ADC-Based Palladium Catalysts for Aqueous Suzuki–Miyaura Cross-Coupling Exhibit Greater Activity than the Most Advantageous Catalytic Systems

The reaction between the equimolar amounts of cis-[PdCl2(CNR1)2] (R1 = cyclohexyl (Cy) (1), tBu (2)) and the carbohydrazides R2CONHNH2 (R2 = Ph (5), 4-ClC6H4 (6), 3-NO2C6H4 (7), 4-NO2C6H4 (8), 4-CH3C6H4 (9), 3,4-(MeO)2C6H3 (10), naphth-1-yl (11), fur-2-yl (12), 4-NO2C6H4CH2 (13), Cy (14), 1-(4-fluorophenyl)-5-oxopyrrolidin-3-yl (15), (pyrrolidin-1-yl)C(O) (16)) proceeds in refluxing CHCl3 for ca. 4 h. A subsequent workup provided the aminocarbene species cis-[PdCl2{C(NHNHC(O)R2)═N(H)R1}(CNR1)] (18–33) in good to excellent (80–95%) isolated yields. The coupling of equimolar amounts of cis-[PdCl2(CNR1)2] (R1 = Cy (1), tBu (2), 2,6-Me2C6H3 (Xyl) (3), 2-Cl-6-MeC6H3 (4)) and PhSO2NHNH2 (17) occurs similarly and affords the aminocarbenes cis-[PdCl2{C(NHNHS(O)2Ph)═N(H)R1}(CNR1)] (34–37; 60–90%). Complexes 18–37 were characterized by elemental analyses (C, H, N), ESI+-MS, IR, and 1D (1H, 13C{1H}) and 2D (1H,1H-COSY, 1H,13C-HMQC/1H,13C-HSQC, 1H,13C-HMBC) NMR spectroscopy, as well as by X-ray diffraction for three ...