Table 1.

Catalytic Enantioselective Synthesis of 2-Vinylchromanes 1a–c.

entrya	substrate	R	catalyst (mol %)	temp (°C)	yield (%)b12	yield (%)b1	ee (%)c1
1	(E)-11a	H	7 (2)	38	—	86	89 (R)d
2	(E)-11a	H	10 (2)	38	—	72	80 (S)
3	(E)-11a	H	ent-9 (2)	38	43	41	80 (S)
4	(E)-11a	H	8 (2)	38	13	81	87 (R)
5	(E)-11a	H	7 (0.5)	23	—	91e	94 (R)e
6	(E)-11a	H	ent-7 (0.5)	23	—	97e	92 (S)e
7	(E)-11b	4-Br	7 (0.5)	23	—	96e	80e
8f	(E)-11b	4-Br	7 (0.5)	23	—	94e	90e
9g	(E)-11c	4-OMe	7 (0.5)	23	—	92e	91 (R)d,e
10	(Z)-11a	H	ent-7 (0.5)	23	—	92e	9 (R)e

^a[11] = 0.2 M; reaction time 8–18 h.

^bIsolated yield after purification on silica gel.

^cDetermined by HPLC analysis using a enantioselective stationary phase.

^dAbsolute configuration determined by comparison of optical rotation data with that reported in the literature.^4b

^eMean values of duplicate reactions.

^fThe solvent was CHCl₃.

^gReaction time was 30 h.