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Dependence of Product Stereochemistry on the Relative Concentration of Substrate in an NADH Model Reaction.

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York 1959, S.
Yu. N.
/2/ a) J.
246; b ) Neuere tleispiele: V.
Porshnev. Russ. Chem. Rev.
2
Becker, C. Wentrup, E. Katz, K.-P.
/3/ P.-W.
hochalin.
Am, Chem. SOC.
103 (19Bl),
Yanp, N. Yasunami, K.
ed by the metal ion species employed as catalyst.
We now wish to describe some dynamic aspects of the ste-
Zeller,
reochemistry observed in the present NADH model reduction.
(1980). 5110; b ) L. T. Scott, PI. A.
Chem. SOC,
Kirns, J.
8.
(1977). 530.
The substrate
5875.
2
rode1 reductant
Takase, Tetrahedron Lett%
-
1971, 1275.
(1.0 nnnole) was reduced with
1
an
equimolar
in the presence of magnesium perchlorate
-
(0.5 m o l e ) in dry acetonitrile (20 ml) at O'C for 5
60min.
The e.e. of the product ethyl mandelate was plotted against
/4/ Rhnlich laQt sich zeigen, daO das zuriickgewonnene 1-Phe-
the reaction period.
As shown in Figure 1, characteristic of
nylazulen nach wie vor vollstandip an Cl markiert ist.
Die isomeren Phenylnaphthaline enthalten die l3C-Anre1cherung jeweils an dam C-Atom, das auch die Phenylpruppe
00
m
trEpt.
Cham. socc
97
rr
(1975), 2931
/6/ a) N. J.
g
5
-90
m. J. S. Oeuar, S. Kirschner, 3. Am.
/5/
-70
S. Oewar, 5. Kirschner, 3. Am.
(1975). 2932; b ) J.
Aihara, Bull. Chem.
97
Japan 2
*.
n
Chem. SOC,
SOC.
m
$
-50
m
(1977), 1788; c) zusammenfassunp: m. Christl, ~ngeur.
Chm* 93 (198l), 515; AnQeW. Chern.
(1981).
Int. Ed.
End.
m
2
t30
I
529.
I
20
30
40
50
reaction period (min)
10
Eingegangen am 25. Januar 1982 /Z 112 S/
Figure 1.
60
Dependence of %e.e. of E-mandelate
on the reaction conversion.
the present aaynmetric system was the observation that the
e.e.
of the reduction product E-mandelate increased as
reaction proceeded. A similar increase in e.e.
the
with the con-
version by the use of chiral NADH models has been reported in
other examples /2a, b/. and was reasonably accounted for
-
-
1020
-
1022
-
terms of the feedback effect of the oxidized NA which
to be cited as
Angew. Chem. Suppi.
7982,1021-1027
zu zitieren als
Angew. Chem. Suppi.
7982,1021-1027
0 Valap Chemie GmbH, D-6940 Weinheim.1982
07214227/82/0606-1021S022.50/0
cumulated during the conversion:
in
the oxidized form
ac-
a,
a good
+
-3
P
4
Dependence of Product Stereochemistry on the Relative
Concentration of Substrate in an NADH Model Reaction
By Naomichi Baba, Jun'ichi Oda, and Yuzo Inouye"
Asyrmnetric synthesis with chiral NADH model compounds
has
been of keen interest and a number of important findings about the factors which affect the stereospecificity of
model reactions have been accumulated.
/1/ that an NADH model
&
the
Recently, we found
carrying L-prolinamide as a chiral-
ity-inducing center reduced ethyl benzoylformate
2
to
give
electron acceptor/3/, interacts with the reduced form
transfer attraction.
Such an interaction may bring
about a
specific blockage of one of the diastereotopic faces of dihydropyridine nucleus by virtue of the chirality used, per-
H
, r
Q
mitting an easier access of the substrate carbonyl
CONH2
to
the
unhindered faces and thereby contributing much towards im-
iH2Ph
proving the e.e. at the later stage of the reduction.
-h
2
through a chelative mediation of metal ion and/or a charge
2
Emandelate in 83% enantiomeric excess(e.e.)
and that
the
atereochemiatry of the reduction product was greatly affect-
The
higher enantioselectivity of such a complex as ;i formed
by
the feedback of the oxidized form in situ was evidenced
by
the initial addition of the oxidized form/2b/ as well as the
external addition of either chiral or achiral aromatics capa-
*
Prof. Dr. Yuzo InOUye, Dipl. Chem. Dr. Jun'ichi Oda,
ble of chelating and/or CT-complexing/2c/.
