Xuan-Hui Ouyang

Metal-free oxidative tandem coupling of activated alkenes with carbonyl C(sp2)–H bonds and aryl C(sp2)–H bonds using TBHP

A metal-free oxidative tandem coupling of activated alkenes with carbonyl C(sp2)–H bonds and aryl C(sp2)–H bonds using TBHP is established for the synthesis of 3-(2-oxoethyl)indolin-2-ones. This method allows 1,2-difunctionalization of the C–C double bond in N-arylacrylamides by simultaneous formation of two C(sp2)–C(sp3) bonds.

Rhodium(III)‐Catalyzed [3+2]/[5+2] Annulation of 4‐Aryl 1,2,3‐Triazoles with Internal Alkynes through Dual C(sp2)H Functionalization

A rhodium(III)-catalyzed [3+2]/[5+2] annulation of 4-aryl 1-tosyl-1,2,3-triazoles with internal alkynes is presented. This transformation provides straightforward access to indeno[1,7-cd]azepine architectures through a sequence involving the formation of a rhodium(III) azavinyl carbene, dual C(sp(2))-H functionalization, and [3+2]/[5+2] annulation.

Metal-Free Radical [2+2+1] Carbocyclization of Benzene-Linked 1,n-Enynes: Dual C(sp3)-H Functionalization Adjacent to a Heteroatom

A new metal-free oxidative radical [2+2+1] carbocyclization of benzene-linked 1,n-enynes with two C(sp(3))-H bonds adjacent to the same heteroatom is described. This method achieves two C(sp(3))-H oxidative functionalizations and an annulation, thus providing efficient and general access to a variety of fused five-membered carbocyclic hydrocarbons.

Metal-Free Oxidative Ipso-Carboacylation of Alkynes: Synthesis of 3-Acylspiro[4,5]trienones from N-Arylpropiolamides and Aldehydes

A general and metal-free radical route to synthesis of 3-acylspiro[4,5]trienones is established that utilizes TBHP (tert-butyl hydrogenperoxide) as an oxidation and a reaction partner to trigger the oxidative ipso-carboacylation of N-arylpropiolamides with aldehydes. This method offers a new difunctionalization of alkynes through oxidative cross coupling of the aldehyde C(sp(2))-H bond with an ipso-aromatic carbon.

Copper-catalyzed oxidative ipso-carboalkylation of activated alkynes with ethers leading to 3-etherified azaspiro[4.5]trienones

Cu-catalyzed synthesis of 3-etherified azaspiro[4.5]trienones from N-arylpropiolamides and ethers is presented using TBHP oxidant. This is achieved through C(sp3)–H functionalization, ipso-carbocyclization and dearomatization, and this method represents a new example of alkyne oxidative 1,2-difunctionalization with an ipso-aromatic carbon and a C(sp3)–H bond by simultaneously forming two new carbon–carbon bonds.

Copper-Catalyzed Radical [2 + 2 + 1] Annulation of Benzene-Linked 1,n-Enynes with Azide: Fused Pyrroline Compounds

A novel selective copper-catalyzed radical [2 + 2 + 1] annulation of benzene-linked 1,n-enynes with azido-benziodoxolone to access fused pyrroline compounds, including 3H-pyrrolo[3,4-c]quinolin-4(3aH)-ones, chromeno[3,4-c]pyrrol-4(9bH)-one, and indeno[1,2-c]pyrroline, has been developed, which proceeds via the addition of the azide radical to the alkene, annualtion, and azidation cascade.

Silver-Mediated Intermolecular 1,2-Alkylarylation of Styrenes with α-Carbonyl Alkyl Bromides and Indoles.

A new iron-facilitated silver-mediated radical 1,2-alkylarylation of styrenes with α-carbonyl alkyl bromides and indoles is described, and two new C-C bonds were generated in a single step through a sequence of intermolecular C(sp(3)-Br functionalization and C(sp(2))-H functionalization across the alkenes. This method provides an efficient access to alkylated indoles with broad substrate scope and excellent selectivity.

Alkylation/1,2-aryl migration of α-aryl allylic alcohols with α-carbonyl alkyl bromides using visible-light photoredox catalysis

A novel visible-light-induced alkene difunctionalization strategy is described for the synthesis of 1,5-dicarbonyl compounds from two reaction partners, α-aryl allylic alcohols and α-carbonyl alkyl bromides. This method is successful by sequential alkylation of an alkene C–C double bond and intramolecular 1,2-aryl migration, and shows a broad substrate scope, excellent functional group tolerance and good selectivity.

Iron-Catalyzed Intermolecular 1,2-Difunctionalization of Styrenes and Conjugated Alkenes with Silanes and Nucleophiles

The first iron-catalyzed 1,2-difunctionalization of styrenes and conjugated alkenes with silanes and either N or C, using an oxidative radical strategy, is described. Employing FeCl2 and di-tert-butyl peroxide allows divergent alkene 1,2-difunctionalizations, including 1,2-aminosilylation, 1,2-arylsilylation, and 1,2-alkylsilylation, which rely on a wide range of nucleophiles, namely, amines, amides, indoles, pyrroles, and 1,3-dicarbonyls, thus providing a powerful platform for producing diverse silicon-containing alkanes.

Metal-free carbonyl C(sp2)–H oxidative alkynylation of aldehydes using hypervalent iodine reagents leading to ynones

A new metal-free tert-butyl hydroperoxide (TBHP)-mediated carbonyl C(sp(2))-H oxidative alkynylation of aldehydes with ethynyl benziodoxolones (EBX) for the synthesis of ynones is described. This method is based on a carbonyl C(sp(2))-H oxidative radical coupling process according to mechanistic studies, and provides a general route to the assembly of diverse ynones with a broad substrate scope and excellent functional-group compatibility.