Table 1.

Cyclization of Methyl diazo(2-phenylmethyleneaminophenyl)acetate Catalyzed by Lewis Acids

entry	Lewis acid 1 mol%	reaction time (min)	yield (%)
1	ZnCl2	60	very low conversion
2	BF3•Et2O	10	100
3	TiCl4	5	100
4	SnCl4	10	100
5	Mg(OTf)2	60	no conversion
6	Sn(OTf)2	15	100
7	In(OTf)3	5	100
8a	Zn(OTf)2	40	100
9	Ni(OTf)2	15	100
10	Cu(OTf)2	5	100
11	Sc(OTf)3	5	100
12	La(OTf)3	60	very low conversion
13	Yb(OTf)3	20	100

^aReaction was complete in less than 10 min when 5 mol% Zn(OTf)₂ was used; reaction was complete in 10 h when 0.1 mol% Zn(OTf)₂ was used.