BENZYLIC BROMINATION IN REACTIONS OF BENZYL METHYL ETHER AND RELATED COMPOUNDS WITH N-BROMOSUCCINIMIDE

Through application of nmr analysis of reaction products it has been established conclusively, as is strongly suggested by earlier work of Huang and Lee, that the benzaldehyde formed in the reaction of benzyl methyl ether and N-bromosuccinimide in carbon tetrachloride is derived mainly, if not exclusively, by breakdown of α-bromobenzyl methyl ether, the primary reaction product. The alternate reaction path in which the aldehyde is formed by direct breakdown of a radical intermediate (C6H5CHOCH3 ⟶ C6H5CHO + CH,3) is unimportant. When dibenzyl ether is substituted for benzyl methyl ether, the aldehyde is generated, in a similar fashion. No bromo ether is found in the products of reactions of benzyl t-butyl ether, but the path by which benzaldehyde forms is thought to involve the bromo ether as an intermediate. Benzyl p-chlorophenyl ether reacts to form a thermally stable α-bromo derivative and no aldehyde. Benzyl acetate is converted in part by N-bromosuccinimide into α-bromobenzyl acetate, but benzaldehyde and acetyl bromide are also formed in quantity by a process in which the bromo acetate is not an intermediate. α-Bromobenzyl methyl ether is readily hydrolyzed, but treatment of its carbon tetrachloride solution with a small amount of water results in its decomposition to benzaldehyde and methyl bromide rather than its hydrolysis. Evidence has been obtained that C6H5CH-(NC4H4O2)OR formed during the reaction of benzyl ethers (C6H5CH2OR) and N-bromosuccinimide is produced from C6H5CH(Br)OR and the brominating agent by a process which is reversible. © 1969, American Chemical Society. All rights reserved.