Table 3.

Studies on the reduction of unsaturated ketones using spiroborate ester 1.^a

Entry	Substrate	Cat. (%)	Borane	Yieldb (%)	Eec (%)
1		25	BH3- DMS	87g	79
2		10	BH3- DMS	73	80
3		1	BH3- DMS	73	70
4		10	BH3- DEA	-d	67
5		10	BH3- THFe	-d	72
6		10	BH3- THFf	-d	74
7		25	BH3- DMS	55g	72
8		10	BH3- DMS	83	80
9		1	BH3- DMS	87	62
10		25	BH3- DMS	73g	81
11		10	BH3- DMS	83	83
12		1	BH3- DMS	88	65

^aThe reaction was carried out using 0.6 equiv of borane reagent in THF at 0 °C.

^bYield after distillation in a Kugelrohr apparatus.

^cDetermined by GC of the acetate on a chiral column.

^dThe product was not isolated.

^eBorane-THF complex was stabilized by < 0.005M of NaBH₄.

^fBorane-THF complex was stabilized by < 0.005M of N-tert-butyl-N-isopropyl- methylamine.

^gYield after column chromatography.