D I . Naomichi Baba.
the specific blockage of diastereotopic faces of dihydropyri-
Institute for Chemical Research,
Kyoto University, Uji, Kyoto, Japan
-
1021
-
This view
that
dine nucleus is an essential factor for higher enantioselec-
-
1023
-
tivity is cogently supported by the high optical yield found
for the self-irmnolative asymnetric reduction with a 4-methylsubstituted dihydronicot'inamide derivative/4/, where
/1/ N. Baba, J. Oda, Y. Inouye, J. Chem. SOC. Chem. Comun.,
1980, 815.
_
.
/2/ a) A. Ohno, T. Kimura, S. Oka, Y . Ohnishi, Tetrahedron
the
transfer of hydrogen from dihydropyridine to substrate carbon-
Lett., 1978, 757.
yl is of necessity feasible only at the face of hydrogen
J. Oda, Y . Inouye, J. Chem. SOC. Perkin Trans. I.,
Thus, the overall e.e.
vailable.
should increase
as
a-
7.
the
second component process becomes important due tothe progress
b) T. Makino, T. Nunoeawa, N. Baba,
Tetrahedron Lett.,
1979, 1683.
/3/ B. Pullman. A. Pullman, Proc. Nat. Acad. Sci.
of conversion.
U.S.,
(1959) 136.
J. Ludowieg. A. Levy, ~iochemis+ry,2,
the basis of reasonable assumptions predicts the dependence
(1964) 373.
G.
of e.e. on the initial concentration of the substrate
1977, 3325.
The equation /5/ derived by the kinetic consideration on
tive to that of the model reductant
&
rela-
in the present system.
A series of asymmetric reductions were conducted using
ethyl benzoylformate at relative concentrations of 0.1
m o l e s to the reductant
2
-
1.0
acetonitrile at 50°C for 100 min.
The e.e.'s
of
found
for
SOC., 101, (1979) 7036.
the
tration of the substrate (Figure 21,
Saito, A. K. Colter, Tetrahedron Lett.,
/5/ The feedback mechanism is expressed by the equations,
dry
resulted E-mandelate were plotted against the initial concen-
A
+
B
+ S k 2 2 C + Pi
A
+ C
/5/ in e.e. from 46 to 76% was in fact observed. This consti-
S
A
A
C
+
p,
B
where, A, C, B , S and P denote magnesium ion-activated/b/
chiral NADH model
In accord with the prediction, a significant increment
45,
/4/ A. Ohno, M. peguchi, T. Kimura, S. Oka, J. Amer. Chem.
(1.0 mole) in the presence of 0.8
m o l e of anhydrous magnesium perchlorate in 10 ml
1980,
c) T. Makino, T. Nunozawa, N. Baba, J. Oda, Y. Inouye,
mediate
5,
2,
4,
oxidized form
substrate
p
hypothetical inter-
and products respectively.
The
overall e.e. is given by the following equation derived
tutes the first example in which dependence ofproductstereo-
by mathematical treatments based on the reasonable ki-
chemistry on the initial concentration of substrate was shown
netic assumptions.
and received a kinetic justification in a non-rigorous
way.
%e.e. = (m-n)K+m-(n-m)JK(l-S/So)-lln[ (S/So +K) (l+K)-'l
Although only one example was presented here, it seems very
likely that in other asymnetric systems too a similar feedback interaction of reaction productfs) with reactant(s1 may
-
1024
where, m and n represent %optical yield of P1 and P2
respectively and + m by the assumption.
-
and K = k3(kl-k3)-'.
J = k1(kl-k3)-'
1026 -
The equation shows that the
e.e.
should rise monotonically when the initial concentration
So is increased and the reaction
a
m
leaving
70-
is nearly finished up
In
S at a lower concentration, SOD.
addition,
rt
the increase in e.e. with the decrease in
I
progress of reaction is also predicted by the equation
r
60-
S
due to
the
and found (Figure 1).
m
:
/6/ A. Ohno, H. Yamamoto, T. Okamoto, S. Oka, Y. Ohnishi,
50-
Bull. Chem. SOC. Japan.,
so,
(1977) 2385.
8'
Received June 10, 1981 /Z 102
I
I
I
I
0.2
0.4
0.6
0.8
1.0
concentration of ethyl benzoylformate
(mmole/lO ml, CH3CN)
Figure 2.
Mpendence of %e.e.
on the initial concen-
tration of ethyl benzoylformate relative
&.
to the model
sometimes be operative.
Accordingly, it might possibly
be
used as a probe for study of reaction mechanism together with
kinetic means.
We wish to express our thanks to Drs.
Mkm~&e_dqea@nt:
Nobuyuki Sugita and Tadashi O k a m t o for their helpful advices
in the kinetic treatments.
-
1025
-
-
1027 -
S/
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