Table 1.
Screening of Reaction Conditionsa
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entry | CpR2Mb | catalyst | % yield 2c | % yield 3d |
1 | Cp2Ti | TiI4(THF)2e | >95 | 0 |
2 | Cp2Ti | TiI4(THF)2 | 0 | >95 |
3 | Cp*2Ti | TiI4(THF)2 | 0 | 0 |
4 | Cp*2Zr | TiI4(THF)2 | 71 | 0 |
5 | Cp*2Zr | TiI4(THF)2f | 55 | 0 |
6 | Cp*2Zr | TiBr4(THF)2 | trace | 0 |
7 | Cp*2Zr | TiCl4(THF)2 | trace | 0 |
8 | Cp*2Zr | TiI4(THF)2g | 0 | 0 |
9 | Cp*2Zr | none | 0 | 0 |
Reaction conditions: metallocene (0.05 mmol), diphenylacetylene (0.05 mmol), catalyst (0.05–0.0005 mmol of Ti), Zn0 (0.05–0.0005 mmol), 0.5 mL of C6H5Br, 115 °C, 3 h.
Cp = cyclopentadiene; Cp* = pentamethylcyclopentadiene.
Determined by quantitative GC-FID with respect to an internal standard (1,3,5-trimethoxybenzene).
Determined by 1H NMR with respect to an internal standard (1,3,5-trimethoxybenzene).
Reaction conducted with 100 mol % TiI4(THF)2.
Reaction conducted with 0.1 mmol of diphenylacetylene.
Reaction conducted in the absence of Zn0.