Synthesis and Reactivity of Ortho-Palladated Arylcarbodiimides and Aryl Isothiocyanates. Formation of C-Palladated Quinazolines. Synthesis of 2-Aminoquinolines

The iminophosphoranes Ph 3 P NC 6 H 3 X-2-R-4 (X = I, R = H ( 1a ); X = Br, R = NO 2 ( 1b ); X = Br, R = Me ( 1c )) react with p -tolyl isocyanate and 1a reacts with CS 2 to give the carbodiimides ToN C NC 6 H 3 X-2-R-4 (To = C 6 H 4 Me-4; X = I, R = H ( 2a ); X = Br, R = NO 2 ( 2b ); X = Br, R = Me ( 2c )) and the isothiocyanate S C NC 6 H 4 I-2 ( 3 ), respectively. The compounds 2 and 3 react with Pd(dba) 2 ([Pd 2 (dba) 3 ]·dba, dba = dibenzylideneacetone) in the presence of the appropriate ligands to give the ortho-palladated arylcarbodiimides [Pd(C 6 H 3 N C NTo-2-R-5)XL 2 ] (L = PPh 3, X = I, R = H ( 4a ); L = PPh 3, X = Br, R = NO 2 ( 4b ), Me ( 4c ); L 2 = bpy (2,2‘-bipyridine), X = I, R = H ( 5a )) and trans -[Pd(C 6 H 4 N C S-2)I(PPh 3 ) 2 ] ( 6 ), respectively. Complex 4a reacts with pyridine (py) and Tl(TfO) (TfO = triflate, CF 3 SO 3 ) and 5a reacts with 4- tert -butylpyridine ( t Bupy) and Tl(TfO) to give the complexes trans -[Pd(C 6 H 4 N C NTo-2)(py)(PPh 3 ) 2 ]TfO ( 7a ) and [Pd(C 6 H 4 N C NTo-2)( t Bupy)(bpy)]TfO ( 8a ), respectively. Complex 4a reacts with XyNC (Xy = 2,6-dimethylphenyl) to give the palladated quinazoline trans -[Pd(ToNqXy)I(CNXy) 2 ] (ToNqXy = 3-(2,6-dimethylphenyl)-2-[(4-methylphenyl)imino]-2,3-dihydroquinazolin-4-yl ( 9a )) and with t BuNC to give [Pd(ToNq t Bu)I(CN t Bu)(PPh 3 )] (ToNq t Bu = 3- tert -butyl-2-[(4-methylphenyl)imino]-2,3-dihydroquinazolin-4-yl ( 10a ‘)). Reaction of 10a ‘ with Tl(TfO) and PPh 3 results in the formation of trans -[Pd(ToNHq)(CN t Bu)(PPh 3 ) 2 ]TfO ( 11; ToNHq = 2-[(4-methylphenyl)amino]quinazolin-4-yl). The reaction of R‘C⋮CR‘ with 4a, 5a, or 4c gives 2-[(4-methylphenyl)amino]-3,4-R‘ 2 -6-R-quinoline (R‘ = CO 2 Me, R = H ( 12a), Me ( 12c ); R‘ = Ph, R = H ( 12a ‘)). Some of these reactions require the presence of Tl(TfO). The crystal and molecular structures of 6, 8a ·CDCl 3, 9a ·0.5OEt 2, 11, 12a, and 12a ‘ have been determined.