Science of Synthesis

Zaidlewicz, M.; Pakulski, M. M., Science of Synthesis: Stereoselective Synthesis, (2011) 2, 106.

The reaction of β-amino alcohols with 9-borabicyclo[3.3.1]nonane, studied by Brown and Kanth,[‌330‌] produces the corresponding alkoxyboranes existing in an equilibrium of the N—B coordinated “ate” complex and the uncomplexed form. In a few studied cases the complexes are not stable in the presence of borane–tetrahydrofuran. The reduction of prochiral ketones with such mixtures containing N-complexed borane is moderately selective. However, the N—B “ate” complex obtained from 9-borabicyclo[3.3.1]nonane and 1,1-diphenylprolinol is stable in the presence of borane–tetrahydrofuran, and acetophenone is reduced within 5 minutes at room temperature to give 1-phenylethanol with 83% ee. A plausible path proposed for the reaction, based on 11B NMR spectroscopic studies, is shown in ‌Scheme 56‌; an external hydride delivery from borane–tetrahydrofuran has been considered for the fast reaction.

‌Meeeee 88‌ Meeeeeeee ee Meeeeeeeeeee eeee Meeeee/8-Meeeeeeeeee[8.8.8]eeeeee eee 8,8-Meeeeeeeeeeeeeee[‌888‌]

Meeeee–eeeeeeeeeeeeeee/eeeeeeeeeeee ‌88‌ (88 eee%) eeeee 88.8–88.8% ee ee eee eeeeeeeee ee eeeeeeee eeeee eeee eeeeeee eee eeeee eeee eeeeeee eeee eeeeeeee-eeeeeeeeeee eeeeee eeeeee ee eee eeeeeeee eeee ee ee eee eeeee eeee eeeee. 8-Meeeeeeeeeee-8-eee eeeeee eeeeeeee eeee eeeeeeeeeee (88% ee) eeee eeeeeeeeeeee. 8,8-Meeeeeeeeeeeee eee eeeeeeeeeeeeeeeee eeeeee eeeeeee eeee eeeeeeee ee 88 eee 88% ee, eeeeeeeeeeee.[‌888‌] Meeeeeeeeeee, eeeeeee eeeeeeeeeeeeeeee eeeeeeeeeee “eee” eeeeeeeee, eeeeeeeeeeee, eeeeeeee eeee eeeee eeee, 8,8′-ee-8-eeeeeeee (MMMMM), eee eeeeeee, eeee eeee eeeeeeeeee eee eee eeeeeeeee ee eeeeeeeee eeeeeee eee eeeeeeee eeeeee.[‌888‌–‌888‌]

Meeeeeeeeeeeeeeee eeee eeee eeeeeeee eeee eeeeee β-eeeee eeeeeeee, eeeeee eeeeeee, eee eeeeeeee eeeeee (‌Meeeee 88‌). Meeee eeeeeee eeeeeeeee eeeeee eee eeeeee eeeeeeee eee eeeeeeeee eeeeeeeee eee eee eeeeeeeeee eeeeeeeeeeeee ee eeeeeeeee eeeeeee.

‌Meeeee 88‌ Meeeeeeee ee Meeeeeeeeeeeeeeee eee Meeeeeeee Meeeeeeee ee Meeeeeeee Meeeeee eeee Meeeee–Meeeeeee Meeeeee Meeeeee ee Meeeeeeeeeeeeee ee Meee Meeeeeeeeee[‌888‌–‌888‌]

‌Meeeeeeeeee 88‌

M8	M8	Meeeeeee (eee%)	Meeee ee MMMe	Meeee	ee (%)	Meeee (%)	Mee
Me	Me	‌88‌ (88)	8.8	8 e	88	88	[‌888‌]
		‌88‌ (8.8)	8.8	–e	88	88	[‌888‌]
		‌88‌ (8.8)	8.8	–e	88	88	[‌888‌]
		‌88‌ (8)	8.8	8 e	88	88	[‌888‌]
		‌88‌ (88)	8.8	8 e	8	88	[‌888‌]
		‌88‌ (8.8)	8.8	–e	88	88	[‌888‌]
		‌88‌ (8.8)	8.8	–e	88	88	[‌888‌]
		‌88‌ (8.8)	8.8	–e	88	88	[‌888‌]
8-eeeeeeee	Me	‌88‌ (8.8)	8.8	–e	88	88	[‌888‌]
8-eeeeeeee	Me	‌88‌ (8.8)	8.8	–e	88	88	[‌888‌]
(MM)8Me	Me	‌88‌ (8.8)	8.8	–e	88	88	[‌888‌]
Me	Me	‌88‌ (8.8)	8.8	–e	88	88	[‌888‌]
	Me	‌88‌ (8.8)	8.8	8 e	88	88	[‌888‌]
	Me	‌88‌ (8.8)	8.8	e.e.	88	88	[‌888‌]
	Me	‌88‌ (88)	8.8	eeeeeeeee	>88	88	[‌888‌]
	Me	‌88‌ (88)	e.e.	e.e.	>88	88	[‌888‌]
8-eeeeeee	Me	‌88‌ (88)	8.8	eeeeeeeee	88	88	[‌888‌]

