(Z)-2,2′-disubstituted bifluorenylidenes by intramolecular desulfurdimerization reactions
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AbstractW(CO)6-mediated intramolecular desulfurdimerization reactions have been used in the syntheses of bridged 2,2′-disubstituted bifluorenylidenes in satisfactory yields. Ring sizes from 12 to 24 can be synthesized by this reaction. The extension of this reaction for the synthesis of bifluorenylidene-hinged crown ethers is described. The X-ray structure of 6i has been determined. The two fluorenylidene moieties are each planar, making a dihedral angle of 44.9°. The first optically active bifluorenylidenes were unequivocally synthesized, and the barriers for the racemization of two such molecules have been determined (12 kcal/mol). The racemization process may arise from the pyramidalization at C9 and/or C9′ followed by rapid twisting along the C9-C9′ bond. © 1990 American Chemical Society.
All Author(s) ListYip Y.C., Wang X.-J., Ng D.K.P., Mak T.C.W., Chiang P., Luh T.-Y.
Journal nameJournal of Organic Chemistry
Volume Number55
Issue Number6
PublisherAmerican Chemical Society
Place of PublicationUnited States
Pages1881 - 1889
LanguagesEnglish-United Kingdom

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