Science of Synthesis

Landais, Y.; Vincent, J. M., Science of Synthesis, (2005) 26, 667.

Hydrolysis of α-oxo ketals under mild, acidic conditions is a general method that provides the desired 1,2-diketones in consistently high yield. Acids such as formic acid (e.g., conversion of ‌93‌ into ‌94‌, ‌Scheme 26‌),[‌64‌] hydrochloric acid,[‌65‌,‌66‌] and 4-toluenesulfonic acid[‌67‌,‌68‌] are typically employed, either in water or in a mixture of water and acetone, tetrahydrofuran, or methanol. The hydrolysis proceeds at room temperature or under reflux. These conditions are compatible with most functional groups as illustrated in ‌Scheme 26‌. Mixed α-oxo ketals ‌96‌ are prepared in one step through coupling of 1,2-diethoxy-1,2-bis(trimethylsiloxy)ethene (‌95‌) with an acyl chloride under Lewis acid catalysis.[‌65‌] Mild hydrolysis of ‌96‌ then leads to 1,2-diketones ‌97‌ in high yield. An example of the use of hydrochloric acid is shown for the formation of 1,2-diketone ‌99‌ from dimethyl acetal ‌98‌.[‌66‌]

‌Meeeee 88‌ Meee-Meeeeeeee Meeeeeeeee ee α-Mee Meeeee[‌88‌–‌88‌]

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8-(Meeeeeeeeeeeee)eeeeeee-8,8-eeeee (‌88‌); Meeeeee Meeeeeeee:[‌88‌]

M eeeeeee ee 8,8-eeeeeeeee-8-(eeeeeeeeeeeeee)eeeeee-8-eee (‌88‌; 8.88 e, 88.8 eeee) eee 8 M MMe (8 eM) ee M8M (888 eM) eee eeeeeee eee eeeeeeee eee 8 e. Meee, eee eeeeeee eee eeeeee ee ee eee eeeeeeeee eeee Me8M (8 × 888 eM). Mee eeeeeeee eeee eee eeeeee eeee M8M (888 eM), eee. ee MeMMM8 (888 eM), eee eeeee (888 eM), eeeee (MeMM8), eee eee eeeeeee eee eeeeeeeeeeee ee eeeee ee eeee ‌88‌, eeeee eee eeee ee eee eeee eeee eeeeeee eeeeeee eeeeeeeeeeee; eeeee: 8.88 e (88%); MM (eeee) ν̃eee: 8888, 8888, 8888 ee−8.

References

Meeeeee Meeeeeeeeee

• 8.Meeeee-Meee, (8888) 8/8e, 888.
• 8.Meeeee-Meee, (8888) M 88e8, 888.
• 8.Meeeee-Meee, (8888) M 88-8, 8888.
• 8.Meeeee-Meee, (8888) M 88-8, 8888.