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Non-Cheletropic Photodecarbonylation of 1 3-Diphenyl-Substituted 2-Indanone Derivatives.

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[ l ] This work was supported by Farbwerke Hoechst AG, the Deutsche
Forschungsgemeinschaft, and the Fonds der Chemischen Industrie.
[Z] R. Huisgen and H. Seidel, Tetrahedron Lett. 1964, 3381.
131 G. Quinkerr, K. Opitz, W.-W. Wiersdorff, and M. Finke, Tetrahedron Lett. 1965, 3009; Liebigs Ann. Chem. 693, 44 (1966).
[a] G. Quinkerr, W.-W. Wiersdorff, M. Finke, K . Opitz, and E-G. von
der Haar, Chem. Ber. 101, 2302 (1968).
(a), R = H
(b), R = CH,
(c), R = D
[ 5 ] G. Quinkert, M. Finke, 1.Palmowski, and W.- W. Wiersdorff, Mol.
Photochem. 1, 433 (1969).
[6] Performance and evaluation see K. H. Grellmann, E. Heilbronner,
P. Seiler, and A. Weller, J. Amer. Chem. SOC.90, 4238 (1968).
Ph H
[7a] The first portion of the curve shows the position of the base line,
upward (downward) deviations correspond to a decrease (increase) in
the transparency. 7 = temperature; t = sweep rate of trace; h =
wavelength at which decay curve was recorded; S = sensitivity ( Vo =
10 V);T = l/k. - The time-dependent photomultipliersignals Vo(before
flashing)and V = vf (at time f after flashing) are proportional to the intensity [of the signal. The change in optical density A E = A E ( f )is A E ( f )
= log IolJ = log vo/
[7b] Low-temperature spectroscopic data [4]: h,,, (E) = 284 (30600)
and 519 nm ( 9 1 7 0 ) , ~ ~ =~ 3.34;flashspectroscopicdataof
= 290 and 505 nm, E
~ ~= 3.3.
~ / E ~ ~
intensity: h,,
[8] See footnote 14 in IS].
191 The photo product obtained from (4) at -189°C [5] has an absorption maximum at 465 nm (E= 10600); warming to -178°C results
in an irreversible shift of the maximum to 455 nm without change in
intensity. This observation concerns that portion of the o-quinodimethane derivatives able to photocyclize and is compatible with a Z / E
isomerization of (8) to (7).
[lo] The quantitative results are based on the observation that the absorption of (6) at 455 nm has almost twice the intensity (20100) of that
of the other configurational isomers.
[ 1 la] The flash photolysis of (4) shows- apart from a slight participation
of (6) - analogous behavior.
[ 1Ib] According to low-temperature spectroscopic (flash spectroscopic)
data recorded in methyicyclohexane/3-methylpentane,4 : 1 (methylcyclohexane), the long wavelength absorption maximum of the thermally
most labile o-quinodimethane derivative (6) unable to photocyclize [5]
appears at 455 nm 191 (450 nm at 21.6"C); (7) shows a maximum at
455 (445) nm.
112) G. Quinkert, H.-P. Lorenz, and W.-W. Wiersdorff, Chem. Ber.
102, 1597 (1969).
Conversion Hydrocarbon fraction [a] Ketone fraction [a]
Ratio of isomers (Ye)
Ratio of isomers (%)
[13] G. Quinkerf, J. Palmowski, H.-P. Lorenz, W.-W. Wiersdorff, and
M. Finke, Angew. Chem. 83,210 (1971); Angew. Chem. internat. Edit.
Non-Cheletropic Photodecarbonylation of 1,3Diphenyl-Substituted 2-Indanone Derivatives"]
By Gerhard Quinkert, Joachim Palmowski, Hans-Peter Lorenz,
Walter- Wielant Wiersdorff, and Manfred Finkel']
Unconjugated cyclopentenones undergo smooth decarbonylation, both in their electronic ground state['] and after x * c n
t o give butadiene derivatives. If the thermal
decarbonylation proceeds in o n e step, the correlation diagrams
demand a stereospecific, in the present case disrotatory,
c o ~ r s e [ ~ ~T h~e~ ]stereochemistry
of the corresponding
photodecarbonylation, which has been discussed under different, in part contradictory, premises, is a przori unclear. Two
shortcomings a r e responsible for this, vjz. insufficient knowledge of the photoreactive state and lack of a conclusive theory
of light-induced reactions.
so so
R Ph
Ph R
( l a ) : 87, (2aJ: 13
( l a / .58; @a) 42
( l a ) 36; (20) 64
(3aJ. 8; (4a): 92
13a) : 10; (4aJ-90
m a ) : 11; (5a): 89
10, 198 (1971).
