Redox‐Neutral Rhodium‐Catalyzed CH Functionalization of Arylamine N‐Oxides with Diazo Compounds: Primary C(sp³)H/C(sp²)H Activation and Oxygen‐Atom Transfer

Abstract

An unprecedented rhodium(III)-catalyzed regioselective redox-neutral annulation reaction of 1-naphthylamine N-oxides with diazo compounds was developed to afford various biologically important 1H-benzo[g]indolines. This coupling reaction proceeds under mild reaction conditions and does not require external oxidants. The only by-products are dinitrogen and water. More significantly, this reaction represents the first example of dual functiaonalization of unactivated a primary C(sp(3) )H bond and C(sp(2) )H bond with diazocarbonyl compounds. DFT calculations revealed that an intermediate iminium is most likely involved in the catalytic cycle. Moreover, a rhodium(III)-catalyzed coupling of readily available tertiary aniline N-oxides with α-diazomalonates was also developed under external oxidant-free conditions to access various aminomandelic acid derivatives by an O-atom-transfer reaction.

Diazo Compounds: Versatile Synthons for the Synthesis of Nitrogen Heterocycles via Transition Metal‐Catalyzed Cascade C–H Activation/Carbene Insertion/Annulation Reactions

“…[19] N,N-Dialkyl-1-arylamine N-oxides 26 containing primary C(sp 3 ) À H bonds or secondary C(sp 3 ) À Hb onds all worked well. [19] N,N-Dialkyl-1-arylamine N-oxides 26 containing primary C(sp 3 ) À H bonds or secondary C(sp 3 ) À Hb onds all worked well.…”

ChemInform Abstract: Redox‐Neutral Rhodium‐Catalyzed C—H Functionalization of Arylamine N‐Oxides with Diazo Compounds: Primary C(sp3)—H/C(sp2)—H Activation and Oxygen‐Atom Transfer.

“…(7)]. (8)]. Thec ompound 8a could be converted into 9a under the optimized rhodium(III)-catalyzed conditions,p resumably by ac ascade decarbonylation/hydroxy group elimination/nucleophilic addition, thus indicating the plausible intermediacyof8a in this reaction [Eq.…”

Direct Cyclization of Tertiary Aryl Amines with Iodonium Ylides

“…[11] Therefore,t he development of simple methods enabling the efficient construction of these Nheterocycles is an important topic of continuous scientific endeavor. [13] However,t his cyclization reaction was not applicable to phenylamine N-oxides.D espite these important achievements in the synthesis of indoline derivatives,t he development of alternative approaches that enable the direct cyclization of simple amines in the absence of precious transition metals without an additional superstoichiometric initiator/oxidant is an attractive yet substantially challenging goal. [13] However,t his cyclization reaction was not applicable to phenylamine N-oxides.D espite these important achievements in the synthesis of indoline derivatives,t he development of alternative approaches that enable the direct cyclization of simple amines in the absence of precious transition metals without an additional superstoichiometric initiator/oxidant is an attractive yet substantially challenging goal.…”

“…[13] However,t his cyclization reaction was not applicable to phenylamine N-oxides.D espite these important achievements in the synthesis of indoline derivatives,t he development of alternative approaches that enable the direct cyclization of simple amines in the absence of precious transition metals without an additional superstoichiometric initiator/oxidant is an attractive yet substantially challenging goal. Remarkably,i nc ontrast to the corresponding diazo compounds, [13] iodonium ylides showed exceptional reactivity,a st his cyclization does not require premodified amines and proceeds without the assistance of atransition-metal catalyst. Remarkably,i nc ontrast to the corresponding diazo compounds, [13] iodonium ylides showed exceptional reactivity,a st his cyclization does not require premodified amines and proceeds without the assistance of atransition-metal catalyst.…”