Science of Synthesis

Wicha, J., Science of Synthesis, (2009) 48, 181.

Reduction of the 4-toluenesulfonate of an unhindered primary alcohol with lithium aluminum hydride gives the corresponding alkane in moderate to high yield; more information can be found in Houben–Weyl, Vol. 5/1a, p 544. A 3:1 mixture of lithium aluminum hydride and aluminum trichloride, which generates aluminum hydride,[‌78‌] can be used to deoxygenate 4-toluenesulfonates of primary allylic or benzylic alcohols via their derivatives with sulfur trioxide–pyridine complex.[‌75‌] The use of lithium aluminum hydride to deoxygenate sulfonate esters of sterically congested primary or secondary alcohols gives less satisfactory results. For example, reduction of the congested 4-toluenesulfonate ‌32‌ by lithium aluminum hydride gives the the parent alcohol in 25% yield (the yield of the deoxygenation product was not reported) (‌Scheme 26‌).[‌79‌] Cleavage of the O—S bond is the dominant process in the reduction of 4-toluenesulfonates of very sterically hindered alcohols.[‌80‌] Among the other metal hydrides that are readily available, lithium triethylborohydride has the highest hydrogen-transfer ability in reactions with sulfonate esters.[‌79‌,‌81‌,‌82‌] For example, the reduction of 4-toluenesulfonate ‌33‌ with lithium aluminum hydride in refluxing tetrahydrofuran/diethyl ether gives the product of substitution of the tosyloxy group with a hydrogen atom in 72% yield,[‌83‌] whereas reduction of the methanesulfonate ‌34‌ with lithium triethylborohydride (tetrahydrofuran/tert-butyl methyl ether, 0°C) gives the demesyloxylated product in 96% yield.[‌84‌] Lithium triethylborohydride permits the selective substitution of a hindered tosyloxy group with a hydrogen atom under mild conditions in the presence of other functional groups that are potentially labile to reducing reagents, as illustrated by deoxygenation of alcohol ‌35‌ to give ‌37‌ via 4-toluenesulfonate ‌36‌.[‌85‌]

‌Meeeee 88‌ Meeeeeeeeeeee ee Meeeeeee eee Meeee Meeeeeeee Meeeeeeeeee Meeee Meeeeee Meeeeeee Meeeeee ee Meeeeee Meeeeeeeeeeeeeeeeee[‌88‌,‌88‌–‌88‌]

Meeeeeeee ee eeeeeeeeee 8-eeeeeeeeeeeeeeee (‌88‌, M8 = Me) eeee eeeeeee eeeeeeee eeeeeee ee eeeeeeeeeeeeeee ee eeee eeeeeeeeeee eeeee e eeeeeee ee eeeeeeeeeee (88%), eeeeeeeeeee (88%), eee eeeeeeeeeeee (88%) (‌Meeeee 88‌),[‌88‌] eeeeeee eeee eeeeeee eeeeeeeeeeeeeeeeeee eeeee eeeeeee eeeeeeeeee ee eeeee eeeeeeeeeee (88%) eee eeeeeeeeeee (88%).[‌88‌] M eeeeeee eeeeeeeeee ee eeeeeeeee eee eeeeeeeeeee eeeeeeee ee eeeeeeee ee eeeeeeeee ee eeeeeeeeee eeeeeeeeeeeeeeee (‌88‌, M8 = Me) eeee eeeeeee eeeeeeeeeeeeeeeeeee, eee eee eeeeee eee eeeee (88 eee 88%, eeeeeeeeeeee).[‌88‌] Meeeeeeee eeee eeeeeee (eeeeeeeeeee-8,8-eeee)eeeeeeeeeeeeeeeee {Me[8-MMM(Me)M]} eeeee e eeeeeeee eeeeee eeeeeeeeee ee eee eeeeeeeee eeeeeee. Meeeeeee ee eeeeeeeeee eeeeeeeeeeeeeeee (‌88‌, M8 = Me) eeee eeeeeee eeeeeeeeeeeeeeeeeee, eeeeeeeee ee eeee eeee eeeeeee (eeeeeeeeeeeee)eeeeeeeeeee eee eeeeeeeeeeeeee, ee eeeeeeeeeeeeeee ee 88°M eeeee eeeeeeeeeee (88%) eeeeeeeeeee ee e eeeee eeeeee ee eeeeeeeeeee (8%).[‌88‌,‌88‌] Mee eeeeeee eeeeeeeeeeee ee eee eeeeeeeeeeeee eeeeeeee eeee eeeeeee ee eeee eeeeee ee eee eeeeeee eee eee eeeeeeeeeee.

‌Meeeee 88‌ Meeeeeeeeeeee ee Meeeeeeeee Meeeeeeeee ee Meeeeee Meeeeeee Meeeeee, Meeeeee Meeeeeeeeeeeeeeeeee, eee Meeeeee Meeeeeee[‌88‌,‌88‌,‌88‌]

‌Meeeeeeeeee 88‌

e Meeeeeee ee eeee eeee MeMM8MMe8 (8.8 eeeee) eee MMe8 (8.8 eeeee).

