Table 1.

Reaction Parameters for Annulation to Pyrazolopyrimidine 8^a

entry	Variation	Yield %b
1	None	75
2	[Cp*RhCl2]2 (5%)	61
3	no Rh	0
4	NaOAc instead of KOAc	60
5	no KOAc	39
6	no PivOH	27
7	160 °C	73
8	chlorobenzene as solvent	57
9	ylide 7a (1.1 equiv)	67
10	[Cp*IrCl2]2 (5%) and AgSbF6 (20%)	28
11	[Cp*Co(MeCN)3](SbF6)2 (10%)	21
12	0.1 M	62
13	0.4 M	85 (82)c
14	0.4 M, no sieves	75
15	0.4 M, [Cp*Rh(MeCN)3](SbF6)2 (5%)	77
16	0.4 M, [Cp*Rh(MeCN)3](SbF6)2 (2.5%)	38
17	0.4 M, conventional heating, 100 °C, 16 h	82

^aConditions: 5a (0.20 mmol), 6a (0.10 mmol), 7a (0.15 mmol)

^bYield determined by ¹H-NMR relative to 1,3,5-trimethoxybenzene as external standard.

^cIsolated yield of a 0.30 mmol scale (see Scheme 2).