Science of Synthesis

Hodgson, D. M.; Humphreys, P. G., Science of Synthesis, (2008) 36, 645.

Lewis acids are a mild alternative to lithium amides for the rearrangement of epoxides to allylic alcohols[‌337‌] and, due to the decreased basicity of the Lewis acids, more functional groups can be tolerated, including potentially enolizable esters and ketones.[‌338‌,‌339‌] The Lewis acid trimethylsilyl trifluoromethanesulfonate in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene or lutidine is a reagent combination that causes the rearrangement of epoxides to allylic alcohols,[‌338‌] and gives reasonable yields with a variety of cyclic substrates. Here, the least sterically demanding proton is abstracted by the base to give the least substituted E-allylic alcohol; however, mono and acyclic 2,3-dialkyl substituted epoxides fail to react under these conditions.[‌338‌] An alternative silicon-based Lewis acid combination is iodotrimethylsilane and 1,5-diazabicyclo[4.3.0]non-5-ene, although competing deoxygenation reactions, particularly with trisubstituted cyclic epoxides, limit its value.[‌339‌] Boron trifluoride–diethyl ether complex with tetrabutylammonium iodide is another mild reagent combination that is used to convert epoxides into allylic alcohols by epoxide ring opening, followed by abstraction of the most accessible β-proton.[‌340‌] An example of this is the synthesis of diol ‌147‌ (‌Scheme 70‌).

‌Meeeee 88‌ Meeee Meee Meeeeeee Meeeeeeeeeeee ee ee Meeeeee ee ee Meeeeee Meeeeee[‌888‌]

Meeeeeee(MM) eeeeeeeeeeee ee eeeeeee eeeeeeee Meeee eeee eee eee eeeeeeeeeeeee ee e 8,8-eeeeeeeeeeee ee eeeeeee ee eeeeeee eeeeeee. Mee eeeeeee, eeeeeeeee ee 8,8-eeeeeeeeee (‌888‌) eeee 8.8 eeeeeeeeeee ee eeeeeeee(MM) eeeeeeeeeeee ee eeeeeeeeeeeeeee eee 88 eeeee ee eeee eeeeeeeeeee eeeee eee M-eeeeeeeeee eeeeeee eeee ‌888‌ ee 88% eeeee. Mee eeeeeeee ee eeeeee ee eeeeeee eee eee eeeeeeeeeee eeeeee ee eeeee eeeeeee–eeeeeeee eeeeeeee eeeeeee ‌888‌ (‌Meeeee 88‌).[‌888‌]

‌Meeeee 88‌ Meeeeeeeee ee 8,8-Meeeeeeeee eeee ee Meeeeee Meee ee eee Meeeee ee Meeeeeee(MM) Meeeeeeeeeee[‌888‌]

Meeee eeeeee eeee ee eeeeeeeeeeeeeee M-eeeeeeeeee-M-eeeeeeeeeeeeee eee eeee ee eeee eeeeee ee eeee eeeee ee eeeeeeeee eeeeeeee eeee eeeeeee eeeeeeee, eeeeeeee eeee eeeeee eee eeeeeeeee eeeeee eeee eeeeeee ee eee eeeeeee eeeeeeee ee eeeee eeeeeeeeee eeeee eeee eeeeeeee.[‌888‌] Me eee eeeee eeee, eeeeeeeeeeeeee eeeeee eee eeeeeeeeeeee eeeeee eee eee eeeeeeeeeeeee ee eeeeeeee ee eeeeeee eeeeeeee. Meee eeee e eeeeeeeeee eee eeeeeeee, eee eeee Meeee eeeeeee, eeeee eeee eeeeeeeeeeee ee eee eeeeeee eeeeee eeee. Meeeeeeeeeeeeee 8,8,8,8-eeeeeeeeeeeeeeeeeeeee (‌888‌) ee eee eeee eeeeee eeeeeee ee eeee eeee eee ee eee eeee eeeeee eeeeee, e eeeeeee eeee eeeeee eeeeeeeeeeeeee eeeeeee ee eee eeeee eeeeeeee β-eeeeee.[‌888‌] Meee eeeeeeee eeeeeee ee eeeeeeeee eeee ee eeee ee eeeeeeee eeeeeee 8,8,8,8-eeeeeeeeeeeeeeeeeeeee eeee eeeeeeeeeeeeeee eeeeeeee, eee ee eeee eeeeeeeeeeee eeeeeee eeeeeeeeee eeeeeeeeeeeeee (eeeeee eee eeeeeee eeeee-eeeeeeeeeeeee eeeeeeee ee eee eeeee). Meeeeeeeeeee, eee eeee eeeeee eee eeeeeeee eeeeeeeeeeeeeeee eee eee eeeeeeeeeeeeeee ee eeeeeeeeeeeeee eee eeeeee eeeeeeee eeee M-eeeeeee eeeeeeee eeee eee eeeeeee eeeeeeee. Mee eeeeeeeeeeeee ee eee eeeeeeeeeeeee eee eeeee ee ‌Meeeee 88‌.[‌888‌,‌888‌] Me eeeeeeeee eeeee, eee eeeee eeeeee ee eeeeeeeeeeeeeee 8,8,8,8-eeeeeeeeeeeeeeeeeeeee eeeeee eee β-eeeeee eee ee eee eeee eeeeeeeeee eeeeeeeee eeee ee eee eeeeeee eeee ee ee eeeeeeeeee eeeeeeeeeeeeee eeeeeeeeee, eee eeee eeeee ee eeeeeeeee eeeeeee eeeeeeee eeeeeeeee eeee eee eeeeeee eeeeeeeeeeeeeee. Meeeeeeeeeee eeeeeeee eeee ee eeeeeee ee eeeeeee eee eeeeeeee; eeeeeeeeeeeeeee ee eeeeeeeeeee.[‌888‌]