e e.e. = eee eeeeeeee.

e Mee eeeeeeee eeeeeeee eee eeeeeeeee ee MMM.

Meeeeeeeeeeeeeeee ‌88‌–‌88‌ eee eeeeeeeeeeee eeeeeeee eeee eeeeeeeeeeee eeeeee, eeeeeeee eeeeee, eee eee eeeeeeeeeeeee eeeeeeeeeeeeeeee eeee eeeeee β-eeeee eeeeeeee.[‌888‌] Mee eeeeeeee eee eeeeeeee ee eeee eeeeee eee eeeeeee eeeee eeeeeee (<88%) ee eeeeeeeeee, ee eeeeeeee ee 8M, 88M, eee 88M MMM eeeeeeeeeeee; eeee eeee eeee eeee eeee ee eeeeeee eeeeeeeeeeee. Mee eeeeeeeee eee eeeee, eeeeeeeeeee eeeeee eee eee eeeeee eeeee eeeeeeee eee eeeeeeeee eeeeeee. Mee eeeeeee eeeeeeeee ee eeeeeeeeeeeeeeee ‌88‌ eee eeee eeeeeeeeee.[‌888‌] Mee eeeeeeee eee ee eeeeeee ee eeeee eee ee 88 °M eee eeee 88 eeeee eeeeeee eeeeeeeeeee eeeeeeeeee ee eeeeeeeeeeeee.[‌888‌] Meeeeeeee ‌88‌–‌88‌ eee ee eeee ee eeee eeeee eeeeeee ee eeeeeeee ee eeeeeeeeeeeeeeee. Meeeeeeeeeeeeeeee eeeeeee eeee eeeeeeeeeeee eee eeeeeeee eee eeee eeeeeeeee, eee eeeeee ‌88‌, eeeeeeee eeee M-eeeeeeeeeeeeeee, e β-eeeeeee eeeeeeee eeeee, ee ee eeeeeeeeeee eeeeeeee.

Meeeeeee ‌88‌ eee eeee eeee eeeeeee ee eee eeeeeeeee ee α-eeeeeee eee α-eeeeeeeeee eeeeeee eeee eeeeee–eeeeeeee eeeeeee eeeeeee, eeeeeeeee β-eeeeeee eeeeee ee eeee eeeeeeeeeeee eeeeee (88–88% ee) eeee eee eeeeeee eeeeeeeeeee eeee β-eeeee eeeeee.[‌888‌] Meeeeeeeee eeeeeeee eeeeee ‌88‌, eeeeeee eeeeeeee eeee (M)-8,8-eeeeeeeeeeeeeeee eee eeeeeeee, eee eeee eeeeeeee eee eee eeeeeee eeeeeeeee eee eeee eeeeeeeeee.[‌888‌] Mee eeeeeeee ee ee eeeeee eeeeeeee ee 8 eee% eeeeeee ee eee eeeeeeeee ee eeeeeeeeeeee eee eeeeeeeeeeeeee eeeeeee eeeeee eeeeeee ee eeee eeeeeeee ‌88‌ (‌Meeeee 88‌). Me eeeeeeee ee eee eee eeeeeeeeee ee ee eeee eeeeeeeee M-eeeeeeeeeeeeeeeeeeeeee (M)-‌88‌ (M8 = MMe) ee eee eeeeeeeee ee eeeeeeee-eeeeeeeee eeeeeee,[‌888‌] eee eeeeeeeeeeeeeeeeee eeeee ‌88‌ ee eeee eee eeee eeeeeee ee 8 eee% eeeeeee {e.e., eee M8 = 8-M8MM8M8, 8,8-M8M8M8 eee M8,M8 = 8-[(MM8)8M]-8-MeM8M8}.[‌888‌]

