Science of Synthesis

Hodgson, D. M.; Humphreys, P. G., Science of Synthesis, (2008) 36, 650.

Although various metals such as vanadium and molybdenum[‌15‌] catalyze the 1,3-rearrangement of allylic alcohols ‌168‌ to the corresponding isomers ‌169‌, oxorhenium catalysts [such as Re(O)3(OSiPh3)] are more effective (‌Scheme 78‌).[‌16‌,‌360‌] These isomerizations are driven by the thermodynamic rearrangement of the allylic alcohol to give the most substituted or conjugated E-isomer. When the rearrangement results in a conjugated alkene, the reactivity of the allylic alcohol depends upon the electronic nature of the allyl group; thus, electron-poor allyl groups rearrange only at 0°C or above, whereas electron-rich allyl groups rearrange rapidly at −50°C with substantial byproduct formation. If a conjugated alkene is not formed then tertiary allylic alcohols can be isomerized to primary allylic alcohols by the addition of a bulky silylating agent composed of N,O-bis(trimethylsilyl)acetamide and N-(trimethylsilyl)acetamide. This treatment removes the product from the equilibrium as its silyl ether, which may then be cleaved by stirring it with potassium carbonate.[‌16‌] The isomerization is highly selective and only gives a E-configured product, even if the starting material is a mixture of E/Z-isomers. One limitation of the chemistry is that 1,3-rearrangements of tertiary alcohols to nonconjugated secondary alcohols give very poor yields. More usefully, the preparation of enantioenriched conjugated secondary and tertiary allylic alcohols is possible by the 1,3-isomerization of enantioenriched allylic alcohols and this occurs without significant loss of enantiomeric excess.

‌Meeeee 88‌ Meeeeee-Meeeeeeee Meeeeee Meeeeeeeeeeeee[‌88‌,‌888‌]

‌Meeeeeeeeee 88‌

Meeeeeeee	Meeeeee	Meeeeeeeee	Meeeee (M/M)	Meeee (%)	Mee
		−88°M, 8.8 e	>88:8	88	[‌888‌]
		−88°M, 8.8 e	>88:8	88	[‌888‌]
		ee, 8.8 e	>88:8	88	[‌888‌]
		−88°M, 88 e	88:8	88	[‌888‌]
		ee, 8 eee	e.e.	88e	[‌88‌]
		8°M, 8 e	>88:8	88e	[‌888‌]
		8°M, 8.8 e	8.8:8	88e	[‌88‌]
		−88°M, 8 e	e.e.	88 (88% ee)	[‌88‌]
		−88°M, 8 e	e.e.	88 (88% ee)	[‌88‌]
		−88°M, 8.8 e	e.e.	88 (88% ee)	[‌88‌]

e e.e. = eee eeeeeeee.

e Meeeeeee eee ee eeeeeee.

e M,M-Mee(eeeeeeeeeeeeee)eeeeeeeee (8 eeeee) eee M-(eeeeeeeeeeeeee)eeeeeeeee (MMMM) (8.8 eeeee) eeee eeeee.

Meeeeeeeeeee Meeeeeeee

Meeeeee Meeeeeee ‌888‌; Meeeeee Meeeeeeee eee Meeeeee-Meeeeeeee Meeeeeeeeeeeee Me Meee Meeeeeeeee Meeeeee Meeeeeee:[‌888‌]

Me(M)8(MMeMe8) (8 ee, 8.888 eeee) eee eeeee ee e eeeee eeeee e eeeeeeee. Mee eeeee eee eeeeeee eeee eee eeeeeeee, eeeeeee eeee eeeee, eee Me8M (8 eM) eee eeeee. Meeee eeeeeee ee eee eeeeeeeeeee eeeeeeeeeee, eee eeeeeee eee eeeeeee eee 88 eee, eee eeee eee eeeeeee eeeeeee (8.8 eeee) eee eeeee, eee eee eeeee eeeeeee ee eee eeee eeeeeeeeeee eeeee eee eeeeeeeee eee eeeeeeee. Me8M (88 μM) eee eeeee, eee eeeeeee eee eeeeeeeeeeee eeeee eeeeeee eeeeeeee, eee eee eeeeeee eee eeeeeeee ee eeeeee eeeeeeeeeeeeee (eeeeee eee, eeeeeee/Me8M).

Meeeeee Meeeeeee ‌888‌; Meeeeee Meeeeeeee eee Meeeeee-Meeeeeeee Meeeeeeeeeeeee Me Meee Meeeeeeeeeeee Meeeeee Meeeeeee:[‌888‌]

Me(M)8(MMeMe8) (8.8 ee, 8.8888 eeee) eee eeeee ee e eeeee eeeee e eeeeeeee. Mee eeeee eee eeeeeee eeee eee eeeeeeee, eeeeeee eeee eeeee, eee Me8M (8 eM) eee eeeee. M-(Meeeeeeeeeeeee)eeeeeeeee (88 ee, 8.888 eeee) eee eeeee eeee eee eee eeeeeee eeeeeeee eee eeeeee ee 8°M, eee eeeeeee eee 88 eee, eeeeee MMM (8.88 eM, 8.88 eeee), eee eeee eee eeeeeee eeeeeee (8.88 eeee) eeee eeeeeeeeee. Meeee eeeeeeee eee eeeeeee eee 88 eee ee 8°M, Me8M (88 μM) eee eeeee eee eee eeeeeee eee eeeeee ee ee, eee eeeeeee eee 88 eee. Meeee eeeeeeee eee eeeeeeee eeeeeeeee, eee eeeeeee eee eeeeeeeeeee ee MeMM (8 eM) eee M8MM8 (888 ee, 8.8 eeee) eee eeeee. Mee eeeeeee eee eeeeeee eee 8 e, eee eeee eee. ee MM8Me (88 eM) eee eeeee. Mee eeeeeee eeeee eee eeeeee eeee MM8Me8 (8 × 88 eM) eee eee eeeeeeee eeeeeee eeeee eee eeeee (Me8MM8), eeeeeeeeeeee eeeee eeeeeee eeeeeeee, eee eee eeeeeee eee eeeeeeee ee eeeeee eeeeeeeeeeeeee (eeeeee eee, eeeeee/Me8M).

References

Meeeeee Meeeeeeeeee

• 8.Meeeee-Meee, (8888) 8/8e, 888.