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An Unusual Reaction of Fluorenone Hydrazones.

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absorption of ( I ) (23-27 x lo3 cm-1) and of (2) ( 2 G 2 4 x
lo3 cm-1)~ These new bands constitute the first evidence for
CT* absorption bands of an electron transfer from a T-excited donor to a n unoccupied energy level of an acceptor [21.
In the present communication we wish to report the results
of studies on a n electron transfer from the solvent dipropyl
ether (PE) as n-donor to the dissolved T-excited acceptors
( 3 ) or (4)131.
where I E ( D ) is the ionization energy of the solvated donor;
EA(A) and EA(A:) are the electron affinities of the solvated
acceptor in the ground state and the triplet excited state
respectively; E c is the coulombic interaction energy in the
ion pair [D' . . . A-l,o~v;EOO(SO + TI) is the T-excitation
energy of the acceptor; EA(A;) = EA(A) + Eoo(So + TI).
I E P E ) = 9.3 eV [7J;EA(3) = 0.55 eV and EA(4) = 0.85 eV [41;
Eoo(S0 + T i ) = 23 x lo3 cm-1 = 2.85 eV for ( 3 ) and ( 4 ) ;
EA(3j: = 3.4 eV; EA(4j; = 3.7 eV.
With ?CT = 29 x lo3 cm-l(3.6 eV) for the n,x complex (PE)tetracyanoethylene (5j, the relationship E c % ZE(PE) EA(5j - hvCT with EA(5) = 2.0 eV (41 gives E c = 3.1 eV. Insertion of these values into eq. (1) yields S C T ~ (PE) . (3); %
17.7 x lo3 and i j c ~ f ( P E.)(4); % 15.3 x 103 cm-1.
The GCT; values calculated in this manner lie - within the
limit of errors of such a n estimation - in the range of the
long wave CT* absorption band (Fig. 1: el, fl).
Tbe energy difference of the absorption bands (Fig. 1: el, ez
and fl, f2) show good agreement with the excitation energy
Eoo(T1 +Tz) of the acceptor (% 15 x lo3 cm-1). Thus it
may be supposed that the second absorption band (Fig. 1:
e2, f2) at shorter wavelength is also a CT* absorption band,
which can be calculated from
hvc$
=
+
~ V C T ; Eoo(T1+T2)
However, in view of the great errors of such rough estimations
a further detailed experimental study (e.g. polarization measurements) will be necessary.
I
l
l
r
.
l
l
l
20
15
Y
i
l
l
.
25
i10~crn-'1-
Fig. 1. Absorption spectra of triplet excited pyrornellitic dianhydride
( 4 ) and tetrachlorophthalic anhydride (3) in solvent glass.
a) ( 4 ) in PE (3 x 10-5 M), T = 100'K; b) (4) in BA (1.6 x
M),
T = 115 "K; c) (3) in PE (6 x 10-5 M), T = 100 OK; d) (3) in BA (1.4 x
10-4 M), T = 115 O K . e) difference between the spectra of ( 4 ) , a-b;
f) difference between the spectra of (31, c-d. Band width: 70 (short
wave region) to 200 cm-' (long wave region).
We compared the TT absorption spectra of ( 4 ) and (3j in
a solvent glass composed of 75 % butyl acetate, 19 % methylcyclohexane, and 6 % isopentane (BA) in the 12-27 x lo3
cm-1 region (Fig. 1 : b,d) with the corresponding spectra of
solutions in (PE) glass (Fig. 1: a,c): The main difference is
observed at ij < 17 x l o 3 cm-1 in a new, broad absorption
band (Fig. 1: a,c). Assuming that the spectra a,b and c,d are
equal, to a good approximation, in the TT absorption region
17-21 x lo3 cm-1 of (4)and 18-25 x lo3 cm-1 of ( 3 ) the
subtraction of the spectra in (PE) and (BA) affords two broad
unstructured absorption bands exhibiting no fine structure
(Fig. 1: e,f). The red shift of the maxima of these new double
bands in (PE) o n going from ( 3 ) to ( 4 ) corresponds to a n increase in the electron affinity of the acceptor from 0.55 to
0.85 eV [41.
