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Please login to access the full content or check if you have access via Variation 2: Chloromethylation with Formaldehyde and Hydrogen Chloride

DOI: 10.1055/sos-SD-035-00163

Pfeiffer, W. D.Science of Synthesis, (200735158.

An aqueous solution of formaldehyde can also be used for the chloromethylation of arenes. The treatment of benzene with formaldehyde, hydrogen chloride gas, and zinc(II) chloride affords benzyl chloride in 76% yield.[‌28‌] The chloromethylation of 1,3,5-trimethylbenzene with a 37% formaldehyde solution leads to 2-(chloromethyl)-1,3,5-trimethylbenzene (5566%).[‌29‌] 1,2,3,4-Tetramethylbenzene (9) reacts with aqueous formaldehydehydrogen chloride to give 1-(chloromethyl)-2,3,4,5-tetramethylbenzene (10) (Scheme 6).[‌30‌] 1-(Chloromethyl)-2,3,4,5,6-pentamethylbenzene is obtained from 1,2,3,4,5-pentamethylbenzene with 37% formaldehyde solution and hydrogen chloride.[‌30‌] The reaction of naphthalene with 30% aqueous formaldehyde gives 1-(chloromethyl)naphthalene.[‌6‌] A mixture of 40% aqueous formaldehydehydrogen chloride reacts with phenanthrene to give 9-(chloromethyl)phenanthrene.[‌31‌] Treatment of thiophene with aqueous formaldehydehydrogen chloride affords 2-(chloromethyl)thiophene[‌32‌‌35‌] {see also Science of Synthesis, Vol.9 [Fully Unsaturated Small-Ring Heterocycles and Monocyclic Five-Membered Hetarenes with One Heteroatom (Section]}. Thiophene reacts with an excess of 37% formaldehyde solution to give 2,5-bis(chloromethyl)thiophene.[‌36‌] Treatment of uracil with 38% aqueous formaldehydehydrogen chloride affords 5-(chloromethyl)uracil in 45% yield.[‌37‌]

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