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Geometrical Dependence of [2+2]Photocycloaddition.

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dissolved in dichloromethane (20 ml) at 25°C whereupon
the color of the solution rapidly changes from yellow to dark
red. Solvent and liberated trimethylphosphane are removed
from the stirred solution in a vacuum. This procedure is
repeated several times and the residue finally washed twice
with lOml ether and then 10ml pentane. After drying in
a high vacuum, (2) is obtained as analytically pure, brick-red
crystals: yield 0 . 8 0 ~(83 %).
Received: November 12, 1976 [Z 602 IE]
German version: Angew. Chem 89. I10 (1977)
CAS Registry numbers:
( l ) , 60270-32-8: ( 2 ) . 61202-59-3; "P, 7723-14-0: ''C, 14762-74-4
F. R . Krri.\c/, A . Frorik, G'. Schirhrrt, T L. Limhier, and G. Hirttiier,
Angew. Chem. 88, 649 (1976); Angew. Chem. Int. Ed. Engl. 15, 632
( 1976).
E. 0. Fisthrr. T L. Lirid~ier.and F. R . Kreisrl. .I. Organomet. Chem.
112, C27 (1976).
F . R Krci\\/, M! L ' d d h o ~ ~and
i , K. Ehed, Chem. Ber., in press.
Analogous phenyl-, 4-methoxyphenyl-. mesityl-, and ferrocenyl-ketenes
have also been prepared and characterized [3].
Jeol C-60 HL..
Brukcr HFX 90, at 12.63 and 36.43 Hz.
Syntex-P2, : monoclinic. space group P2,;c: a=716.8. h = 1879.2,
( ' = 1508.7 pm, p = 1 15.5"; 977 independent diffraction data (1 2301. Solution: Syntcx-XTL, conventional, R , =0.06.
4 . 11. R i ~ h i i wand 1V A . lio.r.muiiii. Angew. Chem. 88. 652 (1976);
Angew Chem. Int. Ed. Engl. 1 5 , 615 (1976).
+
Geometrical Dependence of [2n 2 a]Photocycloaddition[**]
the correlation between /lvalues and photochemistry in the
cases of pentacyclo[6.3.1 .l 3,6.02.7.09.'
'Itridec-4-ene (6)"' and
endo-tetracyclo[5.2.1 .02~6.03~5]dec-8-ene[3!
The orbital energies (e= -lPi,,,) shown in Figure 1 are
derived, with the usual assumptions, from the vertical ionization potentials of (3)--(7) (Table 1). In the reference compound ( 5 ) , the transannular interaction (TAS =transannular
strain) between the n- and C-H bonds lowers IP1,, by 0.3 eV
(cf. IP2,,=8.90eV in (3)14]). The [j value in ( 4 ) (-0.45eV)'41
hardly differs from that of norbornadiene ( -0.4eV)151 and
is lowered by a similarly small amount on replacement of
a double bond by a three-membered ring ((6): /j= -0.37eV;
cf. exo-tricyclo[3.2.1 .02.4]oct-6-ene: p= -0.3 eV)[']. A similar
lowering by ca. 0.1 eV relative to the already smaller value
of the corresponding diene ( 8 ) (-0.2 eV)l3]makes the /j value
of the homodiene (9) (-0.1 eV) very small.
Table 1. Vertical ionization potentials ( I P L , v[eV]) of the hydro~arbons( 3 )
( 7 ) (values rounded off to the nearest 0.05eV).
JP,
IP2
x.45
8.90
8.10
9.35
8.60
9.70
IP3
8.80
9.70
IO.00
9.45
9.90
By Horst Prinzbach, Gotifried Sedelmeier, and Hans-Dieter
Martiri ['I
Photochemicalcycloadditionsoftype ( 1 ) - (2) ([2n+20])
are even more dependent upon the relative orientation of
the participating bonding orbitals than the analogous
[2 n 2 n] reactions[']. The p parameter as determined by
+
,,--_
.
Ly
PE spectroscopy can be considered as an experimental criterion for the assessment of these geometrical requirements;
the transannular overlap present in the "vertical" radical
cations is assumed to be typical of the photoreactivity of
the excited states. With this in mind we have investigated
13)
(4)
161
~
[*I
~
(-0
f 71
Fig. 1. Orbital correlation diagram for compounds ( 4 ) - 4 7 1 .
Direct irradiation of a ca. 3 x
M CH3CN solution of
(6) [i-:21~~,,,=2950;-35"C, 150W Hg high pressure lamp,
quartz vessel, 70 % conversion (96 h)] leads, according to GC,
1.05*9.08,'
* 1to a mixture (ca. 65 %) of hexacyclo[5.5.1 .0296.03s'
tridecane ( 1 0 ) (colorless crystals, m. p. 222 to 223 oC)'61and
the hydrogenation product (7) (m.p. z -20°C) which was
freed by chromatography (A1203,20 % A g N 0 3 ) from residual
(6) and polymeric material and isolated by G C (SE 30/10 %,
100°C; 27 and 23 % isolated, respectively, based on reacted
(6)).
