627-08-7

We report a new continuous method for forming ethers, acetals and ketals using solid acid catalysts, DELOXAN ASP or AMBERLYST 15, and supercritical fluid solvents. In the case of ether formation, we observe a high selectivity for linear alkyl ethers with little rearrangement to give branched ethers. Such rearrangement is common in conventional syntheses. Our approach is effective for a range of n-alcohols up to n-octanol and also for the secondary alcohol 2-propanol. In the reaction of phenol with an alkylating agent, the continuous reaction can be tuned to give preferential O- or C- alkylation with up to 49% O-alkylation with supercritical propene. We also investigate the synthesis of a range of cyclic ethers and show an improved method for the synthesis of THF from 1,4-butandiol under very mild conditions.

The bond reactivities for ethyl n-propyl ether, based on unity for the primary bonds of ethyl group, again prove the discriminate attack of methylene.All secondary bonds are attacked faster than the primary bonds of ethyl, the 2 C-H of ethyl itself being attacked 1.83 times, which is higher than the attack on secondary αC-H (1.74) and βC-H (1.29) bonds.The descending order of reactivities of C-H bonds in propyl is α > β > γ.Additional evidence of the electrophilic effect of ethereal oxygen on the insertion reactions as also on the displacement reaction where methylene gives a methyl alkyl ether and displaces an olefin has been obtained.Similarly, the predicted formation of aldehydes resulting from the abstraction reactions of methylene has been observed.These results obtained in gas phase contrasted with the liquid phase work of Doering et al who found the attack to be indiscriminate.This work further confirms the difference between the two phases.

Aliphatic primary alcohols, when intercalated in certain ion-exchanged montmorillonites, react preferentially via an intermolecular nucleophilic displacement of water to give high yields of di-(alk-1-yl) ethers, rather than the competitive intramolecular dehydration to alkenes; an essentially similar process yields polymeric material, poly(phenylenemethylene), from benzyl alcohol, but aliphatic secondary and tertiary alcohols, in contrast, yield alkenes almost exclusively.

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