Table 2. Scope for the C-2 arylation of indoles ^a .

^aReaction conditions: 0.5 to 1.0 mol% Pd(OAc)₂, 1.0 mmol heteroarene and 1.0 equiv. aryldiazonium salt in 5 mL EtOAc : 2-MeTHF (1 : 1) at rt, open flask, 2 h premixing of Pd(OAc)₂ with heteroarene.

^bPd₂(dba)₃ as catalyst, 1 h reaction.

^c1 mol% Pd(OAc)₂, 1.2 equiv. aryldiazonium salt.

^d4-Methoxybenzenediazonium mesylate was used.

^eGram-scale experiment (10.0 mmol) yielded 2.47 g (83%), 4 h reaction time in 2-MeTHF as solvent.

^f1 mol% Pd(OAc)₂.

^g2 mol% Pd(OAc)₂.

^h2 mol% Pd(OAc)₂, 1.2 equiv. aryldiazonium salt.

ⁱ1.2 equiv. aryldiazonium salt at 40 °C; *no full conversion obtained.

^j0.01 M and 100 mol% Pd₂(dba)₃ was used.