Enantioselective Lactonization of 3,3,6-Trimethyl-4(E)-heptenoic Acid Esters

Table 1

Isolated yield.

Substrate	T (°C)	t (h)	X	Composition of product mixture							Yield (%)
				δ-Lactones (% GC) (%ee)				γ-Lactones (% GC) er.
2a	20	12	Br	3	59	28	(5S,6R)	4	41	57 : 43	89
2a	0	24	Br	3	59	34	(5S,6R)	4	41	52 : 48	76
2a	−20	36	Br	3	56	35	(5S,6R)	4	44	50 : 50	76
2a	−40	72	Br	3	54	36	(5S,6R)	4	46	50 : 50	68
2b	−20	36	Br	3	57	37	(5R,6S)	4	43	52 : 48	76
2c	0	24	Br	3	58	10	(5R,6S)	4	42	50 : 50	73
2c	−20	36	Br	3	57	24	(5R,6S)	4	43	44 : 56	69
2d	0	24	Br	3	60	0		4	40	50 : 50	81
2d	−20	36	Br	3	77	11	(5R,6S)	4	23	40 : 60	73
2e	0	24	Br	3	57	0		4	43	45 : 55	81
2e	−20	36	Br	3	55	0		4	45	44 : 56	78
2f	0	24	Br	3	62	5	(5R,6S)	4	38	49 : 51	77
2f	−20	36	Br	3	66	13	(5R,6S)	4	34	49 : 51	80
2a	0	36	I	5	83	15	(5S,6R)	6	17	59 : 41	72
2a	−20	60	I	5	80	28	(5S,6R)	6	20	58 : 42	71
2a	−40	100	I	5	75	30	(5S,6R)	6	25	55 : 45	62
2c	0	36	I	5	85	13	(5R,6S)	6	15	45 : 55	77
2c	−20	60	I	5	83	17	(5R,6S)	6	17	48 : 52	68
2d	0	36	I	5	84	9	(5R,6S)	6	16	44 : 56	73
2d	−20	60	I	5	72	12	(5R,6S)	6	28	46 : 54	69
2a	20	72	Cl	7	43	8	(5S,6R)	8	57	50 : 50	76
2c	20	72	Cl	7	50	3	(5R,6S)	8	50	50 : 50	81