Optimisation of reaction conditions for the Michael addition of 4-methoxybenzenethiol to chalcone^a.

Entry	Catalyst loading [mol%]	Solvent	Conversionb [%]	ee [%]
1	1.5	Toluene	91	40
2	1.5	CPME	87 (85) d	40
3	1.5	NBP	86	0
4	1.5	GVL	80	0
5	1.5	2-MeTHF	99	0
6c	1.5	Liquid CO2	67	18
7	1.5	Neat	88	14
8	0.1	Neat	86	—
9	0.005	Neat	88	—
10	0	Neat	58	—
11	0	Toluene	6	—

^aReaction conditions: 2a (0.24 mmol), methoxybenzenethiol (1.1 equiv.), cinchonine, solvent (0.33 M), 4 hours at −20 °C.

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

^cReaction conditions: stirred for 4 hours under 100 bars of CO₂ at −20 °C.

^dIsolated yield.