Bromocyclopropane

Submitted by John S. Meek and David T. Osuga.1 Checked by F. S. Fawcett and B. C. McKusicc. 

Twenty-four grams (0.11 mole) of red mercuric oxide (Note 1) and 60 ml. of freshly distilled 1,1,2,2-tetrachloroethane are placed in a 250-ml. three-necked flask equipped with a dropping funnel, a reflux condenser, and a stirrer. A solution of 32.2 g. (0.20 mole) of bromine and 17.2 g. (0.20 mole) of cyclopropanecarboxylic acid in SO ml. of tetrachloroethane is added dropwise to the stirred suspension of mercuric oxide over a period of 45 minutes, the flask being kept in a water bath at 30-35° (Note 2). The mixture is stirred after the addition of the reactants until the evolution of carbon dioxide ceases. 

The flask is then cooled in ice water, and the contents are filtered with as little suction as possible (Note 3). The filter cake is pressed dry and washed with three 15-ml. portions of tetrachloroethane first used to rinse out the flask. The combined filtrates are dried with a little calcium chloride. Sometimes the solution contains a little bromine it is removed by adding allyl alcohol dropwise until the bromine color is discharged (usually 0.5-1.0 ml. suffices). 

The solution is decanted into a 200-ml. round-bottomed flask 

The reaction starts spontaneously and is mildly exothermic. Moderating the temperature by use of a water bath diminishes the amount of bromine and product carried off by the carbon dioxide evolved. The reaction can be followed by use of a tetra-chloroethane bubbler, and at the end of the reaction the solvent in the bubbler can be used to wash the mercuric bromide. The checkers followed the reaction with a wet test meter presaturated with carbon dioxide 52-60% of the theoretical amount of carbon dioxide was evolved. 

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Bromocyclopropane has been prepared by the Hunsdiecker reaction by adding silver cyclopropanecarboxylate to bromine in dichlorodifluoromethane at —29° (53% yield) or in tetrachloro-ethane at —20° to —25° (15-20% yield).3 Decomposition of the peroxide of cyclopropanecarboxylic acid in the presence of carbon tetrabromide gave bromocyclopropane in 43% yield.4 An attempt to prepare the bromide via the von Braun reaction was unsuccessful.3... 

Cyclopentene-l,2-diol, 42, 51 2-Cyclopentene-1,4-dione, 42, 36 2-Cycloeentene-1-one, 42, 38 2-Cycloeentenone, 42,38 Cyclopropane, bromo-, 43, 9 Cyclopropanecarboxylic add, conversion to bromocyclopropane, 43, 9... 

Bromo- and iodocyclopropanes cannot be prepared by the direct halogenation of cyclopropanes. Substituted chloro- and bromocyclopropanes have been synthesized by the photochemical decomposition of a-halodiazomethanes in the presence of olefins iodocyclopropanes have been prepared from the reaction of an olefin, iodoform and potassium f-butoxide followed by the reduction of diiodocyclopropane formed with tri-w-butyl tin hydride. The method described employs a readily available light source and common laboratory equipment, and is relatively safe to carry out. The method is adaptable for the preparation of bromo- and chlorocyclopropanes as well by using bromodiiodomethane or chlorodiiodomethane instead of iodoform. If the olefin used will give two isomeric halocyclopropanes, the isomers are usually separable by chromatography. ... 

This reaction has been successfully applied to cyclopentenone annelation onto cycloalkenes. By modifying Danheiser s protocol [15], alkynyl-substituted bi-cyclo[n.l.0]alkanol derivatives are prepared by the reaction of gem-lithio-bromocyclopropanes 27 with alkynylborons, as shown in Scheme 10. 

Tributyltin hydride reduces selectively bromocyclopropanes without affecting the triple bond (equation 167)231. The reduction of gem-dibromides is stepwise, which enables convenient access to the monobromoacetylenes and further, via elimination of HBr, to 3-(cyclopropylethynyl)cyclopropene. 

It is found that bromodiazirine A undergoes loss of bromide to produce a cation much more easily than bromocyclopropane C. Can you think of a reason why ... 

Analogously to carbene 248, bromo(trimethylsilyl)carbene 250 was generated by thermal decomposition of an equimolar mixture of 249 and Pt Hg (equation 84) and transferred to cyclohexene75. Although the a-cli mi nation reaction of the carbene precursor occurs faster than in the chloro case, the obtained bromocyclopropane is less stable under the still harsh reaction conditions and is partly decomposed. 

Cleavage-cationic cyclization of bromocyclopropanes. Bromocyclopropanes sub-st i tuted by a suitably situated hydroxyl or carboxyl group undergo cleavage-cyclization at 25° in the presence of 1-1.5 equiv. of AgOCOCF3 or Hg(OAc)2. Vinyl lactones, tetrahydropyranes, or tetrahydrofuranes can be prepared in this way.1... 

Besides by these epoxidations, oxaspiropentanes have been prepared through the nucleophilic addition of 1-lithio- 1-bromocyclopropanes to ketones at low temperature. Thus for example, the dibromocyclopropane 96 prepared by addition of dibromo-carbene to cyclohexene 52) underwent metalation with butyllithium to give the lithio-bromocyclopropane 97 which was converted into the oxaspiropentane 98 upon simple addition to cyclohexanone, Eq. (28) 53,54). 

While the nucleophilic addition of 1-lithio-l-bromocyclopropanes to ketones gave oxaspiropentanes, precursors of 1-donor substited vinylcyclopropane derivatives vide supra, Sect. 4.5, Eq. (28)), addition of n-BuLi at low temperature to 1,1-di-bromocyclopropane 199 (prepared in 75 % yield from the addition of dibromocarbene... 

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