Lithiation of Oxy-Arenes; New Methodology for Electrophilic Aromatic Substitutions: Attempted Synthesis of Thiaheptalenes and Heterocyclic Pyrene Systems
Lithiation of oxy-arenes was studied. The lithiation of 4-hydroxyphenanthrene with 2 eq. of n-butyllithium/TMEDA in cyclohexane at 23(DEGREES)C occurs completely at the 5-position, although the 5-position is the most hindered position in the 4-hydroxyphenanthrene. By contrast, the lithiation of 4-methoxyphenanthrene by 1 eq. of n-BuLi/TMEDA in cyclohexane at 23(DEGREES)C occurs exclusively at the 3 position. Similarly, lithiation of (alpha)-naphthol under the same reaction condition gave 8-position lithiation and 2-hydroxybiphenyl was lithiated at the 2'-position. New reagents, 1,2-dibromo- and 1,2-dichloro-tetrafluoroethane were used for the halogenation of the lithiated positions. These remote lithiation reactions are useful in the synthesis of theoretically interesting heterocyclic heptalene and pyrene systems.
University of Illinois - Urbana-Champaign
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University of Illinois at Urbana-Champaign