Methylene bromide, decomposition

Decarbonylation of cyclopropene acids. In a study of the synthesis of methyl sterculate (6) from methyl stearolate (1), Gensler et al.1 were unable to repeat the apparently straightforward synthesis based on addition of the Simmons-Smith reagent described in 1, 1021-1022. They were also unable to eifect addition of methylene generated by cuprous bromide decomposition of diazomethane. However, the reaction of (1) with diazoacetic ester in the presence of copper bronze, followed by hydrolysis, gives the cyclopropene diacid (2) in 70-90% yield. 

Methylene dichloride [6] and perchloric acid [7] were purified and dosed as described. Silver perchlorate (BDH) was treated in vacuo for a few hours before use. 1-Phenylethyl bromide (Eastman-Kodak) was fractionally distilled under high vacuum and the middle fraction was collected into breakable phials since this compound undergoes a slow decomposition, yielding hydrogen bromide and styrene, when kept in bulk, solutions of it in methylene dichloride were prepared from the original phials by the tipping technique [7]. Styrene was purified [8], dried, and stored [9] as described. Shortly before use it was vacuum-distilled into breakable phials from a microburette. 

N-NeoDentyl)-4-DihexylaminoDvrldinium Bromide (3h) The neopentyl salt was prepared in a similar manner from neopentyl mesylate, but reaction was carried out neat at 130 for 72 hr. Higher temperatures cannot be used, due to decomposition of neopentyl mesylate. The crude product was dissolved in water, basifled to neutralize any pyridinium salt, and was washed with petroleum ether to remove amine and unreacted neopentyl mesylate. The aqueous phase was acidified with HBr, and extracted with methylene chloride, to afford crude salt. Recrystallization from 20 1 ethyl acetate/acetonitrile affords the product (mp = 169-170 ). 

Arsenic tribromide dissolves in many organic liquids,15 such as carbon disulphide, methylene iodide16 and benzene in the last named the decomposition voltage is 0-50 volt.17 In solutions in diethyl ether18 the electrical conductance at 18° C. rapidly increases with increase in the bromide concentration up to 95 per cent., after which it quickly falls to... 

Freedman and Doorakian report a striking case of the use of Py+HBrj" as a mild, selective brominating agent particularly suited for compounds prone to decomposition. When the tetraphenylcyclobutadiene-nickel bromide complex (6) was treated in methylene chloride with molecular bromine, extensive decomposition occurred, and only a trace of the desired dibromocyclobutene (7) was obtained. Bromination... 

Daniel and Paetsch 40> carried out a series of labeling experiments designed to determine whether the methylene carbon atom of the ylid retains its integrity during decomposition. The ylid was labeled in several positions with 14C and 3H, but the specific ylid prepared from bromo-methyltrimethylammonium bromide and methyllithium with the methylene group labeled with 14C will be discussed here. 

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