Redox-neutral ortho-C–H amination of pinacol arylborates via palladium(ii)/norbornene catalysis for aniline synthesis† †Electronic supplementary information (ESI) available. See DOI: 10.1039/c9sc02759a

A palladium(ii)/norbornene cooperative catalysis enabled redox-neutral ortho-C–H amination of pinacol aryl- or heteroarylborates for the synthesis of structurally diverse anilines.


General information.
All reactions dealing with moisture-sensitive compounds were performed by standard Schlenk techniques in oven-dried reaction vessels under air atmosphere. Unless otherwise noted, all solvents were dried by JC Meyer Solvent Drying System. Most reagents were purchased from commercial sources and used without further purification, unless otherwise stated. Reactions were monitored by thin layer chromatography (TLC) carried out on 0.2 mm commercial silica gel plates, using UV light as the visualizing agent or basic solution of KMnO4 as a developing agent. 1 H NMR spectra were recorded on Bruker 400 MHz instrument and 13 C NMR spectra were recorded on Bruker 100 MHz instrument and were calibrated using residual undeuterated solvent as an internal reference (CDCl3 @ 7.26 ppm 1 H NMR, 77.16 ppm 13 C NMR). The following abbreviations were used to explain multiplicities: s = singlet, d = doublet, t = triplet, q = quartet, dd = doublet of doublets, dt = doublet of triplets, td = triplet of doublets, ddd = doublet of doublet of doublets, m = multiplet, br = broad. IR spectra were obtained on a Thermo Scientific Spectrum Nicolet iS10 spectrometer using thin films deposited on KBr plates (Thermo Fisher Scientific) and were reported in frequency of absorption (cm -1 ). Gas chromatography (GC) were recorded on Agilent 7890 instrument and the biphenyl as internal standard. High resolution mass spectra (HRMS) were recorded on DIONEX UltiMate 3000 & Bruker Compact TOF mass spectrometer.
To a 50 mL of oven-dried Schlenk tube equipped with a magnetic stir bar was charged with S1 (457 mg, 1.0 mmol, 1.0 equiv), Bis(pinacolato)diboron (280 mg, 1.1 mmol, 1.1 equiv), PdCl2(dppf) (36 mg, 0.05 mmol, 0.05 equiv), KOAc (290 mg, 3.0 mmol, 3.0 equiv) and DMSO (6 mL) under Ar atmosphere, then heated at 80 o C and stirred for 4 h. Then the reaction mixture was extracted with ethyl acetate (3 x 20 mL) and the combined organic layers were washed with brine (30 mL), dried over Na2SO4, filtered, and concentrated in vacuo. The residue was purified by column chromatography on silica gel (PE:EtOAc = 10:1) to yield the desired product 1ad (460 mg, 93% yield for two steps). and monitored by TLC. After completion of the reaction, the mixture was cooled to r.t., then filtered through a thin pad of celite, eluting with ethyl acetate (15 mL). The filtrate was sequentially washed with water, brine, dried over Na2SO4, filtered and concentrated in vacuo. The residue was purified by column chromatography on silica gel or by PTLC to yield the title product 3. Hz, 1H), 7.10 -7.07 (m, 1H), 3       Both the proton and carbon NMR match the literature reported data. 9

Deuterium labelling study with DMSO-d6.
To a 25 mL oven-dried Schlenk tube equipped with a magnetic stir bar was charged

Deuterium labelling study with Dioxane-d8.
To a 10 mL oven-dried Schlenk tube equipped with a magnetic stir bar was charged

Deuterium labelling study with 1-naphthylboronic ester-d7.
To a 25 mL oven-dried Schlenk tube equipped with a magnetic stir bar was charged The reaction was stirred at 70 o C. The reaction was monitored by TLC, after completion of the reaction, the mixture was cooled to r.t., then the mixture was filtered through a thin pad of celite eluting with ethyl acetate (15 mL), and the filtrate was sequentially washed with water, brine, dried over Na2SO4. After concentrated in vacuo, the residue was purified by column chromatography on silica gel to yield the desired product 3a-d.

Deuterium labelling study with D2O.
To a 25 mL oven-dried Schlenk tube equipped with a magnetic stir bar was charged