Table 2.

Chroman formation^a

entry	catalyst 6	product 4v yield [%]	product 4v er	product 5a yield [%]	product 5a er
1	6c	22	70:30	28	60:40
2	6d	46	66:33	33	60:40
3	6f	22	80:20	55	79:21
4	6g	31	82:18	59	87:13
5b	6h	37	21:79	16	49:51
6	6i	39	89:11	50	81:19
7c	6g	5	-	69	84:16
8d	6g	-	-	72	85:15
9d,e	6g	-	-	40	99:1

^aReactions were run at 80 °C with 0.4 mmol phenol, 0.8 mmol aldehyde, and 0.8 mmol boronate for 24 h in toluene (0.3 M) unless otherwise indicated. Diastereomeric ratios were 2:1 as determined by ¹H NMR unless otherwise indicated. Enantiomeric ratios are reported for the major diastereomer.

^b(S)-enantiomer of catalyst used. Mesityl = 2,4,6-trimethylbenzene.

^cReaction was run in sealed tube at 120 °C for 24 h.

^dReaction was run in a sealed tube at 80 °C for 24 h and then 150 °C for 1 h.

^eProduct was recrystallized from hot hexanes. The diastereomeric ratio was >20:1 as determined by ¹H NMR.