An unprecedented approach for the synthesis of imine derivatives was achieved via a Pd(II)-catalyzed dearomatization reaction of N-aryl ureas with internal alkynes. The corresponding spirocyclic imine derivatives were obtained with 20 examples in good to excellent yields. Mechanistic investigation indicated that an interesting 1,3-palladium migration process led to the α-regioselective dearomatization when 2-naphthyl ureas were used as the substrates. Fused ring products could also be obtained to further prove this migration process.

Selective meta-arylation of O-β-naphthyl carbamate has been accomplished using Pd(OAc)2 as a catalyst precursor and K2S2O8 with AgOAc as the oxidant. A range of aryl boronic acids could be introduced in moderate to good yields. Mechanistic investigation shows that the carbamate substituent has a unique effect and the reaction undergoes an ortho-carbometallation/meta-direct arylation process.

Palladium-catalyzed C–H direct arylation generally occurs on the ortho-position of directing groups. By comparing meta-arylated products of 2-naphthyl urea to ortho-arylated products of phenyl urea, the ortho- and meta-regioselectivity of aryl ureas were found to depend on the aromaticity of the corresponding aryl substituents. Thus, aromaticity is a new factor which can affect the regioselectivity in C–H direct arylation. The finding was further confirmed by regioselective direct arylation of indole and pyrrole derivatives.

Selective meta-arylation of O-β-naphthyl carbamate has been accomplished using Pd(OAc)2 as a catalyst precursor and K2S2O8 with AgOAc as the oxidant. A range of aryl boronic acids could be introduced in moderate to good yields. Mechanistic investigation shows that the carbamate substituent has a unique effect and the reaction undergoes an ortho-carbometallation/meta-direct arylation process.