Ruthenium-Catalyzed ortho/meta-Selective Dual C–H Bonds Functionalizations of Arenes

Abstract

The first example of transition-metal-catalyzed ortho/meta-selective dual C-H functionalizations of arenes in one reaction is described. In this transformation, ortho-C-H chlorination and meta-C-H sulfonation of 2-phenoxypyri(mi)dines were achieved simultaneously under catalysis by [Ru(p-cymene)Cl]. The other reactant, namely, an arylsulfonyl chloride, played the role of both a sulfonation and chlorination reagent. More importantly, the arylsulfonyl chloride was also an oxidant in the process. Mechanistic studies indicated that six-membered ruthenacycles were the key intermediate in the reaction.

Ruthenium‐Catalyzed meta‐CAr–H Bond Difluoroalkylation of 2‐Phenoxypyridines

“…However, these methods have been mainly limited to ortho ‐C Ar –H bond functionalizations. Recently, with the help of the strong ortho/para ‐directing character of Ru–C Ar σ‐bonds, we have achieved meta ‐C–H alkylation and sulfonylation of 2‐phenoxypyridine …”

Recent Advancements in Transition‐Metal‐Catalyzed One‐Pot Twofold Unsymmetrical Difunctionalization of Arenes

“…In 2017, Li and co‐workers described ruthenium(II)‐catalyzed removable 2‐phenoxypyridine assisted twofold meta ‐C−H and ortho ‐C−H functionalizations of arenes via dual unsymmetrical C‐heteroatom bond formation in one‐pot (Scheme ) . The highly position selective meta ‐C−H sulfonylation and concomitant ortho ‐C−H chlorination were accomplished through ortho / para ‐directing effects of Ru‐C Ar σ‐bonds in presence of [Ru( p ‐cymene)Cl 2 ] 2 as a catalyst in xylene at 120 °C, where arylsulfonyl chloride served a dual role of both sulfonylating and chlorinating agent.…”

“…In 2017, Li and co-workers described ruthenium(II)-catalyzed removable2 -phenoxypyridine assisted twofold meta-CÀHa nd ortho-CÀHf unctionalizations of arenes via dual unsymmetrical C-heteroatom bond formation in one-pot (Scheme 27). [29] The highly position selective meta-CÀHs ulfonylation and concomitant ortho-CÀHc hlorination were accomplished through ortho/ Scheme24. One-pot sequential twofold unsymmetrical meta-and ortho-CÀ Hf unctionalizations.…”

Ruthenium‐Mediated Distal C−H Activation

“…Li and co‐workers outline sequential meta ‐alkylation and meta ‐sulfonation reactions on an atypical 2‐phenoxypyridine template, which also serves as a removable handle, to yield meta ‐alkylated/ meta ‐sulfonated phenols. In this case, a radical mechanism is described for both regioselective functionalization reactions (Scheme ) …”

“…In this case, ar adical mechanism is described for both regioselective functionalization reactions (Scheme 10). [26,27] In an ensuing report, Zhang and co-workers report an improvement of their earlier meta-nitration strategy.B etter yields are secured by manipulating the directingm oiety to an oxime (a removable auxiliary) under milder reaction conditions. AgNO 3 is used as the nitratinga gent insteado fC u(NO 3 ) 2 ·3H 2 O in combination with PhI(TFA) 2 ([bis(trifluoroacetoxy)iodo]benzene) to generate the NO 2 radical, and O 2 acts as the oxidant.…”