J.-L. Mieusset et al. / Tetrahedron Letters 54 (2013) 681–683
683
Scheme 3. Photolytic decomposition of oxodiazirine 1 entrapped within the cavities of two a-cyclodextrins.
the least affected peak. Every proton of 1 experienced a downfield
Supplementary data
shift due to deshielding. In contrast to the guest’s signals, those of
the cyclodextrin host were not well separated. The peak arising
from the anomeric proton H-1 was not shifted much and the low-
est field signals at dH = 3.9 ppm and 3.6 ppm were moved upfield.15
Nothing could be determined about the other peaks in the region
due to overlap.
Supplementary data (these include experimental methods for
the gas-phase pyrolysis of 1 and the preparation and photolysis
of the
a
-cyclodextrin complex 1@(6-Cy)2. Also included are 1H
and 13C NMR spectra of compounds 1, 3, 5, and 6) associated with
The variation in dH for the peak at dH = 1.6 was used to prepare
the Job plot depicted in Figure 1. The data show an extrapolated
maximum at
v = 0.33, which entails a 1:2 guest-to-host ratio, or
References and notes
1@(6-Cy)2. This was the reactant used for further investigation,
as shown in Scheme 3 3.
1. For reviews, see the following: (a) Mieusset, J.-L.; Brinker, U. H. In Molecular
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The inclusion complex 1@(6-Cy)2 was prepared and photolyzed
according to the procedures outlined in Supplementary data sec-
tion. After workup, the 1H NMR spectrum revealed much tricyclic
ketone 3 but very little alkenone 4 (Scheme 3 3): 7% 4 and 93% 3.
Supramolecular constraint of oxodiazirine 1 within the confines
of the a-cyclodextrin ‘dimer’ had a dramatic effect with regard to
which intramolecular pathway the reaction took.11 When
compared with the ca. 1:1 ratio found in the gas phase, the con-
densed phase ratio of 93:7 represents a sharp increase in product
selectivity. Formation of tricyclic ketone 3 via 1,3-CH insertion
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The inhibition of the skeletal rearrangement led to a purer product
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ˇ
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a
dextrin to steer a reaction toward one pathway demonstrates
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tion of 1 entrapped within the cavities of two
a-cyclodextrins
(i.e., 1@(6-Cy)2). The former method showed no particular
preference for ketone 3 or 4 (i.e., ratio = ca. 1:1) whereas a
marked contrast in the product ratio was observed when the
latter technique was applied (i.e., ratio = 93:7). These results
clearly demonstrate that even highly reactive intermediates,
such as carbenes, can be controlled when they are generated
within host containers.
ˇ
13. Mieusset, J.-L.; Krois, D.; Pacar, M.; Brecker, L.; Giester, G.; Brinker, U. H. Org.
Acknowledgments
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We thank Ms. S. Felsinger of the Institute of Organic Chemistry
of the University of Vienna for recording the 2D NMR spectra and
Ing. P. Unteregger of the Mass Spectrometry Centre of the
University of Vienna for recording the HRMS.