups via a tributylstannyl intermediate followed by the tetrabutylammonium bromide catalyzed reaction with tert-butyl-chlorodiphenylsilane was more successful [231], the 6-0-silyl derivative being isolated in 87 % yield.. The lability of this protecting group under benzylation with benzyl bromide and sodium hydride at 0 °C has been observed [449]. 

It was felt that a similar alkylation reaction would allow the facile introduction of the kainoid C-3 side chain if a bromoacetate ester was used in place of allyl bromide as the alkylating agent. The aim was to attempt to increase stereoselectivity by using the bulky ester tert-butyl bromoacetate. Appropriately protected 4-keto-L-proline 39 derivatives... 

In Fig. (12) keto ester (94) was selected as starting material. It was converted to the formyl derivative (95) which yielded a,P-unsaturated aldehyde (96) by treatment with DDQ. Michael addition of the sodium enolate of tert-butyl- isovalerylacetate to aldehyde (96) afforded the adduct (97) as a mixture of C-ll diastereomers. By fractional crystallization one of the adducts could be separated but for the synthetic purpose the mixture was not separated. Treatment of the adduct (97) with p-toluenesulfonic acid in glacial acetic acid caused t-butyl ester cleavage, decarboxylation and cyclodehydration leading the formation of tricyclic enedione (98) in 80% yield. This approach was previously utilized by Meyer in the synthesis of nimbiol [29], Treatment of (98) with pyridinium bromide perbromide, followed by hydrogenolysis with palladium and carbon caused aromatization of (98) leading the formation of the phenolic ester (99). 

Most recently, Monteiro et al. have reported that cyclopalladated compounds derived from the ortho-metalation of benzylic tert-butyl thioethers are excellent catalyst precursors for the Suzuki cross-coupling reaction of aryl bromides and chlorides with phenylboronic acid under mild reaction conditions. A broad range of substrates and functional groups are tolerated in this protocol, and high catalytic activity is attained (Eq. (58)) [93]. 

This methodology still suffers from the shortcomings of salt formation and the use of bromide (10 mol%) as a cocatalyst and dichloromethane as solvent. Recently, a recyclable oligomeric TEMPO derivative, PIPO, derived from a commercially available polymer additive (Chimasorb 944) was shown to be an effective catalyst for the oxidation of alcohols with NaOCl in the absence of bromide ion using neat substrate or in e.g. methyl tert-butyl ether (MTBE) as solvent (Fig. 1.21) [71]. 

Replacement of an amino group is possible. When aniline derivatives were treated with aUyl bromide and tert-butyl nitrite (t-BuONO), the aryl-allyl coupling product was formed (Ar NH2 Ar-CH2CH=CH2). ... 

A niunber of 3-aryl- -phosphorins, 3-aryl-A --phosphorins, and 3-aryl-A -phosphorinium salts have been synthesized from oxaphosphorinium bromides (9). Spectral data indicate that in polar solvents l-chloro-3-phenyl-1-tert-butyl--A -phosphorin (10) is in equilibrium with 3-phenyl-1-fert--butyl-A -phosphorinium chloride (11). Thermolysis of derivative (10 Ph=aryl) yields the 3-aryl-A -phosphorin (12), which on oxidative alkoxylation with Hg(OAc)2/ntethanol affords the 3-aryl-1,1-dimethoxy-A -phosphorin (13) (Markl,... 

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