Table 2.

Screening of solvents in catalyzed coumarin synthesis.^a

Entry	Solvent	Time (h)	Yield (%)b
1	toluene	28	26
2	isopropanol	28	19
4	EtCN	28	8
5	dioxane	28	2
5	hexane	20	7
6	CHCl3	28	21
7	MeOH	22	77
8	MeOH	22	47c
9	glycol	22	3
10	glycerol	16	27
11	MeOH/H2O (1:1)	16	30
12	CF3CH2OH	16	43
13	MeCN	16	6
14	DMSO	16	–
15	tert-butanol	23	36

^aReactions were performed on a 0.5 mmol scale in 1 mL of solvent. ^bScreening yields were determined by GC and/or HPLC analysis with N-pivaloylaniline as the internal standard. ^cPCy₃ was used as the catalyst instead of n-Bu₃P.