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-lodophenyl)-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{C6H4NHC(O)NHTo-2}IL2] (To = C6H4Me-4; L-2 = tbubpy (4,4'-di-tert-butyl-2,2'-bipyridine) (2a), tmeda (N,N,N ',N '-tetramethylethylenediamine) (2b); L = PPh3 (2c)). Reaction of 2b with Tl(TfO) TfO = triflate, CF3SO3) results in the formation of cyclopalladated [Pd{kappa C-2,O- C6H4NHC(O)NHTo-2}(tmeda)]OTf (3b). The latter reacts with PPh3 to yield [Pd{C6H4NHC-(O)NHTo-2}(tmeda)(PPh3)]OTf (4b). Treatment of 2b with CO gives the corresponding acyl derivative [Pd{C(O)C6H4NHC(O)NHTo-2}I(tmeda)] (5b). If Tl(TfO) is added after the bubbling of CO, the C,N coupling product 3-p-tolyl-1H-quinazoline-2,4-dione (6) is formed. Complex 5b reacts with XyNC (Xy = 2,6-dimethylphenyl) to yield trans- [Pd{C(O)C6H4NHC-(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)C6H4NHC(O)NHTo-2}I(CNR)2] (R = Xy (8x), Bu-t (8t)). The complex 8x gives the C,N coupling product 4-(xylylimino)-3-p-tolyl-3,4-dihydro-1H-quinazolin-2-one (9) after treatment with TlOTf 8x also reacts with bases (K2CO3 and Tl2CO3) to yield the iminoacyl amido carbene C,N,C pincer palladium complex [Pd{kappa C-3,N,C-C(=NXy)C6H4NC(O)NToC(NHXy)-2}(CNXy)] (10); this complex is an active precatalyst in Heck and Suzuki reactions. The reaction of 2b with R'C equivalent to CR and TIOTf gives [Pd{kappa C-2,N-CR'=CRC6H4NHC(O)NHTo-2}(tmeda)]OTf (R' = R = Et (11be), CO2Me (11bm), Ph (11bp); R' = Ph, R = CO2Me (11bq)). These complexes decompose in solution, and in the case of 11bp, 2,3-diphenylindole-l-carboxylic acid p-tolylamide (12p) was isolated. 11bq reacts with PPh3 to give 3-phenyl-1H-indole-2carboxylic 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-OEt2, 11bq, and 14po have been determined.