Table 1.

Screening of reaction conditions. ^a

Entry	Variation from ‘standard conditions’	Yield of 4a (%)b
1	none	75
2	w/o I2	trace
3	DMF instead of DMSO	trace
4	w/o DTBP	47
5	K2S2O8 (2.0 equiv.) instead of DTBP	19
6	PhI(OAc)2 (2.0 equiv.) instead of DTBP	12
7	70% TBHP (2.0 equiv.) instead of DTBP	43
8	AIBN (2.0) instead of DTBP	70
9	I2 (1.0 equiv.), DTBP (1.0/ 3.0 equiv.)	72/70
10	I2 (0.5/ 2.0 equiv.), DTBP (1.0 equiv.)	60/57
11	At 80/ 120 oC	59/62

^aReaction conditions: 1a (1.2 mmol), 2a (1.0 mmol), 3a (1.0 mmol), I₂ (1.0 mmol) and DTBP (2.0 mmol) in a solution of DMSO (5.0 mL, c = 0.2 M) at 100 ^oC for 4 h under air. ^bIsolated yields.