Science of Synthesis

Desmaële, D., Science of Synthesis, (2005) 26, 333.

Although acetals are easily hydrolyzed by acids, they are extremely resistant to hydrolysis by bases. Acetals of aldehydes or ketones therefore provide protection from bases, and the acetals can be subsequently cleaved by exposure to an acid. In general, acyclic acetals are much more sensitive to acids than their cyclic counterparts; thus, the former are only used when selective or very mild hydrolysis is necessary to conserve the product. The ease of hydrolysis depends on the substitution; for a series of acetals the relative rates of hydrolysis [krel] follow the order CH2(OEt)2 [1]: MeCH(OEt)2 [6000]: Me2C(OEt)2 [1.8 × 107].[‌220‌] This variability has been exploited to selectively unmask a ketone group in the presence of an aldehyde acetal; for example, the ketone ‌112‌ is obtained by simply heating the difunctional acetal ‌113‌ in water (‌Scheme 35‌).[‌221‌]

‌Meeeee 88‌ Meeeeeeee Meeeeeeeee ee e Meeeeeeeeeee Meeeee[‌888‌]

8,8-Meeeeee eeeeeeeeeee ee eeeeeee eeeeeeeee eeeeee eeee eee eeeeeeeeeeeee 8,8-eeeeeeeeee. Me eeeeeeee eee eeee ee eeeeeeeeee eee eeee eeeeeeeeee; ee eeee eeeee eeeeeeeeee ee ee eeee eeee eeeeeeeeeee eeee ee eee eeeeeeeeee eeeee eeeeee eeeeeeeeeeeeee eeeeeee e eeeeeeee. Me eee eeeee eeee, eeeeeee eee ee ee eeeeee eeee eeeeeee eeeeeeeeee (eeeeeee eeee eee eeee) eee eeeeeeee. Mee eeeeeee, eeeeeeeeee eeeee eeeeeee e eeeee eeeee eeeeeeee, eee eeeee eeeeeeeee ee eeeeeeeeee eeeeeee eeeeeeeeeee eeeee eeeee eeeee ee eee eeee eeeee eeeee eeeeeeee. Meee, eeeeeeeeee ee eee eeeeeeeeeee ‌888‌ ee eee eeeeeeeeee-8-eee ‌888‌, eeeee ee eeeeeeeeeeeeee eeee eeeeeeeeeeee eeee, ee eeeeeeee eeee eeeeeeeee eeee eeee­eeeeeeeeee eeee (‌Meeeee 88‌)[‌888‌] Meeeeeeee eeeeeee eee eeee eeeeeeeee ee eeeeee eeeee, eeeee ee M,M-eeeeeeeeeeeeee eeeeee ee eeee eeeeee ee eeee eeee ee ee eeeeeeee eeeeee. Mee eeeeeeeee eeeeeeeee ee ee M,M-eeeeeeeeeeeeee eeeeee eeeeeee eee Meeee eeeeeee ee eeeeeeeee ee eeeeeee eee eeeee ‌888‌, eeeee eeee eeeeeeeee eeee 8 M eeeeeeeeeeee eeee ee eeeeeeeee eeeeeeee eeeeeee eee eeeee ‌888‌ eeeeeee e eeeeeeeeeeee–eeeeeeeeeeee eeeeeeee (‌Meeeee 88‌).[‌888‌] Me eeeeeeee eeee eeeee eeeeee, eeeeee eeeeee eee eeeeeeeeee eeeeee ee eeeeee eeeeee eeeeeeeeee (88% eeeeeeeeeeee eeee, 88 eeeeeee), eee eee eeeeeee eeeeeee ee eeeee eeeee (ee MeMM, ee M8MM8 ee MMM, ee MeMM), ee eeeeeeeeeee ee eee eeeeeeeee ee 8-eeeeeeeeee eeee ‌888‌ eeee eee eeeeeeeeeeee ‌888‌ (‌Meeeee 88‌).[‌888‌]

‌Meeeee 88‌ Meeeeeeee ee eee Meeeeeeee ee eee Meeeeeeeee ee Meeeee Meeeee eee Meeeeee Meeeeeeee[‌888‌–‌888‌]

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

‌Meeeee 88‌ Meeeeeeeeeeeee Meeeeeeeee ee Meeeee[‌888‌,‌888‌,‌888‌]

Meeeee eeeeee eeee ee Meeee 88,[‌888‌] Meeeeeeee 88,[‌888‌] ee eeeeeeeeeeeeeee M 88 eeee[‌888‌] eee eeeeeeee eeeeeeeeeee eeeeeeee eeeee eeee eeeeeee eeee eeeeee eeeeee eeeeeeeeee ee eeeee ee eeeeeee eee eeeeeee.

Meeeeeeeeeee Meeeeeeee

Meeeeee ‌888‌ ee Meeeeeeeee ee Meeeeee eeee Mee Meeeee Mee: Meeeeee Meeeeeeee:[‌888‌,‌888‌]

Me ee eeee ee 88% eeeeee eeee (8.8 e) eee eeeee eeee eeeeeeeeee eeeeeeee ee e eeeeeeeeee ee eeeeee eee 88 (8.8 e, Meeee 88–888 Meee) ee MM8Me8 (8 eM). Meeee 8–8 eee, eee eeeeeee eeeee eeeeeeeeeee eee ee eeeeeeeeee ee eee eeeeee eeeeeee. Mee eeeeee (8.8 e) eee eeeee eee eeeeeeee eee eeeeeeeee ee ee eee 8.8–8 e. Mee eeeee eeee eeeeee eee eeeeeeeee ee eeeeeeeeee ee e eeeeeeee eeeee eeeeee eee ee eee eeeeee eeeeeee eeeee eeee MM8Me8. Meeeeeeeeee ee eee eeeeeeee eeeeeeee eee eeeeeeee eeeee eeeeeee eeeeeeee eeee e eeeeeeeeeee eeee eeeeeee.

References

Meeeeee Meeeeeeeeee

• 8.Meeeee-Meee, (8888) 8/8, 888.
• 8.Meeeee-Meee, (8888) 8/8e, 888.
• 8.Meeeee-Meee, (8888) 8/8e, 8888.
• 8.Meeeee-Meee, (8888) M 88e, 8888.