Abstract
An efficient catalytic system was developed for the acetalization and ketalization of carbonyl compounds with polyhydric alcohols under mild solvent-free conditions. In the presence of 0.1 mol% CoCl2 and 0.2 mol% dimethylglyoxime at 70 °C under 5 KPa pressure for 1 h, 95.3% conversion of cyclohexanone and 100% selectivity of the corresponding cyclic ketal could be obtained, where TOF reached as high as 953 h−1. It is proposed that the in situ generated planartetracoordinate cobaloxime played the key role in the catalytic cycle and was responsible for the excellent catalytic performance.
Highlights
The protection of carbonyl groups plays an important role in multi-step organic synthesis ofcompounds with multiple functional groups
The most general method for the synthesis of acetals or ketals is the reaction of carbonyl compounds with an alcohol or diol
Many acid or Lewis acid-functionalized ionic liquids were used for acetalization or ketalization [21,22,23,24]
Summary
The protection of carbonyl groups plays an important role in multi-step organic synthesis ofcompounds with multiple functional groups. Acidic catalysts like protic acid [1,3,4], Lewis acid [5,6,7,8,9], and heteropoly acids [10] were used to synthesize acetals or ketals, and the removal of by-product water was essential. Those methods suffered from several drawbacks, such as corrosion, tedious work-up, environmental pollution and non-recoverability of catalysts. Many acid or Lewis acid-functionalized ionic liquids were used for acetalization or ketalization [21,22,23,24]
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