-
Prof. Dr. H. Priiizbach and DipLChem. G. Sedelmeier
Lehrstuhl riir Organische Chemie der Universitlt
Albcrtstrasse 21. D-7800 Freiburg (Germany)
Prof. Dr. H.-D. Martin
lnstitut fiir Organische Chemie der Universitgt
Am Hubland. D-8700 Wurzburg (Germany)
Photochemical Transformations, Part 57. Part 56: H . Prinzhuilz and
H . Sriirrer, Tetrahedron Lett. 1974. 3049. Also: Small Rings, Part 21.--Part
20. H.-D. Morfiri. C . H r l l w , and R . W. f f o f l r n m i t i , Chem. Ber., in press.
[**I
/ ea
161
-
+
h'
17)
iIOi
Under the same conditions, the conversion of ( 9 )
[c22o=700] is comparably slow; in addition to polymeric
product, TLC and GC give no indication of (11)['1 but only
the progressive formation of the dihydro product ( 1 2 ) ; the
103
latter is isolated in ca. 55 % yield after complete consumption
of (9).
[2] Prepared by cyclopropanation of ( 4 [diazomethane. C'uBr, ether; after
total conversion 56% of (6) (1n.p. = 20°C) and 35%, of ( 1 6 ) (m.p. 7 8 ° C ~ :
separation on Al2O3120X, AgNO,.'n-pentane]. The structures of the
new compounds (61, 1 7 ) , (161, and ( 1 9 ) are confirmed by elemental
analysis and spectroscopic data (IR. UV, MS. 'H- and "C-NMR).
[ 3 ] H.-D. Morrin, S. Kogahu. and R. Srhxesniger, Chem. Ber. IU7. 3130
(1974).
[4] H.-D. M u r r i n and R. Schnwinger. Chem. Ber. 107, 3143 (1974).
[5] P. Bischof~E. Heilbronner. H . Prinzhach, and H . - D Murtin, Helv. Chim.
Acta 54. 1072 (1971).
[6] J. M . Brown. J . Chem. Soc. B1969, 868.
[7] t'. T McBrr, W L . Diliiriq, and H . P. Broeridiin, J. Org. C'hem. 27.
2704 (1962).
[8] H . Prin-bach and H.-D. Marrin, Helv. Chim. Acta 51, 438 (1968): A .
Brirggirik and H . Hogereen. Tetrahedron Lett. 1972. 4961.
The course of photolysis of (6) and ( 9 ) corresponds to
expectation in that at the very short wavelength of excitation
necessary [2 K 2 01 cycloaddition becomes effective against
the major competing reaction, hydrogenation, only under very
favorable overlap conditions, i. e. given a large /lparameter.
We expect to gain a more detailed insight from studies
of homodienes of type (13)--(15) with systematic variations
in distances and angles between the T [ / Gbonds.
Unstable Intermediates in the Gaseous Phase"]: The
Thermal Decomposition of Alkyl Sulfides RS,RIZJ
+
By Hans Bock and Shamsher Mohmarzdp]
Photoelectron spectrometers provide "finger prints" of
molecules in the form of ionization band patterns. PE spectra
are therefore especially suitable for the analysis of gaseous
reaction products and, hence, for the optimization of gas-phase
a)
In compound (16)''] formed as co-product on preparation
of (6) the stereochemistry is favorable for [2 G + 2 01 cycloaddition to form (18), a reaction already attempted on earlier
occasions. O n gas phase pyrolysis, (16) is stable up to ca.
HIC,
,C=CH,
HIC
500°C but polymerizes and chars above 750°C. However,
between 630 and 670°C the reaction affords an hydrocarbon
isomeric to (16) in 60-70%
yield together with a small
amount of side products [(18)?]. According to spectroscopic
data the hydrocarbon is not the highly symmetrical cycloadduct (18) but hexacyclo[6.5.1.02~6.03~1z.0s~10.09~13]tetradecane (19) (m.p. 199 to 200"C)-probably formed from the
intermediate ( I 7) by hydrogen migration.
d
Received: November 2, 1976 [Z 604 IE]
German version: Angew. Chem. 89, 1 1 1 (1977)
CAS Registry numbers:
( 3 ) . 15914-94-0; ( 4 ) , 1076-13-7; (Z), 1076-12-6: (61,61177-04-6;
( 7 ) - 61140-68-9; (81, 15564-45-1; (9), 30358-36-2; ( l o ) , 24856-73-3;
Fig. 1. PE spectra of di-tert-butyl sulfide (a) and its thermolysis products
up to 690 K (b and c) and at 1400 K (d).
(121. 53862-36-5; (16), 61 140-69-0; (18). 61140-70-3; ( 1 9 ) . 61248-60-0
-
[ I ] H . Prinzhach and D.Hunkier, Chem. Ber. 106,1804 (1973); and references
cited therein.
104
I*]
Prof. Dr. H. Bock and Dipl.-Chem. S. Mohmand
lnstitut fur Anorganische Chemie der Universitat
Theodor-Stern-Kai 7, D-6000 Frankfurt am Main 70 (Germany)
Angew. Cliem. l n t . Ed. Epgl. 16 ( 1 9 7 7 ) No. 2
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geometrical, dependence, photocycloaddition
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