Catalyzed intramolecular lactonizations using a BAM bifunctional catalyst: optimization of reagents and conditions^a.

Entry	Deviation	Iodine source	Oxidantb	eec (%)	Yieldd (%)	t (d)
1	Tol. only, −20 °C	KI	PIDA	70	14	3
2	−20 °C	KI	PIDA	70	67	3
3	—	I2	AgOAc	12	2	4
4	—	NIS	—	—	0	2
5	—	I2	PIDA	80	40	4
6	—	I2	PhI(O2CCCl3)	0	13	2
7	−20 °C	KI	Togni reagent (Z1)	—	0	4
8	−20 °C	I2	Z1	—	5	2
9	—	I2	Koser's reagent (Z2)	0	11	5
10	—	I2	Dess–Martin reagent (Z3)	37	11	2
11	—	I2	Z4	80	24	4
12	—	I2	NIS	—	8	2
13e	wu: SiO2 quench	I2	PIDA	78	85	3
14e	wu: aq. Na2S2O3	I2	PIDA	85	74	3
15e	StilbPBAM	I2	PIDA	80	33	2
16e	StilbPBAM, NEt3 (100 mol%)	I2	PIDA	—	12	2
17e	6MeOStilbPBAM·HNTf2	I2	PIDA	87	81	2
18e	6MeOStilbPBAM·HNTf2, (0.1 M)	I2	PIDA	87	66	2
19e	6MeOStilbPBAM·HNTf2, (0.075 M)	I2	PIDA	91	70	2
20e	6MeOStilbPBAM·HNTf2, (0.075 M), −40 °C	I2	PIDA	83	80	2

^aGeneral experimental details: the oxidant (100 mol%), KI (100 mol%), catalyst, and carboxylic acid were combined in solvent and stirred for the designated time, prior to workup and analysis; see ESI for complete details. Note that the uncatalyzed reaction, using PIDA/I₂, −20 °C, 3 d, leads to 8 in 29% yield.

^bSolubility observations under these reaction conditions: NIS, PIDA/KI minimally soluble; I₂, PIFA/KI very soluble; PhIO/KI = unknown, but very high reactivity.

^cMeasured by HPLC using a chiral stationary phase.

^dMeasured by ¹H NMR using an internal standard added to the crude reaction mixture after workup.

^eCatalyst loading increased to 10 mol%.