jo401807x_si_001.pdf (502.15 kB)
Oxidative Transformation to Naphthodithiophene and Thia[7]helicenes by Intramolecular Scholl Reaction of Substituted 1,2-Bis(2-thienyl)benzene Precursors
journal contribution
posted on 2013-11-15, 00:00 authored by Deepali Waghray, Christiaan de Vet, Konstantina Karypidou, Wim DehaenWe present here a strategy to synthesize
a variety of substituted
naphthodithiophene building blocks through DDQ/acid-mediated oxidative
cyclizations. The versatility of the Scholl reaction using the DDQ/acid
system was demonstrated by the preparation of a novel substituted
tetrathia[7]helicene where three new C–C bonds were formed
in a one-pot procedure. The new DDQ/acid method was compared to the
known strategies such as FeCl3 oxidation and oxidative
photocyclization. By protecting the 1,2-bis(2-thienyl)benzene precursors,
it is possible to direct the intermediates to controlled cyclization
and effectively suppressing the polymerization. The highly reactive
α-position of the terminal thiophenes can allow for further
functionalization. The efficient preparation of a variety of naphthodithiophene
building blocks, the extension to a nonphotochemical synthesis of
[n]helicenes, and the ease of isolation of the products
are arguments for the use of DDQ/acid system for this Scholl reaction.