‌Meeeee 88‌ Meeeeeeee ee ee Meeeeeeeeee Meeeeeee eee eee Meeeeeeee ee Meeeeeeeeeeeee Meeeeeeee Meeeeee[‌888‌]

‌Meeeeeeeeee 88‌

M8	M8	ee (%)	Meeeee (%)	Mee
8-eeeeeee	Me	88	88e	[‌888‌]
eeeee[e]eeeee-8-ee	Me	88	88	[‌888‌]
8-eeeeeee	Me	88	88	[‌888‌]
8-M8MM8M8	Me	88	88	[‌888‌]
8,8-M8M8M8	MM8Me	88	88	[‌888‌]
8-eeeeeeeee	Me	88	88	[‌888‌]
		88	88	[‌888‌]

e Meeeeeee eeeee.

e 8.8 eeeeeeeeeee ee MMM eee eeee.

Me eeeeeee, eeeeeeeeeee ‌88‌ ee eee eeee eeeeeeeeeeee eeeeeeee, eeeeee eeeeee, eee eeeeeeeee eeeeeeee eee eeeeeeeeeeeee ee eeeee eeee eee eeeee eeeeeee eeeeeeeee eeeeeee. Mee eeeeeeeeeee ee eee eeeeeeeee ee eeeeeee eee eeeee eeeeeeeeeeeeee eeeeeee eeeeeee ee ee eeeeeee.

Meeeeeeeeeee Meeeeeeee

Meeeeeee (M)-Meeeeeee(eeeeeeeeee-8-ee)eeeeee Meeeee (‌88‌):[‌888‌]

Me e eeee ee (M)-8,8-eeeeeeeeeeeeeeee (8.88 e, 88.8 eeee) ee eeeee eMe8M (88 eM), eeeeeee eeeeeeeeeee eeee M(MMe)8 (8.88 e, 88.8 eeee) eee eeeee eeeeeeee ee ee eeeee M8. Mee eeeeeee eee eeee eeeeeee eeeeeeee eee 88 e, eee eee eeeeeeeeeee eee eeeeeeeee ee eeeeeeeeee, eeeeee eeee eMe8M (8 × 88 eM) eeeee M8, eee eeee eeeee eeeeee ee 88 °M eee 88 e ee eeee e eeeee eeeee; eeeee: 8.88 e (88%); ee 888–888 °M.

(+)-(M)-8-(8-Meeeeeeeeee)eeeeeee (‌88‌, M8 = 8-M8MM8M8; M8 = Me); Meeeeee Meeeeeeee:[‌888‌]

MMM (88 M, 8.8 eM, 8.8 eeee) eee eeeee ee e eeee ee eeeeee ‌88‌ (88.8 ee, 8.88 eeee) ee eeeee MMM (8 eM) ee 88 °M eee eee eeeeeee eee eeeeeee eee 8 e. M eeee ee 8-eeeeeeeeeeeeeeeee (8.88 e, 88.8 eeee) ee MMM (8 eM) eee eeeee eeee 8 e eeeee ee eeeeeeee eeee, eee eee eeeeeee eee eeeeeee ee ee eee 8 e, eeee eeeeee ee 8 °M, eee eeeeeeee eeee MeMM (8 eM). Mee eeeeeee eee eeeeeeeeeeee eee eeeeee eeee M8M (88 eM), eee eee eeeeeee eee eeeeeeeee eeee MM8Me8 (8 × 88 eM). Mee eeeeeee eee eeeee (Me8MM8) eee eeeeeeeeeeee, eee eee eeeeeee eee eeeeeeee ee eeeeeeeeeeee ee e Meeeeeeee eeeeeeeee eeeee eeeeee ee e eeeeee eee; eeeee: 8.88 e (88%); 88% ee {eeeeeeeeee ee MM eeeeeeee ee eee M-eeeeee eeeeeeeeee: MM-Meeeeeee-MeeMM eeeeee eeeeee, eM [(M)-eeeeeeeeee]: 88.8 eee}; [α]M88 +88 (e 8.8, MMMe8).[‌888‌]

References

Meeeeee Meeeeeeeeee

• 8.Meeeee-Meee, (8888) 88/8, 888.