A range of novel chiral tellurium compounds having an azomethine
functional group in
the position ortho to tellurium has been synthesized by the
reaction of the tellurium-containing aldehydes bis(o-formylphenyl) telluride
(1) and o-(butyltelluro)benzaldehyde
(4)
with chiral amines (R)-(+)-(1-pheylethylamine) and
(1R,2S)-(−)-norephedrine,
respectively.
The precursor aldehydes were prepared by using a reported
procedure with slight but
advantageous modifications. During the preparation of
o-(butyltelluro)benzaldehyde,
interesting side products, namely bis(o-formylphenyl)
ditelluride ethylene acetal 5,
bis(o-formylphenyl) tritelluride (6), and
bis(o-formylphenyl) ditelluride (7) were
isolated in
moderate yields. The ditelluride 7 has been
characterized by single-crystal X-ray diffraction
studies. The liquid Schiff bases 10 and 11
were further characterized by derivatizing with
liquid bromine. The title compound was obtained in excellent yield
by reacting the Schiff
base 11 with elemental bromine. Detailed NMR studies
indicated the presence of a rigid
environment for the hydroxyl group. Single-crystal X-ray
determinations of the crystals
obtained from the different batches indicated the presence of the two
pseudopolymorphic
forms 13a and 13b, respectively. In the case
of 13a there is one molecule of CH3CN
as
solvent of crystallization, whereas in 13b half a molecule
of CH3CN per molecule of the title
compound lies along the 2-fold axis. In 13a the
hydroxyl hydrogen is hydrogen-bonded to
the nitrogen of the solvent molecule, whereas in 13b it is
hydrogen-bonded to the bromine
of the neighboring molecule.