At the outset of our studies phenyl thiocyanate (1a) and
aryne precursor 2a were reacted under standard conditions
commonly employed in aryne chemistry using CsF and
acetonitrile at 40 °C (Table 1, entry 1). As expected, even
after heating up to 80 °C, the desired coupling product could
not be detected, but complete consumption of 2a was observed.
Application of Pd(PPh3)4 as a catalyst yielded traces of product
3aa with concomitant formation of diphenylthioether as the
major product (Table 1, entry 2). Therefore, Pd(OAc)2 in
combination with Xantphos was applied affording 3aa in yields
varying between 10% and 30% (Table 1, entry 3). Surprisingly,
oxidative reaction conditions using an oxygen atmosphere
dramatically increased the yield to 81% (Table 1, entry 4). In
addition, the formation of diphenylthioether was suppressed
(