[ 141 In this case compound (7), which occurs in the same way, was de= 450 nm).
termined only flash spectroscopically (A,
1 ;;
100 Ib]
100 [b]
(3a) : 18; (4a). 82
(30) : 17; (4a). 83
(3a): 13; (40). 87
(3b) : 69;
(3b) : 70;
(36). 69;
(36) : 29;
exclusively (20)
(4b). 31
(46): 30
(461: 31
(4b): 12; (8J.59
(3bJ . 8; (46): 92
(36) : 10; (4b): 90
exclusively ( l b )
exclusively (Zb)
[a] The irradiation products were analyzed by gas chromatography IS]
and by NMR spectroscopy [ 121after treatment with an excess of LiAIH,
and chromatographicseparation of the alcohols from the hydrocarbons;
no effect o n the conversion
the presence of piperylene ( 0 . 7 5 ~ showed
and the product composition.
[b] Irradiation at -78°C.
T h e Table contains data of the decarbonylation of (la), (lb),
(a), and (Zb)[" in a merry-go-round apparatus[']. In each case
a mixture of configurational isomers of four-membered ring
hydrocarbons (3) and (4) occur, the composition of which
remains unaffected by the presence of the ketone triplet quencher piperylene. Simulation of a trivial non-stereospecificity by
photostereomutation of the benzocyclobutene derivatives does
not occur in direct irradiation or sensitization["]; in contrast
to ( l a ) a light-induced configurational isomerization of the ketonic reactants (lb), (Za), and (Zb) does not come into consideration. Although it has been established, for example, that (3a)
Angew. Chem. internat. Edit. / Voi. 10 (1971) / N o . 3
and (4a) are formed stereospecifically['21 from the corresponding seco isomers also detected a t room temperature"'], a thermal and/or photo configurational isomerization of the intermediate compounds under these conditionscannot b e ruled out.
T h e observed non-stereospecificity is therefore irrelevant for
the course of the reaction in question. However, the fact that
photostereornutation and photodecarbonylation in (la) result
from one and the same electronically excited singlet state verifies the stepwise, noncheletropic character of the light-induced
CO elimination in the case of the cyclopent-3-en-1-one system
investigated" '1.
Received December 23, 1970 [Z 344b IE]
German version: Angew. Chem. 83, 210 (1971)
Prof. Dr. G. Quinkert [**I, Dr. J. Palmowski [**I,
Dr. H.-P. Lorenz [***I, Dr. W.-W. Wiersdorf [****I,
and Dr. M. Finke [*****I
Institut diir Organische Chemie der Technischen Universitat Braunschweig
[**I Present address: Institut fur Organische Chemie der Universitat
6 Frankfurt/M., Robert-Mayer-Str. 7-9 (Germany)
[***I Present address: Schering AG, Bergkamen (Germany)
[****I Present address: Badische Anilin- und Soda-Fabrik AG, Ludwigshafen (Germany)
[*****I Present address: Farbwerke Hoechst AG, Frankfurt-Hoechst
[I] This work was supported by Farbwerke HoechstAG, the Deutsche
Forschungsgemeinschaft, and the Fonds der Cbemischen Industrie.
[2] a) C E H. Allen, Chem. Rev. 37, 209 (1945); 62, 653 (1962);
b) J. E. Baldwin, Can. I. Chem. 44, 2051 (1966).
[3] a) L. D. Hess and 1.N. Pitts, jr., J. Amer. Chem. SOC.89, 1973
(1967); b) G. Quinkert, K. Opitz, W.-W. Wiersdodf, and J. Weinlich,
Tetrahedron Lett. 1963, 1863; c) B. Fuchs, Israel J. Chem. 6,511, 517
(1968); J. Chem. SOC.C 1968, 68.
[4] a) R. B. Woodward and R. Hoffmann, Angew. Chem. 81, 797
(1969); Angew. Chem. internat. Edit. 8, 781 (1969); Science 167, 825
(1970); b) D. M. Lemal and S. D. McGregor, J. Amer. Chem. SOC.88,
1335 (1966); c) H.-P. Lorem, Dissertation, Technische Universitat
Braunschweig 1968.
tion, of molecular motion. Investigations carried o u t a t the
Weizmann Ir1stitute[*,~1suggest that the crystalline phase is a
suitable medium for photoelirninations as it allows entry of light
and escape of gaseous products.
