Efficient and/or selective methylation by diazomethane of alcohols, halo alcohols, glycols, amino alcohols and mercapto alcohols with the use of a proton‐exchanged X‐type zeolite as an acid–base bifunctional catalyst

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<jats:title>Abstract</jats:title><jats:p>Reactions of diazomethane with butanol, allyl alcohol and β‐ and γ‐halo alcohols led to efficient methylation (giving the corresponding methyl ethers) with the use of a proton‐exchanged X‐type zeolite compared with H<jats:sub>2</jats:sub>SO<jats:sub>4</jats:sub>. The reactions with propylene and isobutylene glycols using the zeolite provided regioselective methylation of the primary OH rather than the secondary or tertiary OH, whereas regioselectivity was not observed in the reactions using H<jats:sub>2</jats:sub>SO<jats:sub>4</jats:sub>. The reactions with 2‐aminoethanol and 2‐mercaptoethanol showed high chemoselective <jats:italic>S</jats:italic>‐methylation and <jats:italic>N</jats:italic>‐monomethylation, respectively, in the presence of the zeolite instead of H<jats:sub>2</jats:sub>SO<jats:sub>4</jats:sub>. The mechanism for the reactions is proposed to involve acid–base bifunctional catalysis of the zeolite in which the acidic site reacts with diazomethane to form its conjugate acid, and the nucleophilicity of OH and SH groups is enhanced by the interaction of the basic site with the proton of the groups.</jats:p>

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