Dimethyl Sulfoxide-Trifluoroacetic Anhydride

Abstract

(DMSO) [67-68-5] C2H6OS (MW 78.13) InChI = 1S/C2H6OS/c1-4(2)3/h1-2H3 InChIKey = IAZDPXIOMUYVGZ-UHFFFAOYSA-N (TFAA) [407-25-0] C4F6O3 (MW 210.03) InChI = 1S/C4F6O3/c5-3(6,7)1(11)13-2(12)4(8,9)10 InChIKey = QAEDZJGFFMLHHQ-UHFFFAOYSA-N (oxidant for the conversion of primary and secondary alcohols to aldehydes and ketones, respectively; avoids overoxidation to carboxylic acids; suitable for large-scale oxidation; gives good yields with only small amounts of byproduct methylthiomethyl ethers but alcohols can be converted to trifluoroacetate esters, particularly at higher temperatures; also used for the conversion of primary amines to sulfilimines) Alternate Name: Swern reagent. Physical Data: DMSO: mp 18.4 °C; bp 189 °C d 1.101 g cm−3. TFAA: mp −65 °C; bp 39.5–40 °C; d 1.487 g cm−3. Solubility: DMSO: sol H2O, alcohol, acetone, THF, CH2Cl2. TFAA: sol CH2Cl2, ether, THF. Drying: DMSO: distillation from CaH2 at 56–57 °C/5 mmHg2a or 83–85 °C/17 mmHg;2b storage over 3A molecular sieves. TFAA: distillation. Form Supplied in: colorless liquids; widely available, including ‘anhydrous’ grades of DMSO packed under N2, and 99%+ TFAA. Preparative Method: The active reagent Me2S+O2CCF3 is formed rapidly on the addition of TFAA to DMSO in CH2Cl2 at −78 °C, and is used in situ. Handling, Storage, and Precautions: Dimethyl Sulfoxide is readily absorbed through the skin and should always be handled with gloves in a fume hood; reactions with DMSO form foul-smelling byproducts and should be carried out with good ventilation, and the waste byproducts and liquids used for washing should be treated with KMnO4 solution to oxidize volatile sulfur compounds; DMSO undergoes appreciable disproportionation to dimethyl sulfide (stench) and dimethyl sulfone above 90 °C on distillation at atmospheric pressure;2c Trifluoroacetic Anhydride is toxic, corrosive, and water-sensitive, and reacts violently with DMSO at rt.