An Efficient Synthesis of Phenols via Oxidative Hydroxylation of Arylboronic Acids Using (NH₄)₂S₂O₈

Table 2

Effects of (NH₄)₂S₂O₈ on the hydroxylation of 1a ^a.

Entry	(NH4)2S2O8 (equiv.)	Time (h)	2a yield^b,c (%)
1	0.0	3	Nr
		10	Nr
		24	Nr
2	1.0	3	39^b,c
		10	52^b,c
		24	65^b,c
3	2.0	3	64^b,c
		10	79^b,c
		24	85^b,c
4	2.5	3	98^d

aReaction conditions: 1a (0.41 mmol), MeOH : H₂O 6 : 1 (3 mL), and 80°C. ^bThe reaction did not reach completion. ^cYield determined by ¹H NMR of the crude reaction product. ^dYields obtained after chromatographic purification. Nr: no reaction.