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Methods and Problems in the Study of Optically Active Polymers.

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at about 80°C, yielding compounds (17) and (16); on
cleavage with acetyl chloride the acetals (15) yield N-(chloromethy1)aniline derivatives (18) and carboxylic esters (19) ;
the compounds (18) with hydrogen cyanide afford cyanides
(20), with dimethylaniline afford diamines (21), and with
monosubstituted indanediones afford compounds of type
(22).
[VB 13 IE]
[Lecture at Marl o n June 15th, 19661
German version: Angew. Chem. 78, 828 (1966)
Racemization of atropisomeric model compounds is first
order, but the polymer racemizes appreciably more slowly
and not according to first-order kinetics.
Polymers of type (3), with atropisomeric groups in the main
chain, have been obtained by interfacial polycondensation of
(+)-l,l’-binaphthyL2,2’-diamine with terephthaloyl dichloride.
[Lecture at Mainz (Germany),
June 23rd, 19661
WB 16 IE]
German version: Angew. Chem. 78, 909 (1966)
Methods and Problems in the Study of Optically
Active Polymers
Chemistry of o-Quinol Acetates
F. Wessely, Vienna (Austria)
R . C. Schrrlz, Mainz (Germany)
For the preparation of optically active polymers asymmetric
monomers were polymerized with radical or ionic initiators
[e.g., menthol and borneol acrylate and methacrylate,
menthol N-vinylurethane, N-substituted N-(a-methylbenzy1)acrylamides, N-vinylureas derived from a-amino acids], and
asymmetric substituents were introduced into optically inactive polymers in polymer-analogous conversions.
High-molecular crystalline polyesters ( I ) with softening
points of about 170 “ C were obtained by ring-opening polymerization of L-dilactide:
Whereas, in all cases studied so far, reaction of o-quinot
acetates with K C N leads to m-hydroxybenzonitriles, reaction
of compound ( I ) with KCN depends on the solvent. It gives
a m-hydroxy nitrile ( l a ) only in dimethylformamide, formation of this product being explained by 1,6-addition to the
conjugated system of ( I ) . However, in methanol compound
(Ib) is formed, a result for which a complicated rearrangement must be responsible. Both reactions proceed rapidly at
room temperaturt.
OH
(lo), 60%
0
6HO
KCN
C HO
( I b ) , 70%
(1)
In this reaction the configurations of all the asymmetric C
atoms are retained and are the same, so that a completely
isotactic polymer results. The optical rotatory dispersion and
circular dichroism were measured in several solvents. The
Cotton effect, which is observed only for poly-r-lactide,
indicates a secondary structure. The rotatory dispersion can
be described equally well by the modified two-term Drude
equation and by the Moffit-Yang equation; the constants
are similar to those for helical proteins and poly-L-aminoacids, but the signs are reversed.
I
C02CH3
O n treatment of compound (2) with KCN the product is
practically independent of the solvent. The reaction leads to
conversion of the aldehyde group into a carboxyl group,
which can be esterified by the alcohol used as solvent.
0
*CH3
All optically active polymers described previously contain
asymmetric C atoms. However, treatment of (+)-2’-methyl6’-nitrobiphenyl-2-carbonylchloride with polyvinyl alcohol
yields the first polymer (2) whose optical activity is due to
atropisomerism.
This polymer gives the same Cotton effects as monomeric
model compounds.
The specific rotation of the polymer corresponds precisely to
the analytically determined content of atropisomeric substituents. From the rotatory dispersion and the circular dichroism it can be concluded that there is n o mutual optical
interaction between the side groups of this polymer, that
the polymer structure has no influence on the specific rotation, and that in solution the macromolecules are randomly
coiled.
850
H3C OzC
85%
For the mechanism of the reaction leading from ( I ) to (Ib)
it is important that the quinol acetate (3) and KCN in
methanol give a 55 % yield of compound (Su), whereas only
a very small yield of (3a) is obtained from the quinol acetate
(4) under the same conditions. The structure of compound
(3.) has resemblances to that of compound (lb).
Reaction of ( I ) and (2) with trimethylsilyl azide in methanol,
or with the azide ion, leads to compounds ( I c ) and (2a).
Quinol acetates carrying alkyl groups on C-4 or C-5 do not
give such products. Thus the azide ion adds to an o-quinol
acetate only if the latter is activated by a formyl group. The
Angew. Chem. internat. Edit. 1 Vol. 5 (1966) 1 No. 9
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