Octane 1,8-dibromo

Thermal rearrangement of trans-l,2-dibromo compounds is known in the literature (refs. 6-10). In all case studies only one pair of bromine in each organic molecular was studied. Bellucci (ref. 10), for example, studied the kinetics of such trans-l,2-cyclo alkanes as cyclopentane, hexane, octane, etc. The intermediates suggested as an explanation for the experimental results are bromonium bromide I in polar solvents and four center transition state II in non-polar solvents. 

A bicyclic peroxide was isolated in 1.8% yield by HPLC of the bromodemercuration product, and was identified as a single diastereoisomer of 2,4-dibromo-6,7-dioxa-bicyclo[3,2.1]octane 57 with the iransjrans- or cis,cis-configuration. By analogy with the cyclooctadiene reactions, formation of the other two diastereoisomers of 57 can be expected, but although additional peroxides with similar HPLC characteristics were detected, they were not identified. Thus the presence of [2.2.2]-compounds cannot be ruled out, and no comment can be made on the regioselectivity of the dioxabicyclization. 

The power of the HR-MAS method for on-resin analysis has been further underscored in the development of new linkers. Without this method, only indirect analytical data after removal from the resin was available. Direct assessment of the resin-bound linker greatly facilitated the introduction of a 4,5-dibromo octane- 1,8-diol linker that was converted into an octane-1,8-diol linker cleavable by olefin metathesis at the end of the synthesis.6 The disappearance and reappearance of the olefinic protons as well as the growing oligosaccharide chain was clearly visible in the H spectrum (Fig. 8.7).7... 

A series of polyphosphites, polyphosphates, polythiophosphates, and other polymers containing sulfone functions, based on 1, have also been described [17,119]. An efficient synthesis of polyethers from 1 and 1,8-dibromo or dimesyl octane by microwave-assisted phase transfer catalysis has been reported [120]. 

The main steps in the currently accepted catalytic cycle of the Heck reaction are oxidative addition, carbopalla-dation (G=G insertion), and / -hydride elimination. It is well established that both, the insertion as well as the elimination step, are m-stereospecific. Only in some cases has formal /r/ / i--elimination been observed. For example, exposure of the l,3-dibromo-4-(dihydronaphthyloxy)benzene derivative 16 and an alkene 1-R to a palladium source in the presence of a base led to a sequential intra-intermolecular twofold Heck reaction furnishing the alkenylated tetracyclic products 17 in good to excellent yields (Scheme 9). " In the rate-determining step, the base removes a proton in an antiperiplanar orientation from the benzylic palladium intermediate. The best amine base was found to be l,4-diazabicyclo[2.2.2]octane, which apparently has an optimal shape for this proton abstraction. 

The reduction of l-alkyl-8,8-dibromo-bicyclo[5.1.0]octanes by methyl magne-siumbromide in tetrahydrofuran provides mixtures of fully and partially reduced products [31], A comparable result is obtained when zinc in dimethylformamide... 

That the allene route should always be kept in mind, though, is demonstrated for example by 6,6-dibromobicyclo[3.1. OJoctane and 8,8-dibromo-bicyclo[5.1.0]-octane, respectively. When these bicyclic dibromides are reacted with methyl-lithium at room temperature they are evidently converted into the corresponding cyclic allenes since these intermediates may be either trapped by reagents like styrene or dimerize, [2+2]adducts being formed in both cases. 

Dibromo-5,6-epoxy-7,8-dioxabicyclo[2.2.2]octane, 2291 2,3 5,6-Diepoxy-7,8-dioxabicyclo[2.2.2]octane, 2332... 

Treatment of l,3-dibromo-3,5-dibromomethyladamantane with zinc results in a double fragmentation of the adamantane ring 1,3,5,7-tetramethylenecyclo-octane is formed in high yield. Bromination of the product with bromine in carbon tetrachloride regenerates the starting material 3631. 

The telluretane derivative 3,5-dibromo-8-telluratricyclo[2.2.1.1]octane 8,8-dibromide was prepared from tellurium tetrabromide and bicyclo[2.2.1]-2,5-heptadiene (norbomadiene)4. 

Dibromo-8-telluratricyclo[2.2.1.1]octane 8,8-Dibromide4 1.84 g (20 mmol) of norbomadiene are dissolved in 150 ml of diethyl ether and the solution is cooled to 0°. 3.20 g (20 mmol) of tellurium tetrabromide are dissolved in 20 ml of concentrated hydrobromic acid and added dropwise to the stirred norbomadiene solution. The mixture is stirred for 4 h, the organic phase is separated, dried with anhydrous magnesium sulfate, and evaporated yield 1.02 g (9.5%) in.p. 116°. 

Morpholinocyclopentene has been used to elaborate bicyclo[3.3.0]octane derivatives through cycloaddition to cyanoallene220- and the reagent produced from 2,4-dibromo-3-pentanone and diiron ennacarbonyl.221 ... 

What is the stereochemical configuration of the enantiomer of (2S,4R)-dibromo-octane ... 

Reductive dehalogenation with tin hydrides can be carried out without interference of a number of functional groups. However, a C-C double bond in a 1,5 relationship to the intermediate cyelopropyl radical can function as a trap and result in formation of bicyclo[3.1.0]hexane derivatives. Thus, treatment of l,l-dibromo-2-(but-3-enyl)cyclopropane with tributyltin hydride afforded a 15 85 mixture of l-bromo-2-(but-3-enyl)cyclopropane (13) and 1-bromo-2-methyl-bicyclo[3.1.0]hexane (12). Under similar conditions l-bromo-2,8,8-trimethyltricyclo-[3.2.1.0 ]octan-3-one (15) was obtained in 6% yield from an isomeric mixture of 7,7-dibromo-4-isopropenyl-l-methylbicyclo[4.1.0]hept-2-one the main product, isolated in 86% yield, was an isomerie mixture of 7-bromo-4-isopropenyl-l-methylbicyclo[4.1.0]hept-2-one (14). ... 

Fluoride-ion promoted elimination of /J-halosilylcyclopropanes has also been utilized to prepare Diels-Alder adducts from less strained cyclopropene intermediates. Thus, when 1,1 -dibromo-2-trimethylsilylcyclopropane was reacted with potassium fluoride in diglyme containing 1,3-diphenylisobenzofuran, ( nc o-2-bromo-l,5-diphenyl-8-oxabenzo[/]bicyclo[3.2.1.0 ]octane (5) was obtained in 77% yield.Other examples can be found in refs 92,254, 347, 722, 728-737, 942. 

Dibromo-, 8,8-dichloro- and exo-8-bromobicyclo[5.1.0]octane 24a-c were converted by silver(I) perchlorate in methanolic solution to the corresponding trani-cyclooctenols 25, in high yield. In all cases the product consists only of the one indicated stereoisomer. 2-Iodo-and 2-alkyl-substituted tro 5-cycloalkenes have been prepared analogously. ... 

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