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Novel Ring Opening of Hydroxyphenylcyclobutenedione.

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Novel Ring Opening of
By Wulter Ried and Gunter Isenbruck [*I
perature. The solution turns deep red and gradually becomes
cloudy. Precipitation is brought t o completion by stirring
for a few hours; the product is recrystallized from
DMF/CH,OH, yield 70-75 2;.
Received: March 9, 1970
[Z 176 IE]
German version: Angew. Cheni. 82, 807 (1970)
Publication delayed a t authors’ request
Dedicated to Professor H. Beyer on the occnsion of his
65th birthdny
( I ) reacts with
primary aromatic amines t o give 2-anilino-4-phenylcyclobutenediylium diolates 121, and with aliphatic amines t o give
ammonium salts which can be converted into the 2-amino4-phenylcyclobutenediylium diolates 131.
Compound ( I ) reacts with aromatic 1,2-diamines with loss
of H20 and 2 H t o give a red crystalline substancet41, whose
1R spectrum contains a carbonyl absorption at 1755 cm-1
indicative of a carbonyl group in a four or five membered
ring. If (2) is assumed t o have the structure given below, then
methylation of (20) with diazomethane must lead t o formation of (3).
The U V spectrum of (3) in C H 3 0 H shows absorption
maxima a t 229, 267, and 269, and a broad maximum at
323 nm (log E = 4.07) that is characteristic of pyrroloimidazole 151. 2,3 - Diphenylpyrrolo[l,2 - a]benzimidazol - 1 - one,
which is formed o n condensation of diphenylmaleic anhydride and o-phenylenediamine [61, also shows a broad
maximum at 325 n m (log E = 3.88) and a carbonyl absorption
a t 1755 cm-1.
According t o the spectra, elemental analysis, and molecular
weight determination (262), compound (2a) can be formulated as 3-hydroxy-2-phenylpyrrolo [1,2-a]benzimidazol1-one. Since hydroxyphenylmaleic anhydride does not react
under the conditions used for the preparation of (2) it
cannot be formed as intermediate. We suggest, therefore, the
following reaction mechanism.
[*I Prof. Dr. W. Ried und Dipl.-Chern. G . Isenbruck
Institut fur Organische Chemie der Universitzt
6 Frankfurt/Main, Robert-Mayer-Strasse 7 ~ - 9(Germany)
[**I Reactions of Cyclobutenediones, Part 16.
Part 15:
W. Ried and D. Schafer, Chern. Ber. 103, 2225 (1970).
[l] Part of the proposed Dissertation by G. lsenbruck.
[2] W. Ried, W. Kunkel, and G. lsenbrirck, Chem. Ber. 102,
2688 (1969).
[3] W . Ried, A . H. Schmidt, G. lseribruck, and F. Batz, to be
[4] W. Kunstmnnn, Dissertation, Universitst FrankfurtiM. 1969.
[5] C. A . Grob and P . Ankli, Helv. chirn. Acta 33. 658 (1959).
[6] A . Bistrz.ycki and K . Fassler, Helv. chim. Acta 6, 519 (1923).
Dependence of Solvatochromism on the Ground
State in 1,4-Heterobutadienecarbonylmolybdenum
By Heindirk tom Dieck and Ingo W . Renk 1 *I
T h e color of solutions of N,N’-di-tert-butyl-l,4-diazabutadienetetracarbonylmolybdenum ( I ) , as well a s of other 1,4diazabutadienecarbonylmetal complexes [I], depends considerably o n the polarity of the solvent (cf. Table) t21.
Strong solvatochromism is t o be expected when the ground
state of the dissolved complex is polar, i.e. when the polar
solvent molecules exhibit a high degree of short range order.
The excitation ought t o be antiparallel t o the ground-state
dipole moment VG since a particularly strong destabilizing
solvation then occurs in the excited state.
/I/, R=C1CH313
In complexes of Type ( I ) with CzVsymmetry the z-axis and
direction of p~ are coincident; in CzVboth are totally symmetric. Electron excitations in *z direction must have
ground and excited states of the same symmetry since with
the given symmetry of the z vector only the product of two
identical representations of Czv gives a totally symmetric
integrand of the transition moment and thereby a permitted
I n ( I ) the occupied metal d-orbitals fall into the symmetry
classes A*, Az, a n d B2. T h e lowest unoccupied orbital is 4 3
on the four-center x system which likewise has symmetry B2.
(Za); R
H ; (Zb) ; R
To a solution of ( I ) ( 5 mmoles, 870 mg) in glacial acetic acid
(30 ml) is added with stirring a solution of the diamine
(5-6 mmoles) in glacial acetic acid (20 ml) at room temAngew. Chem. internat. Edit.
Vol. 9 (1970) ,INo. I0
In Bz, metal a n d ligand orbital also have the strongest
overlapping which is of importance for the magnitude of
the interaction term and the intensity of the electron excitation.
According t o the values given in the Table, the longest
wavelength transition of (1) with extinctions between
12000 [cyclohexane) and 5000 1 mole-1 cm-1 (dimethyl
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opening, ring, hydroxyphenylcyclobutenedione, novem
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