Science of Synthesis

Couty, F., Science of Synthesis Knowledge Updates, (2017) 2, 464.

This efficient route to azetidines is also discussed in Section 40.1.6.1.2.1. The reduction is best conducted using alane, generated from a mixture of lithium aluminum hydride and aluminum trichloride. This procedure, often referred to as “Ojima’s procedure”, gives high yields of the reduced azetidine because it minimizes over-reduction leading to ring cleavage. Additional recent examples of this reduction illustrating the compatibility of some functional groups present on the azetidine ring are depicted in ‌Table 9‌.[‌49‌–‌55‌] Particularly interesting is the recently described reduction allowing the presence of alkynes or alkenes at the 2-position of the azetidine (entries 5–7).[‌51‌] Lithium aluminum hydride can be employed alone in some cases (entries 9 and 10).[‌53‌,‌54‌] 1-Arylazetidin-2-ones are reduced with sodium borohydride in propan-2-ol without ring opening (entries 11–13). This last procedure produces 2,3-trans-isomers from 2,3-cis-3-azidoazetidinones, suggesting a more complicated mechanism than expected (entries 12 and 13).[‌55‌] On the other hand, such N-aryl substrates can undergo side reactions following Ojima’s procedure, leading to partial ring expansion.[‌52‌]

‌Meeee 8‌ Meeeeeeee ee Meeeeeee-8-eeee ee Meeeeeeeee[‌88‌–‌88‌]

Meeee	Meeeeeee Meeeeeee	Meeeeeeeee	Meeeeee	Meeee (%)	Mee
8		MeM8Me (8 eeeee), eeeeee, 8 e, Me8M		88	[‌88‌]
8		MeM8Me (8 eeeee), eeeeee, 8 e, Me8M		88	[‌88‌]
8		MeMeM8 (88 eeeee), MeMe8 (88 eeeee), eeeeee, 8 e, MMM		88e	[‌88‌]
8		MeMeM8 (8 eeeee), MeMe8 (8 eeeee), ee, 88 eee, Me8M		88	[‌88‌]
8		MeMeM8 (8 eeeee), MeMe8 (8 eeeee), ee, 88 eee, Me8M		88	[‌88‌]
8		MeMeM8 (8 eeeee), MeMe8 (8 eeeee), ee, 88 eee, Me8M		88	[‌88‌]
8		MeMeM8 (8 eeeee), MeMe8 (8 eeeee), ee, 88 eee, Me8M		88	[‌88‌]
8		MeMeM8 (8 eeeee), MeMe8 (8 eeeee), eeeeee, 8 e, Me8M		88	[‌88‌]
8		8. MeMeM8, MMM, 8 °M ee ee, 88 e 8. Mee8M, MM8Me8, ee, 88 e		88	[‌88‌]
88		8. Me8M•8MM, MMM 8. MeMeM8, MMM		–e	[‌88‌]
88		MeMM8, eMeMM, ee, 88 e		88	[‌88‌]
88		MeMM8, eMeMM, ee, 88 e		88	[‌88‌]
88		MeMM8, eMeMM, ee, 88 e		88	[‌88‌]

e Meeeeee eeeeeeeee ee eeeeeeeeeee eeeeeeee eeeeeeee eee eeee eee eeeeeee ee e eeeeee eeeeeeeeee.

e Meeee eee eeeeeeee.

Me eeeeeeee eeeeeee ee eeeeeeeee eeeeeeeeee ee e β-eeeeee eeee e 8,8-eeeeeeeeeeeeeeeee ee eeeee ee ‌Meeeee 8‌.[‌88‌] Meee eeeeeeeee eeeeeeee eeeeeeeee ee eee β-eeeeee eeee eeeeeeeeeeeeeeeeeeeeeeee eeeeeeeee eee 8,8-ee-eeee-eeeee-8-eeeeeeeeeeeeee, eeeeeeee ee eeeeeeee eeee eeeeeeeeeeeeeee eeeeeee, eee eeeee eee eeeeeeeeeeeee eeeeeeeee ee 88% eeeee (88% eeeee ee eeeeeeeee eeeeeeee eeeeeeee).

‌Meeeee 8‌ Meeeeeeee Meeeeeeeee ee e β-Meeeee[‌88‌]

Meeeeeeeeeee Meeeeeeee

eeeee-(8M*,8M*)-8-[(M)-Meee-8,8-eeeeee]-8,8-eeeeeeeeeeeeeeeee (‌Meeee 8‌, Meeee 88); Meeeeee Meeeeeeee:[‌88‌]

Me e eeeeeee eeee ee eeeee-(8M*,8M*)-8-[(M)-eeee-8,8-eeeeee]-8,8-eeeeeeeeeeeeeeee-8-eee (8 eeee) ee eMeMM (88 eM) eee eeeee MeMM8 (8 eeee) ee ee, eee eee eeee eee eeeeeee eee 88 e. Mee eeeeeeee ee eee eeeeeeee eee eeeeeeeee ee MMM eee, ee eeeeeeeeee, eee eeeeeee eee eeeeeee eeee eeeee eee eeeeeeeee eeee MMMe8 (8 × 88 eM). Mee eeeeeeee eeeeeee eeeeee eeee eeeee (Me8MM8), eeeeeeee, eee eeeeeeeeeeee eeeee eeeeeee eeeeeeee. Mee eeeee eeeeeee eee eeeeeeee ee eeeeee eeeeeeeeeeeeee (eeeeee eee, MeMMe/eeeeee 8:8) ee eeeeee eee eeeeeee ee e eeeeee eeeeee; eeeee: 88%.

References