Synthesis and Reactivity of Ortho-Palladated Arylureas. Synthesis and Catalytic Activity of a C,N,C Pincer Complex. Stoichiometric Syntheses of Some N-Heterocycles

1-(2-Iodophenyl)-3- p -tolylurea ( 1 ) reacts with Pd(dba) 2 ([Pd 2 (dba) 3 ]·dba; dba = dibenzylideneacetone) in the presence of the appropriate ligands to give the ortho-palladated arylureas [Pd{C 6 H 4 NHC(O)NHTo-2}IL 2 ] (To = C 6 H 4 Me-4; L 2 = tbubpy (4,4‘-di- tert -butyl-2,2‘-bipyridine) ( 2a ), tmeda ( N, N, N ‘, N ‘-tetramethylethylenediamine) ( 2b ); L = PPh 3 ( 2c )). Reaction of 2b with Tl(TfO) (TfO = triflate, CF 3 SO 3 ) results in the formation of cyclopalladated [Pd{κ 2 C, O- C 6 H 4 NHC(O)NHTo-2}(tmeda)]OTf ( 3b ). The latter reacts with PPh 3 to yield [Pd{C 6 H 4 NHC(O)NHTo-2}(tmeda)(PPh 3 )]OTf ( 4b ). Treatment of 2b with CO gives the corresponding acyl derivative [Pd{C(O)C 6 H 4 NHC(O)NHTo-2}I(tmeda)] ( 5b ). If Tl(TfO) is added after the bubbling of CO, the C,N coupling product 3- p -tolyl-1 H -quinazoline-2,4-dione ( 6 ) is formed. Complex 5b reacts with XyNC (Xy = 2,6-dimethylphenyl) to yield trans- [Pd{C(O)C 6 H 4 NHC(O)NHTo-2}I(CNXy) 2 ] ( 7 ). Both 5b and 7 decompose in solution to give 6 . Complex 2b reacts with isocyanides to give the iminoacyl derivatives trans- [Pd{C( NR)C 6 H 4 NHC(O)NHTo-2}I(CNR) 2 ] (R = Xy ( 8x ), t Bu ( 8t )). The complex 8x gives the C,N coupling product 4-(xylylimino)-3- p -tolyl-3,4-dihydro-1 H -quinazolin-2-one ( 9 ) after treatment with TlOTf. 8x also reacts with bases (K 2 CO 3 and Tl 2 CO 3 ) to yield the iminoacyl amido carbene C,N,C pincer palladium complex [Pd{κ 3 C, N,C - C( NXy)C 6 H 4 NC(O)NToC(NHXy)-2}(CNXy)] ( 10 ); this complex is an active precatalyst in Heck and Suzuki reactions. The reaction of 2b with R‘C⋮CR‘ ‘ and TlOTf gives [Pd{κ 2 C, N -CR‘ CR‘ ‘C 6 H 4 NHC(O)NHTo-2}(tmeda)]OTf (R‘ = R‘ ‘ = Et ( 11be ), CO 2 Me ( 11bm ), Ph ( 11bp ); R‘ = Ph, R‘ ‘ = CO 2 Me ( 11bq )). These complexes decompose in solution, and in the case of 11bp, 2,3-diphenylindole-1-carboxylic acid p -tolylamide ( 12p ) was isolated. 11bq reacts with PPh 3 to give 3-phenyl-1 H -indole-2-carboxylic acid methyl ester ( 13q ). 11bp and 11bq decompose in the presence of CO to yield 3,4-diphenyl-2-quinolone ( 14po ) and 2-oxo-4-phenyl-1,2-dihydroquinoline-3-carboxylic acid methyl ester ( 14qo ), respectively. Similarly, when 11bq is reacted with XyNC, the C,N coupling compound 2-xylyl-4-phenyl-1,2-dihydroquinoline-3-carboxylic acid methyl ester ( 14qnx ) is formed. The crystal and molecular structures of 3b, 10 ·0.5CDCl 3, 11bp ·OEt 2, 11bq, and 14po have been determined.