Table 3.

Selective carbocyclization of allenynes 1 yielding borylated vinylallenes 5^[a]

Entry	Allenyne	Product	5/4[b]	Yield of 5 [%][c]
1			>20:1	77
2			>20:1	73
3			>20:1	56
4			>20:1	79 87[d]
5			20:1	77
6			>20:1	70
7[e]			>20:1	37

^[a]Unless otherwise noted, 1 (0.1–0.2 mmol), B₂pin₂ (1.3 equiv), Pd(OAc)₂ (2 mol %), BQ (1.1 equiv), and BF₃⋅Et₂O (20 mol %) were dissolved in THF (5 mL mmol⁻¹) and stirred at 50 °C for 20 h.

^[b]Ratio determined by ¹H NMR analysis of the crude reaction mixture.

^[c]Yield of the isolated product.

^[d]1 mmol of 1 d was used.

^[e]2 mol % of [Pd(CH₃CN)₄][(BF₄)₂] was used in place of Pd(OAc)₂ and BF₃⋅Et₂O. E=CO₂Me.