Table 1. Optimization of triethylborane-promoted tricyclopentane ring-opening.

Entry	Substrate	x (equiv.)	y (mol%)	T	t	Yield a (%)
1	7a	1.3	10	rt	15 min	83
2	7a	1.3	10	0 °C	15 min	87
3	7a	1.3	5	0 °C	15 min	89
4	7a	1.3	1	0 °C	15 min	95
5	7a	1.3	0.5	0 °C	15 min	(67 : 33)
6	7a	1.1	1	0 °C	15 min	92
7	7a	2.0	10	rt	16 h	98 b
8	7a	2.0	0	rt	20 h	(60 : 40) c
9	7a	2.0	0	rt	20 h	(33 : 67)
10	8a	1.3	10	rt	20 h	47 d
11	8b	1.3	10	rt	15 min	67
12	8b	1.3	10	0 °C	15 min	73
13	8b	1.3	1	0 °C	15 min	(60 : 40)

^aIsolated yields. Figures in parentheses indicate incomplete reactions, and the ratio of starting material to product as judged by ¹H NMR spectroscopic analysis of the crude reaction mixture.

^bReaction carried out in Bu₂O (0.19 M).

^cReaction carried out in the dark.

^dIsolated as a 6 : 1 mixture of 6a : staffane.