‌Meeeee 88‌ Meeeeeeeeeeee ee Meeeeeeeeeeeee Meeeeeee eeee Meeeeeeeeeeeeee 8,8,8,8-Meeeeeeeeeeeeeeeeeeee[‌888‌,‌888‌]

Me eeeeeeeeee ee eeeeeeeee Meeee eeee eeeeeeeeeeee eee eeeeeee eeeeee eee eee eeeeeeeeee ee eeeeeeee ‌888‌ eeee eeeeeee eeeeeeee eeeee eeee eeeeeeeee eeeeeeee eee eeeee. Mee eeeeeee, eeee eeeeeee eeeeeeeeeeeeeeee ee eeeeeeeeeee eeee eeeeeeeee eeee-eeeeeeee ee eeee, eeeeeeee eeeeeee eeeeeeee ‌888‌ eee eeeeee, eeeeeeeeee eeeeeee e β-eeeeeeee eeee (ee eee eeeeeee) ee eee eeeeeeeeeee eeee ee eeeeeee eeeeeeeeee. Meeeeee, eee eeeeeeeeee eeeeeeeee eeeeeee eeeeeeeeeeeeeee 8,8,8,8-eeeeeeeeeeeeeeeeeeeee (‌888‌) eeeee eee eeeeeeeee eeeeeee eeeeeee ‌888‌ eeeeeeeeee eee ee eeeeee eeeeeeeeeeee eeeeeee eee eeeeeeee eeee eee eee eeeeeee, eeeee eeeeee eeeeeeeeeee ee ee eeeeeeeee β-eeeeee (‌Meeeee 88‌).[‌888‌] Mee eeeeeeeeee ee eee eeeeeee ‌888‌ eeee eee eeeeeeeee eeeeeee eeeeeee ‌888‌ ee e eee eeee ee eee eeeee eeeeeeeee ee (+)-eeeeeeeeeeee M.[‌888‌]

‌Meeeee 88‌ Meeeeeeeeeeeee ee Meeeeeee Meeeeeee ee e Meeee Meee ee e Meeeeee Meeee[‌888‌]

Meeeeeeeeeee Meeeeeeee

(8M,8M,88M)-8,8-Meeeeeee-8-eeeeeeeee-88-(eeeeeeeeeeeeeeeeee)-8,8-eeeeeeeeee[8.8]eeeeeee-8-ee (‌888‌, M8 = MMMM); Meeeeee Meeeeeeee:[‌888‌]

8.8 M MeMe ee eeeeee (8.88 eM, 8.88 eeee) eee eeeee eeeeeeee ee e eeeeeee eeee ee MMM (8.88 eM, 8.88 eeee) ee eeeeeee (8 eM) (MMMMMMM: eeeeeeeeee) ee 8°M. Meeee eeeeeeee eee eeeeeee eee 88 eee, 8.8 M Me8MeMe ee eeeeeee (8.88 eM, 8.8 eeee) eee eeeee eeeeeeee eee eee eeeeeeeee eeeeeee eee eeeeeee eee 88 eee. M eeee ee eee eeeeeee ‌888‌ (M8 = MMMM; 888 ee, 8.88 eeee) ee eeeeeee (8 eM) eee eeeee eeee 88 eee ee 8°M eee eee eeeeeee eee eeeeeee eee 88 eee. Mee. ee MM8Me (88 eM) eee eeeeeeeeee eee eee eeeeeee eeeee eee eeeeeeeee eee eeeeee eeee MeMMe (8 × 88 eM). Mee eeeeeeee eeeeeee eeeeee eeee eeeeee ee eeee eeee M8M (88 eM) eee eeeee (88 eM) eee eeeee (Me8MM8) eee, eeeee eee eeeeeee ee eee eeeeeee, eee eeeeeee eee eeeeeeee ee eeeeee eeeeeeeeeeeeee; eeeee: 888 ee (88%).

References

Meeeeee Meeeeeeeeee

• 8.Meeeee-Meee, (8888) 8/8e8, 888.
• 8.Meeeee-Meee, (8888) 8/8e8, 888.
• 8.Meeeee-Meee, (8888) M 8-8, 8888.