Tribromomethylation

Bromination of quinaldine (I) (Section V,2) with bromine in glacial acetic acid in the presence of anhydrous sodium acetate aflFords dilute sulphuric acid gives quinaltiinic acid (III). 

The adducts containing di- and tribromomethyl groups can react with another molecule of monomer, i.e. the secondary reactions occur including step-by-step telomerization in this case. The presence of the bromine atom adjacent to the radical center makes it probable the fragmentation with ejection of the bromine atom, which starts the further reaction, and as a result, the products of bromine addition to a double bond, not adducts, are formed. 

Similarly, the ratio of dibromocarbene addition to CBr. substitution in the reaction of propyl bromide with tribromomethyl can be varied between 92 1 and 1 91, depending on whether a small and accessible quat or a bulky anion-activating quat is used (Dehmlow and... 

Triphenylmethane leuco dyes are used for photographic materials. The photographic system requires a polymer binder such as acrylic acid-methyl methacrylate copolymer115 or a copolymer of isophthalic and terephthalic acids116 a sensitizer such as 4-(4-n-amyloxyphenyl)-2,6-bis(3-ethylphenyl)-thiapyrilium perchlorate,117 a photo initiator such as hexaarylbisimi-dazole,118 and phenyl tribromomethyl sulfone, cycloalkane such as 1,2,3, 4,5-pentabromo-6-chlorocyclohexane,119 or 3-benzylidene-9-methyl-2,3-dihydro- 1 TZ-cyclopenta [b] quinoline.120... 

Interaction to form the corresponding tribromomethyl compound is extremely hazardous, even using previously specified precautions [1]. Several fires occurred in the effluent gases, and in reaction residues exposed to air [2], doubtless owing to phosphine or its derivatives. 

The reaction of nitrones of the 3-imidazoline series (295) with bromine and amyl nitrite, in the presence of base, gives a-tribromomethyl-(296) and a-hydroxyaminomethyl derivatives (297) (538). Bromination of nitrones (295) with N -bromosuccinimide (NBS) in CCI4 or bromine in methanol leads to the formation of a-bromoalkyl (298 a,b, Hal = Br) and a-dibromomethyl (299) nitrones (539-541). The reaction with iodine in methanol gives the mono iodo derivative (300) (541). The reaction with A-chlorosuccinimide (NCS) in CCI4 leads to a-chloroethyl nitrones (298b, Hal = Cl) and a,a-dichloromethyl nitrones (301) (Scheme 2.118) (225). 

While the haloform reaction normally only cleaves methyl ketones because of the structural requirements for the a,a,a-tribromomethyl ketone to induce fragmentation, the strain release that accompanies cleavage of a cyclobutanone permits extension... 

Bromine trifluoride, neat or dissolved in liquid bromine, has found application for the selective substitution of fluorine for bromine (Table 3).108,109 The reactions are carried out at temperatures of no more than 60 C. Under these conditions no hydrogen substitution is observed. As established for bromofluoroethanes. the relative ease of replacement of bromine in various groups decreases in the order tribromomethyl > dibromofluoromethyl > dibromomethyl > bromofluoromethyl > bromomethyl. The presence of fluorine at either the same or an adjacent carbon tends to retard the substitution. Bromine trifluoride is more effeetive than antimony fluorides as it replaces bromine in bromodifluoromethyl and bromomethyl groups. 

Several reactions of 2-methyl-1,10-phenanthroline have been reported. It is readily brominated to the 2-tribromomethyl derivative, which affords 2-carboxy-1,10-phenanthroline on hydrolysis.356 2-Methyl-... 

Silver ion-promoted ring enlargement of the l-tribromomethyl-l,2-dihydroisoquinoline 334 (prepared from 333, which was accessed in turn from isoquinoline) resulted in a compact approach to the 3-benzazepin-2-ones 335 (Scheme 44) <2003TL4203>. 

