reaction conditions by applying a lesser amount of Xantphos or
different ligand systems significantly decreased the yield or
proved to be completely unsuccessful (Table 1, entries 6−9).
Utilizing either Pd(OAc)2 or Xantphos yielded 0% of 3aa,
respectively (Table 1, entries 10 and 11). The use of air instead
of an oxygen atmosphere was less successful and afforded the
product in only 41% yield (Table 1, entry 12). Moreover, to
prevent triphenylene formation the slow or stepwise addition of
2a was not necessary. The catalytic system in combination with
phenyl thiocyanate bypasses this undesired reaction pathway.
Other common oxidants such as benzoquinone, silver
carbonate, and copper(II) acetate entirely suppressed the
product formation. Application of oxone and ammonium
persulfate had no influence on the reaction and afforded the
product in similar yields as when under an argon atmosphere.
With the optimized reaction conditions in hand we started to
examine the scope of this transformation (Scheme 2).