Optimisation of reaction conditions for the oxidation of thioanisole^a.

Entry	Catalyst loading [mol%]	Solvent	Conversionb [%]
1	10c	Acetonitrile	4
2	10	Acetonitrile	89
3	10	γ-Valerolactone (GVL)	28
4	10	N-butyl-2-pyrrolidone (NBP)	6
5	10	Cyclopentylmethyl ether (CPME)	4
6	10	2-MeTHF	9
7d	10	scCO2	45
8	10	Neat	99 (99) e
9	1	Neat	87
10	0.1	Neat	79
11	—	Neat	81

^aReaction conditions: 5a (0.24 mmol), H₂O₂ (2.5 equiv.), l-proline, solvent (3.8 M) for 2 hours at 40 °C.

^bConversion was determined by LC-MS analysis of the reaction mixture; entries were performed in duplicate.

^cReaction conditions: acetonitrile (0.33 M).

^dReaction conditions: stirred for 2 hours under 80 bars of CO₂ at 40 °C.

^eIsolated yield.