4- Bromobenzyl bromide

Bromobenzyl 2-fluorophenyl thioether, derived from 2-fluorothiophenol and 2-bromobenzyl bromide, is a source of a benzyne through reaction with /-butyllithium. Simultaneously, the bromobenzyl moiety generates the tethered aryllithium 405 and an intramolecular anionic cyclisation is promoted. The sequence is completed by the addition of an electrophilic species leading to 1-substituted b/Z-dibenzol //]thiopyrans (Scheme 121) <2002CEJ2034>. 

Early examples of intramolecular aryl radical addition reactions to heteroatom containing multiple bonds included cyclizations on N=N and C=S moieties [52, 53]. Recently, cyclizations to imines have been used as part of a new enantio-selective approach to indolines (Scheme 8). In the first step of the sequence, the required ketimines 19 were obtained by phase-transfer catalyzed alkylation of 2-bromobenzyl bromides 20 with glycinyl imines 21 in the presence of a cincho-nidinium salt [54], Due to the favorable substitution pattern on the imine moiety of 19, the tributyltin hydride mediated radical cyclization to 22 occurred exclusively in the 5-exo mode. The indoline synthesis can therefore also be classified as a radical amination. 

Several extensions of this approach have been attempted, but none was successful. Only a faint odor results from the attempted synthesis of cyclopropa[Z)]naphthalene and none of the expected cyclopropa[a]naphthalene or cyclopropa[/]phenanthrene were generated in the corresponding reactions.- The same difficulties have been experienced with other benzyl derivatives. The reaction of 2-bromobenzyl bromide, 2-bromobenzyl chloride and 2-iodobenzyl bromide with butyllithium gave (partially) reduced bibenzyls or 9,10-dihydroanthracene, but no benzocyclopropene. Similarly, lithiation of 2-bromobcnzylsulfonates afforded only trace amounts (< 5%) of bcnzocyclopropene, while only methoxymethylbenzene was isolated on treatment of l-methoxymethyl-2-trimethylsiIylbenzene with fluoride ions. ... 

The preparative interest in the halogen addition to cycloproparenes is very limited, but it has been used occasionally as a diagnostic test. When the reaction of benzocyclopropene with iodine was carried out in carbon tetrachloride at 25 C, rather than under photochemical conditions, 1,6-diidocyclohepta-l, 3,5-triene was formed in only 6% yield, while cleavage to 2-iodo-benzyl iodide (la, 85%) predominated. With bromine benzocyclopropene reacted exclusively to give 2-bromobenzyl bromide (lb, 98%). The same type of reaction prevailed with iodine and 1,1-difluorobenzocyclopropene in refluxing carbon tetrachloride for 48 hours giving l-(difluoroiodomethyl)-2-iodobenzene in poor yield (9%), which was only partially characterized. The reaction between 1,1-difluorobenzocyclopropene and bromine is discussed in Section 2.1. 

In another report, 1,5-benzodiazepines have been obtained from reaction of alk-3-yn-l-ones with 1,2-phenylenediamines in ethanol under microwave heating without the need for any catalyst (14GC1120). A palladium-catalyzed domino reaction between 1,2-phenylenediamines and 10,11-dihydro-5H-dibenzo[fc,e][l,4]diazepines starting from 2-bromobenzyl bromides has also been developed (14EJ04773). 

In a substrate-dependent, palladium-catalyzed domino N-benzylation/ intramolecular direct arylation process, tosylamides 133 and 2-bromobenzyl bromides 134 reacted to form dibenzo-l,2-thiazepine dioxides 135 exclusively, or gave mixtures that also contained 6,7-dihydro-5H-dibenzo[c,e] azepines 136 (14JOC10899). 

FLUORINECOMPOUNDS, ORGANIC - FLUORINATED AROMATIC COMPOUNDS] (Volll) p-Bromobenzyl bromide [589-15-1]... 

Bromobenzaldehyde has been prepared by the oxidation of -bromotoluene with chromyl chloride/ by saponification of the acetal from />-bromophenylmagnesium bromide and orthoformic ester/ by the oxidation of ethyl -bromobenzyl ether with nitric acid/ by the oxidation of /j-bromobenzyl bromide with lead nitrate/ and by the hydrolysis of i-bromobenzal bromide in the presence of calcium carbonate. ... 

Buchwald parlayed the powerful Buchwald-Hartwig aryl amination technology [439-447] into a simple and versatile indoline synthesis [448-452], For example, indole 368, which has been employed in total syntheses of the marine alkaloids makaluvamine C and damirones A and B, was readily forged via the Pd-mediated cyclization shown below [448], This intramolecular amination is applicable to the synthesis of -substituted optically active indolines [450], and o-bromobenzylic bromides can be utilized in this methodology, as illustrated for the preparation of 369 [451]. Furthermore, this Pd-catalyzed amination reaction has been applied to the synthesis of arylhydrazones, which are substrates for the Fischer indole synthesis [453,454],... 

With both enantiomers of le in hand, the asymmetric synthesis of (S)-N-acetylindoline-2-carboxylate 33 was carried out, this being a key intermediate in the synthesis of the angiotensin-converting enzyme (ACE) inhibitor 34 (Scheme 5.18) [7e], The structure and stereochemical integrity of 33 was simultaneously constructed by the asymmetric alkylation of 2 with o-bromobenzyl bromide in the presence of (R,R)-le, and subsequent hydrolysis and N-acetylation afforded 32 in 86% yield with 99% ee. According to the Buchwald procedure, almost enantiopure 32 was efficiently converted to 33 (94%, 99% ee) [7e],... 

V3 HN ° NH o-bromobenzyl bromide Ag20 v° HN ° NL X) benzyl bromide K2CO3... 

Dibromobibenzyl has been prepared by the bromination of bibenzyl in water 9 by the reaction of />-bromobenzyl bromide with zinc dust in water 10 and by the reaction of bromobenzene with ethylene oxide in the presence of anhydrous aluminum chloride.11... 

The key synthetic steps in the formation of the desired unnatural amino acids, 5-8, involved the preparation of appropriately substituted cyclobutanones followed by a Btlcherer-Strecker amino acid synthesis.12 The syntheses of the boron-containing amino acids were initiated utlizing alkenes 16 -19. Alkene 17 was prepared by a SN2 displacement of bromide from 4-bromobenzyl bromide (Scheme 3). In the syntheses of alkenes 18 and 19, a catalytic... 

C7H6Br2 3-bromobenzyl bromide 823-78-9 515.15 45.342 2 10297 C7H6FN02 2-amino-6-fluorobenzoic acid 434-76-4 496.82 43.578 2... 

By the action of bromine in the presence of iodine, /)-bromobenzyl chloride and />-bromobenzyl bromide are formed. ... 

II. The benzocyclobutene derivative can be prepared by direct reaction of o-bromobenzyl bromide with RgSiCla in the presence of magnesium 108, 129). The small membered ring system has also been synthesized by ring closure with formation of one ring bond ... 

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