Acetal formation, from pentaerythritol

Acetal formation from pentaerythritol and benzaldehyde, 38, 65 Acetamide, 31, 17 Acetamide, N-bromo, 31,17 a-PHENYL-, 32, 92 Acetanilide, cz-benzoyl-, 37, 2 a -ben zoyl-2-mcth oxy-4-ni tro, 37, 4 Acetic acid, benzoyl-, ethyl ester, 37, 3, 32... 

These reactions often lead to cyclic acetals that interfere with the formation of high molecular weight products. Useful polyacetals, however, can be formed from pentaerythritol and acetals of di aldehydes ... 

A typical flow diagram for pentaerythritol production is shown in Figure 2. The main concern in mixing is to avoid loss of temperature control in this exothermic reaction, which can lead to excessive by-product formation and/or reduced yields of pentaerythritol (55,58,59). The reaction time depends on the reaction temperature and may vary from about 0.5 to 4 h at final temperatures of about 65 and 35°C, respectively. The reactor product, neutralized with acetic or formic acid, is then stripped of excess formaldehyde and water to produce a highly concentrated solution of pentaerythritol reaction products. This is then cooled under carefully controlled crystallization conditions so that the crystals can be readily separated from the Hquors by subsequent filtration. 

Coxon and Stoddart have directed their attention to the formation of penta-erythritol-derived cryptands. With these molecules, the strategy was to block one pair of hydroxyl groups as an acetal and form a crown from the remaining diol. In the first of the two reports cited above, this was accomplished by treating the 0-benzylidine derivative of pentaerythritol with base and diethylene glycol ditosylate. The crown was then treated with a mixture of UAIH4 and BF3 which gives partial reduction of the acetal as shown in (8.9), above. The monoprotected diol could now be treated in a fashion similar to that previously described and the benzyloxy cryptand (77) would result. The scheme is illustrated below as Eq. (8.10). 

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