Edward S. Rothman

Enol esters XIII: Synthesis of isopropenyl esters by addition of carboxylic acids to propyne

The addition of long chain carboxylic acids to propyne under conditions of elevated temperature and pressure takes place in the presence of the zinc salt of the corresponding acid as indicated by the following equation. The reactor apparatus is described and the properties of a series of enol esters are listed. this series shows examples with chain length variations of the carboxylic acid moiety of the ester from 8 to 22 carbon atoms.

Reactions of the stearoylated enolic form of acetone, involving hexadecylketene as the reactive intermediate

Enol esters, such as isopropenyl stearate, are useful intermediates capable of forming interesting derivatives of saturated aliphatic fatty acids. Under given conditions, whereas methyl stearate remains unreactive up to 400C, by contrast the isopropenyl stearate ester efficiently liberates hexadecylketene at 170C with the simultaneous expulsion of “isopropenyl alcohol,” i.e., acetone. In the presence of even difficulty acylatable OH or NH compounds the liberated aldoketene combines, usually quantitatively, with these hydrogen-bearing compounds to form esters or imides. In this manner such resistant materials as barbituric acids, hydantoins, N-butylstearamide, acetanilide, t-butyl alcohol, and succinimide may be converted to stearoylated derivatives.In the absence of reactable substrate and with strong dependence on the nature of the reaction medium, liberated hexadecylketene tetramerizes to derivatives ofgamma pyrone, or forms stearone, or stearoylates the enolic rearrangement product, heneicosane-2,4-dione. The latter compound, in forming, has increased the 18 carbon chain-length to 21 continuous carbon atoms. Di-isopropenyl esters with polyfunctional acetylatable materials, such as bis-N-alkylazelaamide or sucrose, give rise to unusual linear polyimides, three-dimensional network polymers, or oligomers.

Enol esters XVI: Enol ethers in synthesis

The synthesis of isopropenyl octadecyl ether is reported. This compound is a useful reagent for the synthesis of wax esters by reaction with long chain fatty acids, and of symmetrical or unsymmetrical ethers via reaction with long chain alcohols. The long chain alkyl isopropenyl ether is more sensitive to hydrolysis than the corresponding enol ester and forms successively the ketal 2,2-dioctadecyloxypropane, and octadecanol and acetone. Glycerol reacts with propyne yielding glycerol acetonide, glycerol acetonide isopropenyl ether and diglycerol bisacetonide. New crystalline derivatives of diglycerol are described, useful for the characterization of that substance.