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. Author manuscript; available in PMC: 2020 May 6.
Published in final edited form as: J Am Chem Soc. 2020 Feb 20;142(9):4390–4399. doi: 10.1021/jacs.9b13173

Table 2.

Substrate Scope of One-Pot In Situ Pyrazole Synthesis from Alkynes and Nitrilesa

graphic file with name nihms-1582304-t0012.jpg
entry R1 R2 R3 product yield (%)
1b 4-Me-C6H4 Et Et 1 75c
2b Ph Et Et 1b 79c
3 Ph Et Et 1b 56
4 4-MeO-C6H4 Et Et 1c 52
5 4-CF3-C6H4 Et Et 1d 49
6 iPr Et Et 1e 54
7 Me Et Et 1f 43
8 Me Ph Me 1g 28
9 Ph Ph Me 1h 54
10 Ph Me Me 1i 52
11 Ph 4-t-BuC6H4 4-t-BuC6H4 1j 37
a

Conditions: 0.025 mmol of [py2TiCl2(NPh)]2, 0.05 mmol (2 equiv) of alkyne, 0.05 mmol (2 equiv) of nitrile, 0.5 mL of PhBr, 115 °C, 4h; yields with respect to alkyne are determined in situ via 1H NMR against internal 1,3,5-trimethoxybenzene standard.

b

Conditions: 0.025 mmol of [py2TiCl2(NPh)]2, 0.15 mmol (6 equiv) of alkyne, 0.15 mmol (6 equiv) of nitrile, 0.5 mL of PhBr, 115 °C, 1 h.

c

Yields reported with respect to [py2TiCl2(NPh)]2, which is the limiting reagent under condition B.