Phenyl and pentafluorophenyl substiuted 1, 3-dio-xolan 2, 4-diones

Abstract

A series of phenyl and pentafluorophenyl substituted 1, 3-
dioxolan 2,4-diones (a-hydroxy carboxylic acid anhydrocarboxy—
lates) has been prepared by the reaction of phosgene with the
copper(II) salt of the appropriate a—-hydroxy carboxylic acid and
the potential use of such cyclic compounds as precursors in
the synthesis of poly-α-esters investigated.

The kinetic behaviour during thermal decomposition of
this anhydrocarboxylate series in non-hydroxylic solvents has
been studied with particular reference to polymer formation. The
reactivity of the anhydrocarboxylates to weak nucleophiles such
as alcohols may be adequately explained in terms of the steric
and electronic effects associated with both the anhydrocarboxylate
and the attacking nucleophile. The solvent in this bimolecular
reaction with alcohols exerts a considerable effect on the rate
of reaction.

The effect of a pentafluorophenyl substituent on the reactivity
and polymerisability of the cyclic monomer has been investigated.
The results indicate that the effect of a flueroaromatic substituent,
unlike many other polymerisations, is to increase the polymerisability
of the monomer.

The use of tertiary (aprotic) base initiators such as pyridine
offers a low temperature synthetic route to poly-a-esters. The
ease of polymerisation by this hitherto unexplored method is
determined primarily by the size of the substituents on the monomer and the extent to which those substituents may activate the ring
to nucleophilic attack. The unusual kinetic behaviour exhibited
by this type of reaction is explained in terms of the initial
formation of a charge-transfer complex between monomer and
initiator and subsequent decomposition to yield a polymerisable
species.

A number of substituted poly-a-esters have been prepared,
including the two optically active forms of the polymer in one case,
and some physical properties briefly examined. The primary
object of the work, however, was the elucidation of polymerisation
mechanisms rather than the preparation of high molecular weight
polymer.

Date of Award	1972
Original language	English