Table 3.

Synthesis of chromenes by the 1,4-addition of boronic acids to β-(2-hydroxyaryl)enones [34].

entry	R1	R2	R3	Ar	additive (equiv)	yield A + B (%) ratio A/B	yield C (%)	ee C (%)
1	H	Me	Me	Ph	–	99 (1:13)	90	96
2	H	Me	Me	4-MeO-C6H4	AgBF4 (0.1)	96 (1:13)	90	97
3	H	Me	Me	3-MeO-C6H4	AgBF4 (0.1)	96 (1:13)	94	97
4	H	Me	Me	3,4-(CH2O2)-C6H3	AgBF4 (0.1)	99 (1:16)	89	98
5	H	Me	Me	4-Me-C6H4	–	99 (1:13)	94	97
6	H	Me	Me	4-Ac-C6H4	AgBF4 (0.1)	99 (1:16)	90	96
7	H	H	Ph	Ph	–	99 (2:1)	92	99
8	H	OMe	Me	Ph	–	99 (1:16)	94	95
9	t-Bu	t-Bu	Me	Ph	–	94 (1:99)	90	–