Organocatalytic Cascade Reaction of Aliphatic Enals and Benzoylnitromethane: Synthesis of Enantioenriched Tetrasubstituted Cyclohexene Carbaldehyde

Table 1

Influence of solvent, stoichiometric ratio, catalyst, and cocatalyst in the 1a to 2a Michael addition.

Entry		Catalyst	Solvent	Cocatalyst	Ratio	Time (h)	Yield (%)^a	Ee%^b
1		B	DCM	—	1 : 1	4	8	Nd
2		B	DCM	—	1 : 2	3	12	Nd
3		B	CHCl3	—	1 : 1	4	10	Nd
4		B	CHCl3	—	1 : 2	3	11	Nd
5		B	Hexane	—	1 : 1	10	No rxn	—
6		B	Toluene	—	1 : 1	10	No rxn	—
7		B	Et2O	—	1 : 1	10	No rxn	—
8		B	EtOH	—	1 : 1	4	Complex mixture	—
9		B	DMSO	—	1 : 1	4	Complex mixture	—
10		A	DCM	Bac	1 : 1	7	25	93
11		A	DCM	Bac	1 : 2	6	30	93
12		A	DCM	Bac	1 : 3	6	40	96
13		A	CHCl3	Bac	1 : 1	6	20	90
14		A	CHCl3	Bac	1 : 3	6	30	92
15		A	DCM	—	1 : 3	19	35	80

^aYield refers to the isolated compound. ^bThe percentages were determined by chiral HPLC. All entries were carried out at room temperature