ORGANIC
LETTERS
2007
Vol. 9, No. 1
113-115
Cope Rearrangement versus a Novel
Tandem Retro-Diels Alder Diels Alder
Reaction with Role Reversal†
−
−
−
Kuan-Jen Su, Jean-Luc Mieusset, Vladimir B. Arion,‡ Lothar Brecker, and
Udo H. Brinker*
Institut fu¨r Organische Chemie, UniVersita¨t Wien, Wa¨hringer Strasse 38, A-1090 Wien,
Austria, and Institut fu¨r Anorganische Chemie, UniVersita¨t Wien,
Wa¨hringer Strasse 42, A-1090 Wien, Austria
udo.brinker@uniVie.ac.at
Received November 2, 2006
ABSTRACT
A reinvestigation of the thermolysis of 4,4-dibromotetracyclo[6.2.1.02,7.03,5]undec-9-ene (2) affords diene 8 with a completely rearranged
hydrocarbon skeleton via the isolable intermediate 4, along with cyclopentadiene and bromobenzene. DFT calculations show that the novel
tandem retro-Diels−Alder−Diels−Alder reaction with role reversal is slightly less favored than the overall single-step Cope rearrangement.
Organic chemists have always been fascinated by rearrange-
ments in which relatively simple compounds are being
transformed into more complex structures. The rigorous
clarification of the detailed reaction mechanism for such
conversions remains a challenging task.
According to an earlier report,1 heating of 4,4-dibromotetra-
cyclo[6.2.1.02,7.03,5]undec-9-ene (2), the product resulting
from a dibromocarbene addition to dicyclopentadiene (1), 2
at 130 °C for 1 h leads to the ring-opened3 compound 4
(Scheme 1). In addition, cyclopentadiene (5) and bromoben-
zene (7)4 are formed. A reinvestigation of the thermolysis
of 2, however, finds rac-(1R,2S,6R,7R,10R)-1,10-dibromotri-
cyclo[5.2.2.02,6]undeca-3,8-diene (8, 33% isolated yield), 5,
and 7 (42%, via GC calibration) as products. Moreover, 8
comprises 1H NMR and IR data identical with those reported
for 4.
A single-crystal X-ray analysis of 2 confirms the structure
of the starting material (Figure 2). Next, 2 was thermolized
in refluxing m-xylene (138 - 139 °C). In order to monitor
the thermolysis, every hour a sample for GC analysis was
taken. In Figure 1, peak areas of relevant signals are plotted
against reaction time.
* Corresponding author. Phone: +43-1-4277-52121. Fax: +43-1-4277-
52140.
† Carbene Rearrangements. 67. For part 66, see: Mieusset, J.-L.; Brinker,
U. H. J. Org. Chem., 2007, 72, 268.
‡ Institut fu¨r Anorganische Chemie.
The decrease of starting material 2 is unimolecular and
obeys first-order kinetics. The ring-opening product 4 is an
intermediate in the formation of final product 8. The
experiments were also performed at 111 °C with toluene as
(1) Molchanov, A. P.; Pecheritsyna, Ya. P.; Kostikov, R. R. J. Org. Chem.
USSR (Engl. Transl.) 1989, 25, 1076; Zh. Org. Khim. 1989, 25, 1195.
(2) (a) Ting, X.-T.; Liu, C.-P. Youji Huaxue 1988, 8, 511. (b) Huang,
N.-J.; Xu, L-H. Chin. Sci. Bull. 1991, 36, 831. (c) Zhao, Q.; Han, N.; Lin,
H; Yang, M. Huaxue Tongbao 2005, 68, w058/1.
(3) (a) Weber, J.; Xu, L.; Brinker, U. H. Tetrahedron Lett. 1992, 33,
4537. (b) Weber, J.; Brinker, U. H. Angew. Chem., Int. Ed. Engl. 1997, 36,
1623. (c) Wagner, R. A.; Weber, J.; Brinker, U. H. Chem. Lett. 2000, 246.
(4) Slobodin, Ya. M.; Ashkinazi, L. A.; Shustareva, T. K. J. Org. Chem.
USSR (Engl. Transl.), 1984, 19, 1787; Zh. Org. Khim. 1983, 19, 2062.
10.1021/ol0626793 CCC: $37.00
© 2007 American Chemical Society
Published on Web 12/13/2006