Catalytic Coupling of Aryl Sulfonates with sp2-Hybridized Nitrogen Nucleophiles: Palladium- and Nickel-catalyzed Synthesis of N-Aryl Sulfoximines

Abstract

Several sulfoximines have been arylated in good to high yield by palladium catalysis using aryl nonaflates and aryl triflates. Moreover, the successful synthesis of N-aryl sulfoximines from aryl tosylates is described using a Ni(COD) 2 /BINAP catalyst.Palladium-catalyzed processes which employ aryl or vinyl sulfonates 1 are becoming increasingly attractive, because they are easily accessible from the corresponding phenols and ketones, respectively, thus allowing an entirely different class of substrates -other than aryl or vinyl halides -to be utilized as starting materials. For example, aryl triflates have been widely used in Heck 2 and SuzukiMiyaura 3 type couplings and more recently, they have also been employed in the palladium-catalyzed synthesis of aryl amines. 4 An important improvement for the latter transformation was achieved when NaOt-Bu -which was responsible for the formation of large amounts of hydrolytic byproducts of the aryl triflate 5 -was replaced by cesium carbonate. This mild base led to both an increased functional group tolerance and a dramatically decreased rate of the hydrolysis of the triflate precursors. 6 Compared to aryl triflates, the corresponding nonaflates are even more attractive substrates because they display a higher reactivity and a more pronounced stability towards hydrolysis. 7 Despite of all of these positive characteristics of aryl sulfonates, palladium-catalyzed aminations of aryl sulfonates with sp 2 -hybridized nitrogen nucleophiles other than benzophenone imine are still rare. 8Recently, we established a novel method for the catalytic N-arylation of sulfoximines with aryl bromides and aryl iodides which has already been applied by Harmata and Parvi in the synthesis of benzothiazines. 9,10 In this protocol Pd(OAc) 2 /BINAP serves as catalyst and cesium carbonate acts as base allowing for mild reaction conditions and broad functional group tolerance (Scheme 1).Herein, we report on the extension of this sulfoximine N-arylation method first, to palladium-catalyzed reactions of sulfoximines with aryl triflates and aryl nonaflates and second, to nickel-catalyzed couplings of sulfoximines and aryl tosylates. (2) under essentially identical reaction conditions as for couplings of aryl bromides, led to the formation of the corresponding products in good to high yields (Table, Entries 1-5). Interestingly, the substrate which is most susceptible toward hydrolysis -4-nitrophenyl triflate -gave the highest yield of coupling product 7 at 86% indicating that triflate hydrolysis is no serious side reaction. Aryl nonaflates 7,11 reacted also smoothly in the presence of a catalytic amount of Pd(OAc) 2 /BINAP affording the corresponding N-aryl sulfoximines in good to high yields (Table, Entries 6-8). For example, N-(4-tert-butylphenyl) S-methyl-S-(p-tolyl) sulfoximine was obtained with a yield of 76%, which is remarkable taken into account that this compound is formed in only 67% yield from the corresponding aryl bromide. As in reactions with aryl triflates electron-deficient aryl nonaf...

Room-temperature nickel-catalyzed amination of heteroaryl/aryl chlorides with Ni(II)–(σ-Aryl) complex as precatalyst

“…Bolm provided the example for the amination of aryl tosylates with sulfoximines by employing BINAP as ligand for Ni(0) [5]. Fort developed the Ni(II)eNaHebipyridine [6e9] and Ni(II)eNaHeNHC [10] systems as efficient catalysts for the couplings of aryl and heteroaryl chlorides with various nitrogencontaining substrates.…”

Ni‐Catalyzed Amination Reactions: An Overview

“…In 2000, Bolm and coworkers, while studying the palladium‐catalyzed arylation of sulfoximines with aryl triflates and nonaflates, found that a Ni(cod) 2 /BINAP catalyst mediated the coupling of aryl tosylates with sulfoximine (two examples only), whereas palladium did not (Scheme ) 61…”

Facile and Efficient Amination of Organic Halides Catalyzed by Copper Sulfate in PEG1000‐DIL/Methylcyclohexane Temperature‐Dependent Biphasic System

“…[5][6][7][8][9][10][11][12] However, the cost of reagents, removal of trace palladium from late stage synthetic intermediate, and difficulties in coupling of electron-rich or ortho-substituted aryl halides are the major drawbacks of this method. In addition to palladium catalysts, rhodium, [13][14][15][16] and nickel [17][18][19][20] transition metal catalysts have been developed for N-arylation of aryl halides with amines, however, these methods have drawbacks in terms of atom economy, since they generate large amounts of solid waste and also require a stoichiometric amount of base. Copper mediated N-arylation is another choice of reaction for the production of these compounds due to cheap price and environmental friendly nature.…”