A considerable increase of the cage effect, and consequently
of the constitutional selectivity, is observed for the
photodecarbonylation of 1,1,3-triphenyl-2-pr0panone[~~l
substituting the crystalline phase for the (benzene) solution. T h e
extent of the cage effect given by the ratio:
By Gerhard Quinkert, Taka0 Tabata, Eckhard A. J. Hickmann,
and Walter Dobrati']
T h e observation that photodecarbonylation of 1,3-diphenyl
substituted 2-indanone derivativesr2] does not take place in a
single step['] indicates a n intermediacy of biradicals, which, because of internal rotations and inversion a t radical centers comprise whole groups of subspecies. Experience has shown that in
such cases the preparatively as well a s mechanistically useful
product selectivity increases with increasing viscosity of the
medium[4]. T h e crystal lattice of a solid is expected t o have a
particularly strong influence o n the rate, and possibly the direc-
Angew. Chem. internat. Edit. / Vol. 10 (1971) / N o . 3
mde equivalent.
Ph -R
R Ph
(a), R = H
(b). R = CH,
(c), R = D
Table. Data of the decarbonylation of (la), (lb), (Za), and (2b)in solution and in the crystalline phase.
Percentage composition in
Solution [a]
Cryst. phase [b]
(3a): 13
(4a) : 87
Increase in Selectivity of Photoelimination Products on Replacing the Liquid Phase by the Crystalline Phase[']
increases from t h e one limiting value a = 0 in solution
(1,2-diphenylethane, 1,1,2-triphenylethane, and 1,1,2,2-tetrat o the other limiting
phenylethane occur in the ratio 1 :2 :
value a = 1 in t h e solid (1,1,2-triphenylethane is formed exclusively). T h e constitutional selectivity for the photodenitrogenation of diphenylmethylazotoluene changes less drastically;
practically only 1,1,2-triphenylethane occurs in the light-induced N, elimination in the crystalline phase a t -196"C['],
while o n irradiation of a benzene solution a t 27°C a falls only
t o 0.28[81. 'This finding is in accordance with t h e higher kinetic
stability of an acyl radical relative to the isoelectronicdiazoalkyl
[ S ] G. Quinkert, H.-P.Lorenz, and W.- W. Wiersdorff, Chem. Ber. 102,
1517 (1969).
[6] G. Quinkert, M. Finke, J. Palmowski, and W.- W. Wiersdodf, Mol.
Photochem. 1, 433 (1969).
[7] For the analysis of the irradiation product regarding photocyclizable
and non-photocyclizable o-quinodimethane derivatives see [6].
[Sl See footnote 14 in Ref. [6).
[9] B. Bronsrerr, Diplomarbeit, Technische Universitat Braunschweig
[lo] Irradiation of mixtures of ( l c ) and (3a) or of (lc) and (4)with
313-nm light does not result in stereomutation of the hydrocarbonsused.
[ 111 K. H. Grellmann, J. Palmowski, and G. Quinkert, Angew. Chem.
83, 209 (1971); Angew. Chem. internat. Edit. 10, 196 (1971).
[I21 G. Quinkerf, K. Opitz, W.-W. Wiersdorff and M. F i n k , Liebigs
Ann. Chem. 639,44 (1966).
[13] Premise for positive conclusions from quencher experiments: If
the energy hypersurface contains several triplet conformations they all
must be quenchable.
1; M
Oaj. 5
(4a) 95
(36) : 69
(4b) : 31
(4bj: 4
(5): 6
(3b): 9
146) .91
(36) : 14
(4bj: 86
[a] The products obtained by irradiation of an ethereal solution at
13i 2°C with 313-nm light were analyzed by gas chromatography I121
and by NMR spectroscopy[Zb] after treatment with an excess of LiAlH4
and subsequent chromatographic separation of the alcohols from the
[b] Irradiation was carried out in a Rayonet reactor (300-nm lamp;
Southern Ultraviolet Co., Middleton, Conn.) using afilter (2.5 % aqueous
solution of potassium hydrogen phthalate; layer thickness 8 mm) in a
Duran vessel of wall-thickness 1 mm at 13C 2°C. For a detailed analysis
of the irradiation products see [a]; in none of the cases was a stereomutation of the educt observed.
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indanone, cheletropic, photodecarbonylation, non, substituted, derivatives, diphenyl
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