| Abstract
| - The potentially chiral 7,8-dioxa[6]helicenes 1−1c have been prepared by oxidation of their precursorsthe 7a,14c-dihydro-7,8-dioxa[6]helicenes 3. The crystal structure determination of 3bcis-7a,14c-dihydro-3,12-dibromo-7,8-dioxa[6]helicene unambiguously confirms the cis configuration of the 7a,14c hydrogens in compounds 3 as previously implied from NMR measurements and also showsthat 3b crystallizes in a chiral conformation in the solid state. Selective deuteration of the stericallycrowded 1,14 positions of 7,8-dioxa[6]helicene 1 influenced the crystal structure. The deuteriumlabeled compound D2-1 exhibits a disordered structure, whereas 1 had been found to crystallize ina complex structure which can be described as an analogous partly ordered modulated superstructure. When dehydrogenation of compound 3 to obtain compound 1 was attempted, harsh syntheticconditions gave the unexpected halogenated compounds 5-chloro-7,8-dioxa[6]helicene 1c and cis-7a,14c-dibromo-7,8-dioxa[6]helicene 3c. Compounds 1d and 3b were identified by solving theircrystal structure.
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