Substrate Directed Regioselective Monobromination of Aralkyl Ketones Using N-Bromosuccinimide Catalysed by Active Aluminium Oxide: α-Bromination versus Ring Bromination

Table 3

α-Bromination of acetophenone derivative(s) containing moderate activating/deactivating or high deactivating groups^a.

Entry	Substrate (1)		Product (2)	Time/min	Yield^b/%	Selectivity/%; 2 : 3 : 𝟏^c	Lit. Ref.
	R′	R
1	H; 1a	H	2a	10	89	89 : 09 : 02	[26]
2	H	Me; 1b	2b	10	74	74 : 22 : 04	[26]
3	2′-Me; 1c	H	2c	12	86	86 : 08 : 06	[26]
4	3′-Me; 1d	H	2d	11	88	88 : 05 : 07	[26]
5	4′-Me; 1e	H	2e	10	90	90 : 06 : 04	[26]
6	4′-Et; 1f	H	2f	12	85	85 : 09 : 06	[26]
7	4′-CN; 1g	H	2g	9	73	73 : 11 : 16	[39]
8	3′-Cl; 1h	H	2h	7	76	76 : 10 : 14	[26]
9	4′-Cl; 1i	H	2i	9	92	92 : 05 : 03	[26]
10	4′-Br; 1j	H	2j	9	87	87 : 08 : 05	[26]
11	4′-MeO; 1k	H	2k	6	72	72 : 19 : 09	[26]
^d12	3′-NO2; 1l	H	2l	11	41	41 : 19 : 40	[26]
^d13	4′-NO2; 1m	H	2m	14	49	49 : 16 : 35	[26]

aReaction conditions: 1 (10 mmol), N-bromosuccinimide (12 mmol), and 10% (w/w) acidic Al₂O₃ in methanol (20 mL) at reflux temperature.
bIsolated yield.
cUnreacted substrate.
d5% acidic Al₂O₃ was applied.