Xylylene bromide

T-Granate Xylyl Bromide, Benzyl Bromide, and Xylylene Bromide Mixture Cl 3-A... 

T-Stoff was a mixture of brominated aromatics including xylyl bromide, xylylene bromide and benzyl bromide. All these compounds are extreme irritants capable of severely limiting the effectiveness of unprotected troops. 

In the bromination of xylol a secondary reaction also takes place this is the conversion of xylyl bromide into xylylene bromide, due to the tendency of bromine to react with xylyl bromide as well as with the xylol also present. 

PS), ethyl bromoacetate, chloroacetane, bro-mobenzylcyanide (Agent CA), xylyl bromide, xylylene bromide, benzyl bromide, alpha-chloroacetophenone (Agent CN), O-chlorobenzylidine malononitrile (Agent CS) and dibenz(fe,/)-l,4-oxazepine (Agent CR). The latter is one of the most commonly used tear gas agents. 

Hydrolysis of optically pure bromide 100 a in dioxane/water gives the optically pure alcohol. This is consistent with the transannular p-xylylene ring participating in carbonium ion formation only through tz-g charge delocalization (iz-c resonance) of the type 104 rather than by direct participation in replacement of bromide via a transannularly bridged ion such as 102a. In the latter case, racemization would be expected to take place ... 

The formation of the heterocycle 1 from the xylylene-bis-phosphonium salt 2 and PCI3 proceeds via a detectable intermediate 3 in a cascade of condensation reactions that is terminated by spontaneous heterolysis of the last remaining P-Cl bond in a cyclic bis-ylide-substituted chlorophosphine formed (Scheme 1) [15]. The reaction scheme is applicable to an arsenic analogue of 1 [15] and to bis-phosphonio-benzophospholides with different triaryl-, aryl-alkyl- and aryl-vinyl-phosphonio groups [16, 18, 19], but failed for trialkylphosphonio-substituted cations here, insufficient acidity prohibited obviously quantitative deprotonation of the phosphonium salts, and only mixtures of products with unreacted starting materials were obtained [19]. The cations were isolated as chloride or bromide salts, but conversion of the anions by complexation with Lewis-acids or metathesis was easily feasible [16, 18, 19] and even salts with organometallic anions ([Co(CO)4] , [CpM(CO)3] (M=Mo, W) were accessible [20]. 

Another annellation reaction starts from a,a -dibromo-o-xylene, an activated olefin and zinc.63 This reaction, according to the authors proceeds by a Diels-Alder cycloaddition via the o-xylylene (Scheme 15.10), and was employed in carbohydrate chemistry to prepare anthracyclinones analogues.64 No reaction occurs without sonication. Instead of a cycloaddition, another explanation can be postulated, consisting first of addition of a mono-organozinc reagent to the activated olefin, followed by alkylation of the resulting enolate by the second benzylic bromide. 

Acenaphthylene dibromide (147) was also reduced to produce acenaphthylene (148) in quantitative yield (equation 85). A similar result was reported by Inesi and collaborators129, and confirmed again by others130. Four-electron reduction of ortho-xylylene tetra-bromide (149) gives the same stable product, 146, deduced to arise from benzocyclo-butadiene following a [4+2] cycloaddition and retro[2+2] rearrangement to rearomatize. 

More rational syntheses of related fiiran-containing systems involve the condensation of bis-ylides with bis-aldehydes. The simplest such approach involved the condensation of 2,5-diformylfiiran (169) with o-xylylene-bis[triphenylphosphonium bromide] (170) under basic conditions. The result was the production of three isomers of the formal 2 + 2 condensation product (Scheme 27) [146]. Irradiation of the three isomers 171-173 gave a single new isomer 174. Compound 174 may also be generated by the reaction of the bis-ylide 170 with 175 (Scheme 28) [147]. 

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