If it is considered that the electron affinity of a T-excited acceptor molecule is higher than that in the ground state by a n
amount equal to the T-excitation energy [51, the longwave absorption band (Fig. 1, el, fl) of T-excited ( 3 ) and ( 4 ) in (PE)
can be interpreted as a CT* band of eIectron transfer from
(PE) as electron donor to T-excited ( 3 ) and ( 4 ) respectively:
Received: February 23, 1970
[Z 170 IEI
German version: Angew. Chem. 82, 356 (1970)
[*I Prof. Dr. G. Briegleb and Dr. H. Schuster
Institut fur Physikalische Chemie der Universitat
87 Wurzburg, Markusstrasse 9-1 1 (Germany)
[l] G . Briegleb, H. Schuster, and W . Herre, Chem. Physics
Letters 4, 53 (1969).
[21 G. Briegleb and H. Schuster, Angew. Chem. 81, 790 (1969);
Angew. Chem. internat. Edit. 8, 771 (1969).
[3] For further details see G . Briegkb and H. Schuster, Z . Naturforsch. n, to be published.
[41 G. Briegleb, Angew. Chem. 76, 326 (1964); Angew. Chem.
internat. Edit. 3 , 617 (1964).
IS] H. Leonhardt and A. Weller, Ber. Bunsenges. physik.
Chem. 67, 791 (1963).
[6] Studies connected with fluorescence quenching provided
evidence for a direct electron transfer without any need of hv
via intermolecular complex formation
of a singlet excited donor or acceptor molecule with an acceptor or donor molecule in the ground state. Cf., e.g., H. Knibbe,
D . Rehm, and A . Weller, Ber. Bunsenges. physik. Chem. 73,
839 (1969).
[7] R. W . Kiser: Tables of Ionization Potentials. Kansas State
Univ., Manhattan, Kansas 1962.
An Unusual Reaction of Fluorenone Hydrazones
By Joachim Gante and Giinther Mohr[*I
This would be the first observation of a C T absorption band
due to a n electron transfer from a donor to a triplet excited
acceptor molecule 161.
The energy of the CT* absorption can be estimated from:
370
Reaction of fluorenone hydrazone ( l a ) "1 and 2-chlorofluorenone hydrazone ( I b j 121 with ethyl chlorocarbonate in
anhydrous ethyl acetate in the presence of triethylamine
(molar ratio 1 : 1 : 1) did not yield the expected carbazates
but, instead, N,N',N"-tris(fluoreny1idenamino)guanidine ( 2 a )
(yield 46%, decomp. pt. 300"C, brownish red crystals) and
N,N',N"- tris(2-chlorofluoreny1idenamino)guanidine ( 2 b )
(yield 25 %, decomp. pt. 340 "C, brownish red crystals).
Angew. Chem. internat. Edit. 1 Vol. 9 (1970) No. 5
a) Thecondensation of (2) with ( I ) , (3), and ( 4 ) ,if necessary
via the Schiff base of (2) and ( 3 ) , should take place rapidly
and in high overall yield [21.
b) As a component of the condensation, ( 2 ) must also have
the effect of an asymmetrically inducing steric matrix and
provide for a highly stereoselective synthesis of the newly
formed amino acid unit in the desired configuration.
c) The residue R*must be readily cleaved from ( 5 ) under mild
conditions, e.g. in cold formic or trifluoroacetic acid, preferably in such a manner that ( 2 ) can be regenerated from (7).
(a), R = H
( b ) , R = C1
6".\
NH
Of all previously tested [21 amines ( 2 ) only those of type ( 2 a )
meet all the specifications (a)-(c) 14, 51.
g
R
AIH-
Fe
0
R
(2a) and ( 2 b ) are insoluble in almost all the usual organic
solvents. They may be recrystallized from dimethylformamide. The composition of (2a) and (2b) follows from analysis and the IR spectrum. Chemical evidence for the structure
was obtained by heating triaminoguanidine hydrochloride [31
with fluorenone (molar ratio 1 : 3) in ethanol/conc. hydrochloric acid (7 : 1) to give a product that was identical with
(2a) according to its IR spectrum and analysis.
Attempts to prepare compounds corresponding to (2a) and
(2b) by the same route from other hydrazones, such as benzaldehyde-, p-nitrobenzaldehyde-, and benzophenone hydrazone, proved unsuccessful; complicated mixtures were obtained instead.
