Ionic-Liquid-Mediated MacMillan’s Catalyst for Diels-Alder Reaction

Table 1

Screening of different ionic liquids for MacMillan’s imidazolidinone catalyst 1 catalysed Diels-Alder reaction between cyclohexene 1 and acrolein 2.

Entry	Ionic liquid	Ionic liquid amount (in mmol)	Yield^a (%)	endo : 𝑒𝑥𝑜^b	ee (%)^c
(1)	[bmim][Cl]	0.05	64	1.5 : 1	65
		0.10	63	1.6 : 1	67
(2)	[bmim][PF6]	0.05	68	1.8 : 1	71
		0.10	70	2.2 : 1	74
		0.01	65	3 : 1	71
		0.02	68	3.5 : 1	78
(3)	[bmim][NTf2]	0.05	84	4.2 : 1	88
		0.10	91	5.6 : 1	92
		0.5	94	19 : 1	95
		1	92	96 : 1	91
(4)	MeOH/H2O	0.95 mL : 0.05 mL	8	2.3 : 1	87
(5)	CH3CN/H2O	0.95 mL : 0.05 mL	84	2.3 : 1	90

^aIsolated yield, ^bendo : exo ratio was determined by ¹H NMR, ^cee% was determined by HPLC, ^d1 mL MeOH/H₂O system.