Mee eeeeeee eeeeeee ee eeeeeeeeee ee eeeeeee eeeeeeeeeeeeeeeeeee eeeeee eeeeeeee eeee eeeeee ee eeeeeee eeeeeeee ee eeeeeeeeeee ee eee eeeeeeee eeeeee ee ‌Meeee 8‌. Meee eee eeeeeeeeee eeee eeee ee eeeeeeeee ee eeeeeeeeee 8-eeeeeeeeeeeeeeee.

‌Meeee 8‌ Meeeeee Meeeeeeeeeee ee Meeeeee Meeeeeeeeeeeeeeeeee ee Meeeeeeeeeeee ee Meeeeeee eee Meeee Meeeeeeee Meeeee

e Me MM.

Meeeeeeeeee-eeeee-eeeeeeeeeeeee eeeeeee eee eeeeeeeee ee eee eeeeeeeee ee eeeeeee eeeeeeeeeeeeeeeeeee eeee eeee-8-eeeeeeeeeeeeeeeee eeeeeee eeee eeeeee eeeeeeeee eeeeee, eeeeeeeeeee, eee eeeeeee eeeeeeeeeee eeeeeeeee. Mee eeeeeeeeee ee eee eeeeeeee eeeeee ee eee eeeeeeee eeeeeeeeeeeee ee eee eeeeeeee eeeee eee eee eeeeeeeee eeeeeee eeeeee, eee eeeeee ee eee eeeeeeeeee eeeeee, eee eeeee eeeeeee. Meeeeeeeeee, eeeeee eeeeeeeeeeee ee eee eeeeeeee eeeee ee eeeeeee eee, eeeeeee eeee eeeeeee, eeeeeeeeeee eeee eeeeeeeeeee, ee eeeeeeeeeeeeee eeeeeee-eeeee eeeeeeeee eee eeeee.[‌88‌–‌88‌] Me eee eeee ee eeeee eeeeeeeee, eeeeeeeeeeeee eee ee eeeeeeeeeee ee eeeeeeeee ee eeeeeeeeeeeee eeeeee eee eeeeeeeeeee eeeeee eeee, ee eeeeeeeeeee ee eee eeeeeeeeeeeeee ee eeeee ‌88‌ eeee eeee ‌88‌ (‌Meeeee 88‌).[‌88‌–‌88‌]

‌Meeeee 88‌ Meeeeeeeeee-Meeee-Meeeeeeeeeeee Meeeeee ee Meeeeeeeeeeee ee e Meeeeeeeee[‌88‌]

Meeeeeeeeeee Meeeeeeee

Meeeeeeeeee (Meeee 8, Meeee 8); Meeeeee Meeeeeeee:[‌88‌]

MMMMMMM: Meeeeee eeeeeeeeeeeeeeeeeee (Meeee Meeeeee) eee eeeeee eeee eeeeeeee ee eeeeee eeeeeeee ee eee. Meee eeeeeee eeeeee ee eeeeeee eeee eee eeeeee eeee eeeee ee eeeee eeeeeeeeee eeee eeeeeeee eee eeeeeeeeeeee eeeeeeee.

M 8.8 M eeee ee MeMMe8M ee MMM (Meeee Meeeeee; 88.8 eM, 88 eeee) eee eeeee ee e eeee ee eeeeeeeeee 8-eeeeeeeeeeeeeeee (8.8 e, 88 eeee) ee eeeee MMM (88 eM), eeeeeee eeeee M8 ee 8°M. Mee eeeeeee eee eeeeeee ee ee eee 8 e eee eeee eee eeeeee ee eeeeeee eee eeeeeeeeee ee eeeeeeee eeeeeeee ee M8M. 8 M ee MeMM (88 eM) eee 88% M8M8 (88 eM) eeee eeeee ee eeeeeee eeeeeeeeeeee eeeeeeee. Mee eeee ee MMM eee eeeeeeeeee eeeee eeeeeee eeeeeeee eee eee eeeeeee eeee eee eeeeeeeee eeee eeeeeee (8 × 88 eM). Mee eeeeeeee eeeeeee eeeeeee eee eeeeee eeee M8M (8 × 88 eM) (ee eeeeee MeMM eeeeeeee ee eee eeeeeeeee) eee eeeee (MeMM8). Mee eeeeeeee eeeeeeee eeee eeeeeee ee eeeeeeeeeeee. Meeeeeeeeeee ee eee eeeeeee eeee eeeeeeeeeee (ee 888–888°M) eeeeeeeeee ee. 8% ee eeeeeeeeeee (ee MM); eeeee: 8.88 e (88%).

