Table 2. Yield and Regioselectivity of Thallium(I) Dihydrobis(pyrazolyl)borate Complexes (2a–f_Tl)^a.

Pyrazole	R3	R4	R5	BpxTl (2Tl) Yield (%)b
1a	tBu	H	H	90
1b	tBu	Br	H	87
1c	tBu	NO2	H	92
1f	Ms	Br	H	76c

^aReaction conditions: 1a–c (10.1 mmol), NaH (10.1 mmol), toluene (50 mL) 30 min at 0 °C, BH₂Cl·SMe₂ (5 mmol) 24 h at rt. Evaporation and addition of THF (30 mL), TlOAc (7.5 mmol), 2 h at rt.

^bIsolated yield.

^c20.1 mmol of 1f and NaH (4.02 equiv) were used.