A Green Route to Benzyl Phenyl Sulfide from Thioanisole and Benzyl Alcohol over Dual Functional Ionic Liquids

Abstract

Benzyl phenyl sulfide is a kind of important chemicals with wide usage, which is mainly prepared through a nucleophilic reaction of thiophenol with benzyl chlorides or benzyl alcohols, suffering from inherent drawbacks, such as low efficiency, requirements for equivalent acid or base catalysts and formation of harmful byproducts and waste. Herein, we report a green route to access various benzyl phenyl sulfide derivatives in good to excellent yields under mild conditions via the reaction of thioanisoles with benzyl alcohols over ionic liquid 1-propylsulfonate-3-meth-ylimidazolium trifluoromethanesulfonate ([SO 3 HPrMIm][OTf]). Mechanism investigation indicates that the synergic effect of cation and anion of [SO 3 HPrMIm][OTf] activates thioanisoles and benzyl alcohols via hydrogen bonding, thus catalyzes the dehydration of benzyl alcohol to dibenzyl ether and the subsequent metathesis reaction between dibenzyl ether and benzyl phenyl sulfide, finally generating benzyl phenyl sulfide derivatives. This is a simple, highly efficient, and green approach to produce benzyl phenyl sulfide derivatives, which has promising application potentials.

A Bioinspired C–O/C–X σ-Bond Metathesis

“…The metathesis of the C-S bond for the synthesis of more complicated homologs was only possible with transition metal catalysis that relies on ligand exchange with a second thiolate [15][16] or with the formation of a highly reactive aryne intermediate 32 or over an inoinc liquid. 33 To our delight, under the optimized reaction condition, simple aliphatic alcohols (4a-4d), alcohol bearing a phthalimide moiety (4e), and aromatic alcohols (4f-4h) can react with commercially available methyl phenyl thioether to give the alkyl transposition product, which is usually cumbersome to obtain with previous methods. A substrate scope study with 2-phenyl alcohol showed that various substituents, including alkyl (4i), electron-withdrawing (4j), electron-donating (4k), as well as halogens (4l-4p) on the aromatic thioethers are all well tolerated.…”

“…2). 33 Although 1a-2 and 1a-3 were not detected in the reaction mixture when 1a-2 was submitted to the standard reaction condition, a reduced yield of 3a was obtained and no 3a in the absence of ZnI 2 (Eq. 3), in contrast, 1a-3 gave higher a yield of 3a in the absence of ZnI 2 while its presence depressed the reaction (Eq.…”