Table 1.

Scope of the Allene Initiated Cascade Cyclization

substrate		product(s)	yielda	selectivity
				(trans cis)b
1	X = (PhO2S)2C	2a,b	65%	2.2:1
3	X = O	4a,b	60%	1:8
5	X = (MeO2C)2C	6a,b	65%c	1:8
7	X = (PhO2S)2C	8a,b	35%	7:1
9	X = NTs	10a,b	59%d	4:1
11	X = (MeO2C)2C
			40%	--e
			45%	2.5:1

General conditions: 5 mol % (PhO)₃PAuCl / 5 mol % AgOTf, CH₂Cl₂, rt, 15–45 min.

^aIsolated yields after silica gel chromatography.

^bRelative stereochemistry of ethereal α and α’ stereocenters in the vinyl-bearing oxacycle.

^c~10% of 6c also generated.

^d<10% of the 9-endo product also formed.

^eOnly one isomer detected by ¹H, ¹³C NMR.