-NH2
(2aj
Optically pure chiral ferrocene derivatives [**I with planar
and central chirality can be obtained via the stereoreIating[61
metalation of chiral tertiary a-ferrocenylalkylamines,as is
illustrated by the example of the synthesis of (IOa)-(lOe/
from (8). Both antipodes (8) can be readily obtained by
resolution of the racemate by (R)-(+)-tartaric acid [(8)-(S)(R)-tartrate from methanol, (8)-(R)(R)-tartrate from the
residue of the mother liquor by crystallization from acetonewater (10 : l)].
cH3
Received: March 12, 1970
[Z 177 IE]
German version: Angew. Chem. 82, 361 (1970)
[*I Priv.-Doz. Dr. J. Gante and Dr.
G. Mohr
Forschungslaboratorium der Firma E. Merck
61 Darmstadt, Frankfurter Strasse 250 (Germany)
[I] H . Wieland and A. Roseeu, Liebigs Ann. Chem. 381, 231
(1911).
[ 2 ] N . Latifand N . Mishriky, Canad. J. Chem. 42, 2893 (1964).
131 G . Pellizrari and A . Gaiter, Gazz. chim. ital. 44, 11, (1974).
Stereorelating Syntheses of Planar Chiroids
By Dieter Marqunrding, Hans Klusacek, George Gokel,
Peter Hoflmann, and Ivar Ugi [*I
The success of asymmetrically induced four component
peptide syntheses C1-31
R1
R3
R2
. . . .-NH-c%-co,H
+
+
NH,
I .a,
I
CHO
+ cN-~co-.
...
Re
(2)
( 1)
R'
1
-
R3
R2
I"-
li.
. . . .-NH-C~I-CO-N-CH-CO-NH-CH-CO-.
.. .
I,
+
(4)
(3)
(5)
R'
R3
R2
I:::
I "S
-NH-&-CO-NH-CH-CO-NH-CH-CO-... +
Bx
f 7)
(6)
depends appreciably upon the amine component ( 2 ) 131 which,
in this context, has to meet the following requirements:
Angew. Chem. internat. Edit.
1
Vol. 9 (1970)
No. 5
0
(IOaj - ( l o p )
The metalation of (8)-(R)
151 by n-butyllithium in ether leads
almost exclusively (Qpn = 96 : 4[71, by quantitative chromatography) to (9)-(R)(R)[61. The methyl group of the side
chain has to point "downward" when the (R)(S)-diastereomer of (9) is formed by a chelate mechanism[s*gJwith the
consequence that a n appreciable repulsive interaction with
the ferrocene system is witnessed.
The reactions of (9)-(R)(R)with alkylating agents (methyl
and ethyl iodide[9J, trimethylsilyl chloride[6l) or carbonyl
compounds (formaldehyde, benzophenone 161) produce (IOU)
to ( l O e ) .
( I O U ) : R = CH3 (after treatment of the reaction mixture
with dimethylamine), yield 66 %, chromatography o n A1203acetone/hexane (1 : 4), b.p. 104-105 OC/O.2 torr, [a]: =
+32.9 O , c = 2.4 (ethanol).
( l o b ) : R = C2H5 (after treatment of the reaction mixture
with dimethylamine), yield 47 %, b.p. 106-107 OCjO.2 torr,
[a]: = -16.2', c = 1.7 (ethanol).
f I 0 c ) : R = (CH3)3Si, yield 61%, Rf = 0.55 tNH3-treated
SiOz-ligroin/isopropanol(20 : l)] b.p. 103-104 "CjO.04 torr,
[a]',"= f15.5 ', c = 1.5 (ethanol).
(ZOd): R = HOCHz, yield 5 8 % , m.p. 1O9-11O0C (cyclohexane), [a]: = +121.5 ",c = 1.4 (chloroform).
(ZOe): R = HO(C6H&C, yield 52%, m.p. 118-119°C
(methanol), [a]: = -191.6 O , c = 0.5 (ethanol).
Since the amines of type ( I 0 1 are easily transformed (e.g. by
retentive s N 1 14.51 or eliminations 14991) into other ferrocene
37 1
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