Conversion of iminoacyl quinolinylpalladium (II) complexes into novel oxo‐pyrrolo[3,4‐ b ] quinolines via depalladation reactions

Oxidative addition reactions of quinolines 1a , b with Pd(dba) 2 in the presence of PPh 3 (1:2) in acetone gave dinuclear palladium complexes [Pd( C ,N‐2‐C 9 H 4 N‐CHO‐3‐R‐6)Cl(PPh 3 )] 2 [(R = H ( 2a ), R = OMe ( 2b ), which were reacted with isocyanide XyNC (Xy = 2,6‐Me 2 C 6 H 3 ) to give novel iminoacyl quinolinylpalladium complexes 3a , b in good yields (81 and 77%). Cyclopalladated complexes 3a , b were also obtained in low yields (39 and 33.5%) via one‐pot reaction of 1a , b with isonitrile XyNC:Pd(dba) 2 (4:1). The reaction of 3a , b with Tl(TfO) (TfO = triflate, CF 3 SO 3 ) in the presence of H 2 O or EtOH causes depalladation reactions of complexes to provide the corresponding organic compounds 4a , b , 5a , b and 6a , b in yields of 41, 27 and 18 − 19%, respectively. The products were characterized by satisfactory elemental analyses and spectral studies (IR, 1 H, 13 C and 31 P NMR). The crystal structures 2a , 3a and 3b were determined by X‐ray diffraction studies. Copyright © 2008 John Wiley & Sons, Ltd.