Tandem cyclization/arylation of diaryliodoniums via in situ constructed benzoxazole as a directing group for atom-economical transformation

Abstract

Linear diaryliodoniums often undergo only single arylation and leave equivalent aryliodide as waste. Herein, we demonstrate that linear unsymmetrical diaryliodoniums could be tuned by dual nickel/palladium metal system to accomplish...

Copper‐Catalyzed One‐Pot Arylation and Cyclization of Diaryliodonium Salts Derived fromo‐Iodoanilines for Indolo[2,3‐b]indoles Syntheses

“…Many methods have already been reported for the preparation of oxazoles from diaryliodonium salts [21][22][23] because of their applicability in pharmaceutical and material industry. Zhu and co-workers synthesized axially chiral oxazoles by a ring opening and intramolecular cyclization of cyclic diaryliodonium salts.…”

“…[22] Very recently, Wen's group reported a nickel catalyzed intramolecular cyclization of (2-benzamidophenyl)-(aryl)iodonium triflates to access 2-arylbenzoxazoles. [23] Despite extensive previous studies, we further investigated the transformation to expand application of the iodonium salts derived from o-iodoanilines. The reaction was conducted using 6 a with triflate (OTf) counterion in order to examine the influence of counterion.…”

“…utilized cyclic diaryliodonium salts to achieve regioselective alkynylation followed by intramolecular cyclization with Cu/Pd dual‐metal catalytic system [22] . Very recently, Wen′s group reported a nickel catalyzed intramolecular cyclization of (2‐benzamidophenyl)‐(aryl)iodonium triflates to access 2‐arylbenzoxazoles [23] . Despite extensive previous studies, we further investigated the transformation to expand application of the iodonium salts derived from o ‐iodoanilines.…”

Transition Metal‐FreeO‐Arylation ofN‐Alkoxybenzamides Enabled by Aryl(trimethoxyphenyl)iodonium Salts

“…The unique reactivity of diaryliodonium salts allows the arylation of diverse carbon and heteroatom nucleophiles to proceed smoothly under mild conditions in the presence or absence of transition metals. For example, the intramolecular cyclization of amide groups tethered to diaryliodonium salts in the presence of Ni(OTf) 2 or CuI afforded the related benzoxazole derivatives via Ar–O bond formation [19a,b] . In addition, Cu(OTf) 2 catalyzed the O ‐arylation of the pyridyl amidate functionality in the presence of Ar 2 IPF 6 for a few selected substrates (Scheme 1c) [19c] .…”

Benzoxazole or Benzothiazole as an Innate Directing Group for Palladium- and Ruthenium-Catalyzed Complementary C–H Arylation: Functionalization of Biorelevant Heterocyclic Scaffolds

“…mechanistic cycle involving a sequence of cyclopalladation followed by oxidative addition of 2 could be anticipated. 28,30,31 Since the Ru(II) center is fairly electrophilic, 36,62 it is reasonable that catalytic cycle 2 (Scheme 6) will start with ortho C-H activation of 1 or 4 and would provide a complementary catalytic cycle. At first, dimeric [RuCl 2 (p-cym)] 2 (I) breaks up in the presence of AgBF 4 to generate catalytically active cationic ruthenium species II, which undergoes coordination with the nitrogen atom of the benzoxazole/benzothiazole unit of 1 or 4 to provide species F. In a subsequent step, species F follows a ligand-assisted CMD process 56 for ortho C-H activation via G and gives the ruthenacycle H. Oxidative addition of H to 2 generates Ru(IV) species I, which, on final reductive elimination, assisted by Ag + ion, affords the desired ortho C-H arylated product 3 or 5 along with the regeneration of Ru(II) species II available for the next catalytic run.…”