(8α,8α,8β,88M)-88-Meeee-8-eeeeeee-8,8-eeeeeeeeeeee-88-eee (‌88‌):[‌88‌]

MMMMMMM: Meeeeee eeeeeeeeeeeeeeeeeee (Meeee Meeeeee) eee eeeeee eeee eeeeeeee ee eeeeee eeeeeeee ee eee. Meee eeeeeee eeeeee ee eeeeeee eeee eee eeeeee eeee eeeee ee eeeee eeeeeeeeee eeee eeeeeeee eee eeeeeeeeeeee eeeeeeee.

MeMe (8.88 e, 8.88 eeee) eee eeeee ee eeeeeeee ee e eeeeeee eeee ee eeeeeee ‌88‌ (8.88 e, 8.88 eeee) ee MM8Me8 (88 eM) eeeeeeeeee eeeeeeee (8.88 eM, 88 eeee). Meeee 88 e, eee eeeeeee eee eeeeeeeeeee eeeeeee Me8M eee M8M. Mee eeeeeee eeeee eee eeeeee eeee Me8M, eee eee eeeeeeee eeeeeee eeeeeeee eeee eeeeee eeee eee. ee MM8Me. Mee eeeeeee eee eeeeeeeeee eee eee eeeeeee eee eeeeeeee ee eeeeeeeeeeeeee (eeeeee eee) ee eeee eee eeeeeeeeeeee 8-eeeeeeeeeeeeeeee ‌88‌; eeeee: 8.88 e (88%).

M 8 M eeee ee MeMMe8M ee MMM (88.8 eM, 88.8 eeee) eee eeeee eeeeeeee ee e eeeeeee eeee ee 8-eeeeeeeeeeeeeeee ‌88‌ (8.88 e, 8.88 eeee) ee MMM (88 eM) ee 8°M. Mee eeeeeee eee eeee ee ee eee 8 e eee eeee eeeeeeeeeee eeeeeee Me8M eee M8M. Mee eeeeeee eeeee eee eeeeee eeee Me8M, eee eeee eee eeeeeeee eeeeeee eeeeeeee eeee eeeeee eeee eee. ee MM8Me. Mee eeeeeee eee eeeeeeeeee eee eee eeeeeee eee eeeeeeee ee eeeeeeeeeeeeee (eeeeee eee); eeeee: 8.88 e (88%).

8′-Meeeeeeeeeeeee (‌88‌):[‌88‌,‌88‌]

MMMMMMM: Meeeeee eeeeeeeeeeeeeeeeeee (Meeee Meeeeee) eee eeeeee eeee eeeeeeee ee eeeeee eeeeeeee ee eee. Meee eeeeeee eeeeee ee eeeeeee eeee eee eeeeee eeee eeeee ee eeeee eeeeeeeeee eeee eeeeeeee eee eeeeeeeeeeee eeeeeeee.

M eeeeeee ee eeeeeeeee (‌88‌; 8.8 eeee), Me8MeM (888 ee, 8.8 eeee), eee eeeee MeMM (88 eM) eee eeeeeee eee eeeeeeee eeeee e eeeee eeee eee eeeeeeee (~8 e). Mee eeee eee eeeeee ee ee eee Me8M (8.8 eM, 88 eeee) eee eeeee eeeeeeee ee MeMe (8.88 e, 88 eeee). Mee eeeeeee eee eeeeeee eeeee eee eeeeeeee eeeeeeee eee eeeeeeee (~88 eee). Mee eeeeeee eee eeee eeeeeeeeee eee eee eeeeeee eee eeeeeeeeeee eeeeeee Me8M (88 eM) eee M8M (88 eM). Mee eeeeeee eeeeeee eee eeeeeeeeeeee eee eee eeeeeee eee eeeeeeeeeeeeee ee eeee eee eeeeeeeeeeee eeee-8-eeeeeeeeeeeeeeee; eeeee: 888 ee (88%).

M eeeeeee eeeeeeeee 8 M eeee ee MeMMe8M ee MMM (88 eM, 88 eeee) eee eeeee ee e eeeeeee eeee ee eee eeeeeeeeeeee eeee-8-eeeeeeeeeeeeeeee (888 ee, 8.88 eeee) ee eeeee MMMM (88 eM) eeeee M8 ee ee. Mee eeeeeee eee eeeeeee eee 88 e eee eeee M8M (8 eM) eee eeeeeeeeee eeeee. Mee eeee eee eeeeeeeeeeee eee eee eeeeeee eee eeeeeeee ee eeeeeeeeeeeeee [Meeee 8 × 8 (MM−), M8M] eee eeeeeeeeeeeeeee (MeMM); eeeee: 888 ee (88%).

References

Meeeeee Meeeeeeeeee

• 8.Meeeee-Meee, (8888) M 8e, 88.
• 8.Meeeee-Meee, (8888) M 8e8, 8888.
• 8.Meeeee-Meee, (8888) M 8e8, 8888.