An improved synthesis of 2,4,8,10-tetroxaspiro /5.5/ undecane /pentaerythritol diformal/

It is found that high yields of pentaerythritol diformal can be prepared in less than 10 minutes by heating a stirred mixture of pentaerythritol with a slight excess of paraformaldehyde up to about 120 C in the presence of catalic amounts of acid, but without any solvents or with only a small amount of water. The reaction was carried out in two stages: first by preparing the monoformal with a molar equivalent of paraformaldehyde in about five minutes, and then, after cooling to about 70 C, adding the remainder of paraformaldehyde in 1% excess, and heating to about 120 C for a total heating time of 10 minutes