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available materials. We believe that our methodology
provides an effective entry to the synthesis of 2,5-diaryl-
heteropentalenes and will serve as a practical basis for
thorough SAR analyses as well as other synthetic appli-
cations of this class of compounds.
Acknowledgements
Drs S. G. Mills, J. J. Hale and V. J. Colandrea are grate-
fully acknowledged for valuable discussions.
2. For a thorough review on heteropentalene preparations,
see: Comprehensive Heterocyclic Chemistry; Katritzky, A.
R., Rees, C. W., Eds.; Pergamon: Oxford, 1984; Vols. 4
and 6.
3. In an unpublished study, we have investigated cyclizations
of more than twenty different N,N0-diarylhydrazides and
isolated 2,5-diaryl-1,3,4-thiadiazoles in yields heavily scat-
tered in a range of 5% and 95%. For an experimental
procedure used in the study, see: Tschierske, C.; Girdzi-
nuaite, D. J. Prakt. Chem. 1991, 333, 135.
Supplementary data
Supplementary data containing experimental proce-
dures and compound characterizations can be found in
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plings is
a reaction of 2-bromothiophene with a
corresponding phenylmetallic reagent. Our investigation
revealed that Negishi, Stille, and Suzuki couplings were
feasible under conditions of Methods A–C described in
Table 1. However, the generality of this approach did not
extend to some other heterocycles.