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Task-Specific Ionic Liquids
Published in Pedro Lozano, Sustainable Catalysis in Ionic Liquids, 2018
Swern oxidation is most powerful method of converting almost every type of alcohol into corresponding carbonyl compounds quantitatively under milder conditions. However, Swern oxidation involves use of sulphur compounds which are difficult to handle due to their toxicity and pungent smell. Chan et al. developed a sulfide-based task ionic liquid clean and odorless method for Swern oxidation, Figure 1.22 [44].
A novel practical preparation of methyl methanethiosulfonate from dimethyl sulfoxide initiated by a catalytic amount of (COCl)2 or anhydrous HCl
Published in Journal of Sulfur Chemistry, 2021
Shuai Huang, Hao Wang, Yongguo Liu, Baoguo Sun, Hongyu Tian, Sen Liang
From above results, methanesulfenic acid (1) is proposed to be formed initially as the key precursor for MMTS formation (Scheme 2). It is well known that the reaction of DMSO with (COCl)2 rapidly generates chlorodimethylsulfonium salt (2) as an intermediate, which is the key active species in Swern oxidation. DMSO attacks the methyl group of chlorodimethylsulfonium salt via nucleophilic substitution leading to the formation of methanesulfenyl chloride and methoxydimethylsulfonium salt (3), which was reported by Bellesia et al [44] and also observed in our previous work [34]. The methoxydimethylsulfonium salt (3) further decomposes to dimethyl sulfide, formaldehyde, and a proton (H+). The transfer of this proton to DMSO produces hydroxydimethylsulfonium salt (4), which is subsequently attacked by DMSO on the methyl group via nucleophilic substitution to regenerate methoxydimethylsulfonium salt (3) and release methanesulfenic acid (CH3SOH, 1). In our previous work, formaldehyde formed in this regeneration cycle of methoxydimethylsulfonium salt (3) was utilized for the preparation of N-acylbenzoxazines from phenols and nitriles [45].