Table 2.

Ligand Optimization for Phosphoramidite Au^I-catalyzed [2+2]-Cycloaddition of 1 with (R,R,R)-9a.^a

entry	2	X	R	yield (%)b	ee (%)c
1	a	C(CO2Me)2	Ph	75	14
2	b	N-Ts	Ph	86	94
3	c	C(SO2Ph)2	Ph	82	85
4	d	N-Boc	Ph	52	81
5	e	N-Ts	2-OMe-C6H4	82	80
6	f	N-Ts	3-OMe-C6H4	80	91
7	g	N-Ts	4-OMe-C6H4	72	80
8	h	N-Ts	4-Cl-C6H4	87	97
9d	b	N-Ts	Ph	67	90

^aReaction conditions: Cat (5 mol%), AgBF₄ (5 mol%), dichloromethane, 25°C, 24h. Only one diastereoisomer was observed in all cases. Trans-2 was used in all cases except for those noted.

^bIsolated yields after silica gel flash column chromatography.

^cEnantiomeric excess determined by enantiodiscriminating HPLC (see Supporting Information).

^dFrom cis-1b.