TV-Benzoyl esters 372 and 374 undergo dihalocarbene addition with phenyl (tribromomethyl)mercury 371 to yield adducts 373 and 375, respectively [381] (Scheme 3.121). But A-methyl- and A-benzyl-substituted analogues of 372 and... 

Attempts to brominate the free amine (148) were disappointing (Scheme 3.28). Either incomplete reaction was observed or else a mixture of mono-, di- and tribrominated compounds was obtained. Nonetheless, treatment of this crude mixture with p - am i n o b en z oy lglutam ic acid generated the amide (149), which presumably resulted from bromide displacement in the tribromomethyl precursor, followed by hydrolysis of the remaining geminal dibromide during work-up. 

A similar change in orientation of attack arises with the fluorobromomethyl radicals where the bulkier the radical, the lower the relative rate of attack at the most substituted end of an unsymmetric olefin (Table 13). This increase in selectivity is believed to be primarily due to steric effects. Lone pair repulsion is unlikely to be important in the tribromomethyl radical, and bromine is less electronegative than fluorine. 

The above obtained [(4S)-4-Methyl-5-oxo-2-(tribromomethyl)-l,3-dioxolan-4-yl]acetic acid (102.5 mg 0.250 mmol) and 2-mercaptopyridine- N-oxide (34.4 mg 0.280 mmol) were suspended in CBrCI3 (1.5ml). The reaction mixture was heated to reflux and a solution of dicyclohexyl carbodiimide (DCC) (103 mg 0.500 mmol) in CBrCI3 (1.0 ml) was added slowly over the course of 30 min. The reaction mixture was stirred for an additional hour. The product was purified by silica gel chromatography (CH2CI2/hexanes (1 2)) and was obtained as white needles from the same solvents. Yield 72 mg (65%) mp 110-113°C. 

This combination reaction is very sensitive to the temperature conditions. We encountered complications when using phenyl (tribromomethyl)-mercury since mixtures of olefins arose. 

In the early 1990s, Fuji Photofilm Ltd. Introduced Copiart 3 proofing materials, which also depended on HABI chemistry. The chemistry used the lower cost o-Cl-HABI and Leuco Crystal Violet along with tribromomethyl phenyl sulfone, which were microencapsulated in selected vehicles. The image stabilization was achieved by a thermal aftertreatment, which ruptured the microcapsules, which then interacted with phenidone, or other reducing agents to prevent subsequent color formation. 

A blue tetrabromo derivative has also been prepared [65JCS3785 76JCS(P1)2353]. Nuclear magnetic resonance spectra showed that this is the 2,4-bis(dibromomethyl)benzodiazepinium bromide a corresponding hexabromo derivative was obtained by bromination of 7,8-dibromo-2,4-dimethyldihydrodiazepine [76JCS(P1)2353]. When either of these polybromo derivatives was treated with excess bromine in acetic acid, yellow products were obtained that, from analysis and NMR spectra, appeared to be 3,7,8-tribromo-2,4-bis(tribromomethyl)-3//-benzodiazepine.This can be reduced catalytically to give 7,8-dibromo-2,4-bis(dibromomethyl)benzodiazepine [76JCS(P1)2353],... 

Transbromination of ketones and activated aromatic compounds (phenols, naphthols, indole) by 4-(tribromomethyl)quinazoline is catalyzed by TFA245. Alkanes are brominat-ed by complexes of bromoform with aluminum tribromide (equation 33)246. 

This method is an alternative to the former method in which sodium hypochlorite or t-butyl hypochlorite have been used in -butanol, or under PTC for the same purpose623. The analogous tribromomethyl derivative is prepared from the dibromomethyl compound by reaction with sodium hypobromite624. 

Thus cyclopentene reacts with tribromomethyl phenyl sulfone to give a high yield of addition product (equation 106). Samarium iodide catalysis gives a good yield of addition product upon reaction of l-chloro-2-iodoethanes with 1-alkenes (equation 107)690. The product from this reaction has been used to prepare a cyclic target molecule in several further steps. a-Bromoesters also undergo a similar reaction, the product from which upon treatment with KOH gives lactones directly. 

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