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 ([Pd2(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; L2 = 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{κ2C,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), tBu (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{κ3C,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⋮CR‘ ‘ and TlOTf gives [Pd{κ2C,N-CR‘CR‘ ‘C6H4NHC(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-1-carboxylic acid
p-tolylamide (12p) was isolated. 11bq reacts with PPh3 to give 3-phenyl-1H-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, 10·0.5CDCl3, 11bp·OEt2,
11bq, and 14po have been determined.

1-(2-碘苯基)-3-对甲苯基脲(1)与Pd(dba)₂（[Pd₂(dba)₃]·dba；dba=二亚苄基丙酮（dibenzylideneacetone））在合适配体存在下反应，得到邻位环钯化芳基脲类配合物[Pd{C₆H₄NHC(O)NHTo-2}IL₂]（其中To=C₆H₄Me-4即对甲苯基；L₂=tbubpy（4,4'-二叔丁基-2,2'-联吡啶）(2a)、tmeda（N,N,N',N'-四甲基乙二胺）(2b)；L=PPh₃（三苯基膦）(2c)）。2b与Tl(TfO)（TfO=三氟甲磺酰氧基（triflate, CF₃SO₃））反应，生成环钯化配合物[Pd{κ²C,O-C₆H₄NHC(O)NHTo-2}(tmeda)]OTf (3b)。该配合物与三苯基膦反应，得到[Pd{C₆H₄NHC(O)NHTo-2}(tmeda)(PPh₃)]OTf (4b)。用CO处理2b，可得到相应的酰基衍生物[Pd{C(O)C₆H₄NHC(O)NHTo-2}I(tmeda)] (5b)。若在通入CO后加入Tl(TfO)，则生成C,N偶联产物3-对甲苯基-1H-喹唑啉-2,4-二酮(6)。配合物5b与XyNC（Xy即2,6-二甲基苯基，二甲苯基）反应，得到反式-[Pd{C(O)C₆H₄NHC(O)NHTo-2}I(CNXy)₂] (7)。5b与7在溶液中均会分解，得到产物6。配合物2b与异氰化物反应，生成亚氨酰基衍生物反式-[Pd{C(=NR)C₆H₄NHC(O)NHTo-2}I(CNR)₂]（R=Xy(8x)、tBu（叔丁基）(8t)）。配合物8x经TlOTf处理后，得到C,N偶联产物4-(二甲苯基亚氨基)-3-对甲苯基-3,4-二氢-1H-喹唑啉-2-酮(9)。8x还可与碱（K₂CO₃碳酸钾和Tl₂CO₃碳酸亚铊）反应，得到亚氨酰基酰胺卡宾C,N,C钳形钯配合物[Pd{κ³C,N,C-C(=NXy)C₆H₄NC(O)NToC(NHXy)-2}(CNXy)] (10)；该配合物是Heck反应与Suzuki反应的活性预催化剂。配合物2b与R'C≡CR''以及TlOTf反应，生成[Pd{κ²C,N-CR'=CR''C₆H₄NHC(O)NHTo-2}(tmeda)]OTf（其中R'=R''=Et（乙基）(11be)、CO₂Me（甲氧羰基）(11bm)、Ph（苯基）(11bp)；R'=Ph，R''=CO₂Me(11bq)）。上述配合物在溶液中均会发生分解，对于11bp，可分离得到2,3-二苯基吲哚-1-羧酸对甲苯基酰胺(12p)。11bq与三苯基膦反应，得到3-苯基-1H-吲哚-2-羧酸甲酯(13q)。11bp和11bq在CO存在下分解，分别得到3,4-二苯基-2-喹啉酮(14po)和2-氧代-4-苯基-1,2-二氢喹啉-3-羧酸甲酯(14qo)。类似地，当11bq与XyNC反应时，生成C,N偶联产物2-二甲苯基-4-苯基-1,2-二氢喹啉-3-羧酸甲酯(14qnx)。已测定配合物3b、10·0.5CDCl₃、11bp·OEt₂、11bq以及14po的晶体与分子结构。