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Silver, Howard Bernard (1956) Interaction of boron trichloride with unsaturated alcohols and ethers. Doctoral thesis, Northern Polytechnic.
An investigation has been carried out on the interactions between boron trichloride and unsaturated alcohols and ethers. The properties of certain trialkenyl borates (RO)3B, dialkenyl chloroboronates (RO)2BCl, and alkenyl dichloroboronites (RO)BC12, have been studied. From this work, results have been obtained which are of interest in organoboron chemistry and in general organic chemistry.
The borates were prepared from the alcohol and either boron trichloride or boric acid. The chloroesters of but-3-en-1-ol were sufficiently stable to be distilled, but those of allyl alcohol and 2-methylallyl alcohol had to be characterised as the pyridine complex; these complexes undergo subsequent disproportionation. The chloroesters of 1- and 3-methylallyl alcohol were unstable even at -80°, so pyridine complexes of these were not identified.
Tri alkenyl borates reacted only slowly with hydrogen chloride, but were more reactive towards hydrogen bromide and hydrogen iodide, addition and dealkenylation occurring simultaneously. Triallyl borate could not be estimated by means of the Br2/carbon tetrachloride method, but a concentrated solution of bromine was found to react with the double bond. From the stabilities of the chloroestersand of their pyridine complexes, and from the dealkenylation of boratec and the mode of formation of the borates, infomation concerning the relative electron-release of the alkenyl groups was obtained.
By studying the interaction of alkyl allyl ethers with boron trichloride, the relative electron-release of the allyl group has been established. Allyl phenyl ether, when allowed to react with boron trichloride, underwent the Claisen rearrangement, ortho-allylphenol and its borate being isolated.
Results in the 1- end 3-methylallyl systems support previously proposed mechanisms for the decomposition of alkyl chloroesters, and the dealkylation of the borates. From the results found, it was evident that the butenyl chloride obtained from the 1- and 3-methylallyl systems, contained in each case the same mixture of 1- and 3- methylallyl chloride, thereby Indicated SN1' mechanisms. Alcoholysis of the 1- and 3-methylallyl borate afforded 1-methylallyl alcohol in the fomer systems and 8.7% 1-methylallyl alcohol, 91.3% 3-methylallyl alcohol from the latter. Hydrolysis afforded the unchanged alcohol in both systems.
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