A radical decarboxylation/annulation of acrylamides with aliphatic acyl peroxides was developed, giving a series of linear alkylated oxindoles in moderate to good yields. The reaction used aliphatic acyl peroxides as the linear alkyl radical source and tolerated a broad scope of substrates under metal-free conditions, offering a simple and efficient approach toward alkylated oxindoles.

A metal-free 1,2-alkylarylation of allylic alcohols with aliphatic aldehydes through concomitant radical neophyl rearrangement was developed, providing 1,2-diphenyl-3-alkyl propanones in moderate to good yields. Moreover, when cyclopropanecarbaldehyde and aryl carbaldehydes were concerned, acylarylation was involved leading to 1,4-dicarbonyl compounds.

A direct arylation of inactivated benzene with acyl peroxides was developed, affording biaryls in good to excellent yields. This transformation underwent a radical pathway under metal-free, base-free and additive-free conditions with good functional group compatibility.

Alkyl-substituted isoquinoline-1,3(2H,4H)-diones were prepared by decarbonylative coupling of N-alkyl-N-methacryloylbenzamides and aliphatic aldehydes under metal-free conditions. The reaction undergoes subsequent decarbonylation, radical addition and cyclization processes with aliphatic aldehydes as the cheap and abundant alkyl radical source. This procedure offers a complementary approach to the convenient generation of alkyl-substituted isoquinoline-1,3(2H,4H)-diones.

A metal-free decarbonylative arylalkylation of N-(arylsulfonyl)acrylamides using aliphatic aldehydes as the alkyl radical source was developed, providing a series of α-aryl-β-alkylamides in moderate to good yields. In this reaction, concomitant alkylation, aryl migration and desulfonylation were involved.

Heterocyclic compounds are widely present in natural products, pharmaceuticals and bioactive molecules. Thus, organic and pharmaceutical chemists have been making extensive efforts to construct those heterocyclic frameworks through developing versatile and efficient synthetic strategies. The direct C–H functionalization via the radical pathway has emerged as a promising and dramatic approach towards heterocycles with high atom- and step-economy. Heterocyclic compounds such as coumarins, furans, benzofurans, xanthones, benzothiazoles, indoles, indolines, oxindoles, quinolines, isoquinolines, quinoxaline, and phenanthridines have been successfully synthesized by C–H functionalization through the radical pathway. In this review, recent advances on radical C–H functionalization to construct heterocyclic compounds are highlighted with discussions.

•A copper-catalyzed N-arylation/alkylation of sulfoximines was developed.•Acyl peroxides served as aryl/alkyl sources.•Mechanistic studies suggest radical pathway is involved in the procedure.A novel copper-catalyzed N-arylation/alkylation of sulfoximines with acyl peroxides as aryl/alkyl source was developed. This approach undergoes a radical pathway, representing an alternative complement to construct N-arylated/alkylated sulfoximines.

•An iron-catalyzed arylmethylation of activated alkenes was developed.•Di-tert-butyl peroxide (DTBP) served as the methyl radical source.•The cascade methyl radical addition, 1,4-aryl migration, and desulfonylation was involved.A novel iron-catalyzed arylmethylation of activated alkenes was developed using di-tert-butyl peroxide (DTBP) as the methyl radical source. This cascade process involved the sequential methyl radical addition, 1,4-aryl migration, and desulfonylation of sulfonyl acrylamides to afford a variety of α-aryl-β-methyl amides in good to moderate yields.

The oxidative difunctionalization of aryl alkynoates with alphatic aldehydes as a cheap and abundant alkyl radical source was developed, providing a variety of trisubstituted alkenes in moderate to good yields. In this reaction, radical decarbonylative alkylation of C-C triple bond, 1,4-aryl migration, and decarboxylation were involved under metal-free conditions.

The benzoyl peroxide (BPO) promoted carboannulation of ynones with alkanes is developed, affording a series of 2-alkyl-3-aryl indenones in moderate to good yields. The procedure involves direct functionalization of alkane C(sp3)–H and arene C(sp2)–H bonds under metal-free conditions, providing a favorable approach for indenone synthesis.

A copper-catalyzed oxidative C(sp3)–H/N–H coupling of sulfoximines with simple alkanes was developed. This protocol involved C(sp3)–N bond formation via a radical pathway and tolerated a series of functional groups, such as chloro, methyl and aryl, on the phenyl rings. Apart from sulfoximines, amides, saccharin and aniline also worked well to give the corresponding N-alkylated products.

The concise synthesis of 3-substituted or non-C3-substituted isoquinolines through Rh-catalyzed sequential oxidative C–H activation/annulation with geminal-substituted vinyl acetates was developed with good functional group tolerance. The protocol was successfully applied to the total synthesis of the natural product papaverine.

A protocol for the copper-catalyzed N-methylation of sulfoximines with di-tert-butyl peroxide (DTBP) was developed. This protocol has good functional group tolerance leading to N-methylated sulfoximines in moderate to good yields. Besides, N-ethylation of sulfoximines was achieved in the presence of bis(1,1-dimethylpropyl)peroxide as the ethylating agent under a standard procedure.

The Bu4NI-catalyzed α-oxyacylation of diarylethanones with acyl peroxides is developed. The reaction is conducted at room temperature without metal catalysts and tolerates a series of functional groups leading to α-oxyacylated diarylethanones in moderate to good yields.

A rhodium-catalyzed hydroarylation of alkynes with aryl tetrazoles through tetrazole-directed C–H activation was developed. This procedure has broad substrate scopes, and a variety of mono- and dialkenylated products were regioselectively obtained in moderate to excellent yields.

The tert-butyl hydroperoxide (TBHP) promoted sequential silylation and aromatisation of isonitriles was developed, where the silyl group was regioselectively installed at the 6-position of phenanthridines. This procedure tolerates a series of functional groups, such as fluoro, chloro, acetyl, methoxy carbonyl, cyano and trifluoromethyl. The addition of a silyl radical to the isonitrile followed by an intramolecular aromatic cyclization was involved in this transformation.

The tert-butyl hydroperoxide (TBHP)-promoted sequential carboxamidation and aromatisation of isonitriles with formamides was developed. This procedure tolerates a series of functional groups, such as methyl, fluoro, chloro, acetyl, methoxy carbonyl and cyano. This reaction involved the addition of formamide radicals to isonitriles and sequential C–C bond formation by intramolecular aromatic cyclisation, leading to phenanthridine 6-carboxamides in moderate to good yields.

A tert-butyl peroxybenzoate (TBPB)-promoted direct α-methylation of 1,3-dicarbonyl compounds has been developed, providing α-methyl derivatives in moderate to good yields. In this procedure, TBPB plays a dual role, serving as both the methyl source and radical initiator. This work represents a key complement to the traditional α-methylation of 1,3-dicarbonyl compounds using methyl iodide.

A metal-free decarbonylative arylalkylation of N-(arylsulfonyl)acrylamides using aliphatic aldehydes as the alkyl radical source was developed, providing a series of α-aryl-β-alkylamides in moderate to good yields. In this reaction, concomitant alkylation, aryl migration and desulfonylation were involved.

The dilauroyl peroxide (DLP)-promoted carboannulation of alkynoates with xanthates was developed, affording a series of 4-aryl-3-(β-carbonyl) coumarins in moderate to good yields. The difunctionalization of alkynoates was achieved via a radical addition/cyclization process under metal-free conditions.

Heterocyclic compounds are widely present in natural products, pharmaceuticals and bioactive molecules. Thus, organic and pharmaceutical chemists have been making extensive efforts to construct those heterocyclic frameworks through developing versatile and efficient synthetic strategies. The direct C–H functionalization via the radical pathway has emerged as a promising and dramatic approach towards heterocycles with high atom- and step-economy. Heterocyclic compounds such as coumarins, furans, benzofurans, xanthones, benzothiazoles, indoles, indolines, oxindoles, quinolines, isoquinolines, quinoxaline, and phenanthridines have been successfully synthesized by C–H functionalization through the radical pathway. In this review, recent advances on radical C–H functionalization to construct heterocyclic compounds are highlighted with discussions.

The tert-butyl hydroperoxide (TBHP)-promoted sequential carboxamidation and aromatisation of isonitriles with formamides was developed. This procedure tolerates a series of functional groups, such as methyl, fluoro, chloro, acetyl, methoxy carbonyl and cyano. This reaction involved the addition of formamide radicals to isonitriles and sequential C–C bond formation by intramolecular aromatic cyclisation, leading to phenanthridine 6-carboxamides in moderate to good yields.

A protocol for the copper-catalyzed N-methylation of sulfoximines with di-tert-butyl peroxide (DTBP) was developed. This protocol has good functional group tolerance leading to N-methylated sulfoximines in moderate to good yields. Besides, N-ethylation of sulfoximines was achieved in the presence of bis(1,1-dimethylpropyl)peroxide as the ethylating agent under a standard procedure.

The tert-butyl hydroperoxide (TBHP) promoted sequential silylation and aromatisation of isonitriles was developed, where the silyl group was regioselectively installed at the 6-position of phenanthridines. This procedure tolerates a series of functional groups, such as fluoro, chloro, acetyl, methoxy carbonyl, cyano and trifluoromethyl. The addition of a silyl radical to the isonitrile followed by an intramolecular aromatic cyclization was involved in this transformation.

A copper-catalyzed oxidative C(sp3)–H/N–H coupling of sulfoximines with simple alkanes was developed. This protocol involved C(sp3)–N bond formation via a radical pathway and tolerated a series of functional groups, such as chloro, methyl and aryl, on the phenyl rings. Apart from sulfoximines, amides, saccharin and aniline also worked well to give the corresponding N-alkylated products.

The concise synthesis of 3-substituted or non-C3-substituted isoquinolines through Rh-catalyzed sequential oxidative C–H activation/annulation with geminal-substituted vinyl acetates was developed with good functional group tolerance. The protocol was successfully applied to the total synthesis of the natural product papaverine.

A rhodium-catalyzed hydroarylation of alkynes with aryl tetrazoles through tetrazole-directed C–H activation was developed. This procedure has broad substrate scopes, and a variety of mono- and dialkenylated products were regioselectively obtained in moderate to excellent yields.

The Bu4NI-catalyzed α-oxyacylation of diarylethanones with acyl peroxides is developed. The reaction is conducted at room temperature without metal catalysts and tolerates a series of functional groups leading to α-oxyacylated diarylethanones in moderate to good yields.

Alkyl-substituted isoquinoline-1,3(2H,4H)-diones were prepared by decarbonylative coupling of N-alkyl-N-methacryloylbenzamides and aliphatic aldehydes under metal-free conditions. The reaction undergoes subsequent decarbonylation, radical addition and cyclization processes with aliphatic aldehydes as the cheap and abundant alkyl radical source. This procedure offers a complementary approach to the convenient generation of alkyl-substituted isoquinoline-1,3(2H,4H)-diones.