Copper-catalyzed radical cascade oxyalkylation of olefinic amides with simple alkanes: highly efficient access to benzoxazines

Synthesis of 2,4-Dicyanoalkylated Benzoxazines through the Radical-Mediated Cascade Cyclization of Isocyanides with AIBN under Metal- and Additive-Free Conditions

A general and novel method for the radical cascade cyclization of aryl isocyanides with AIBN has been described. This strategy provides straightforward access to various 2,4-dicyanoalkylated benzoxazines in moderate to good yields under metal- and additive-free conditions. The reaction can apply to a gram scale and tolerate diverse functional groups. 2,4-Dicyanoalkylated benzoxazine derivatives feature a large Stokes shift and intramolecular charge transfer properties.

Electrochemical oxidative cyclization of N-allylamides for the synthesis of CF3-containing benzoxazines and oxazolines

The introduction of trifluoromethyl (-CF3) groups into compounds is a common synthetic strategy in organic chemistry. Commonly used methods for introducing trifluoromethyl groups are limited by harsh reaction conditions, low regioselectivity, or the need for excess reagents. In this study, a facile electrochemical oxidative and radical cascade cyclization of N-(2-vinylphenyl)amides for the synthesis of CF3-containing benzoxazines and oxazolines was obtained. This sustainable protocol features inexpensive and durable electrodes, a wide range of substrates, diverse functional group compatibility under transition-metal-free, external-oxidant-free, and additive-free conditions, and can be applied in an open environment.

Electrochemical Thiocyanation/Cyclization Cascade to Access Thiocyanato-Containing Benzoxazines

Due to the importance of SCN-containing heteroarenes, developing novel and green synthetic protocols for the synthesis of SCN-containing compounds has drawn much attention over the last decades. We reported here an electrochemical oxidative cyclization of ortho-vinyl aniline to access various SCN-containing benzoxazines. Mild conditions, an extra catalyst-free and oxidant-free system, and good tolerance for air highlight the application potential of this method.

Cu(II) carboxylate arene C─H functionalization: Tuning for nonradical pathways

We report carbon-hydrogen acetoxylation of nondirected arenes benzene and toluene, as well as related functionalization with pivalate and 2-ethylhexanoate ester groups, using simple copper(II) [Cu(II)] salts with over 80% yield. By changing the ratio of benzene and Cu(II) salts, 2.4% conversion of benzene can be reached. Combined experimental and computational studies results indicate that the arene carbon-hydrogen functionalization likely occurs by a nonradical Cu(II)-mediated organometallic pathway. The Cu(II) salts used in the reaction can be isolated, recycled, and reused with little change in reactivity. In addition, the Cu(II) salts can be regenerated in situ using oxygen and, after the removal of the generated water, the arene carbon-hydrogen acetoxylation and related esterification reactions can be continued, which leads to a process that enables recycling of Cu(II).

Synthesis of Spiro[benzo[d][1,3]oxazine-4,4'-isoquinoline]s via [4+1+1] Annulation of N-Aryl Amidines with Diazo Homophthalimides and O2

Synthesis of spiro[benzo[d][1,3]oxazine-4,4'-isoquinoline]s through a unique [4+1+1] annulation of N-aryl amidines with diazo homophthalimides and O₂ is presented. This unprecedented spirocyclization reaction features readily obtainable substrates, structurally and pharmaceutically attractive products, a cost-free and clean oxygen source, sustainable reaction medium, tolerance of a broad spectrum of functional groups, and an interesting reaction mechanism based on sequential C(sp²)-H/C(sp³)-H bond cleavage and oxygen insertion.

Iodine-mediated oxythiolation of o-vinylanilides with disulfides for the synthesis of benzoxazines

An efficient iodine-mediated oxythiolation of o-vinylanilides with disulfides was developed. By virtue of this method, a series of thio-tethered benzoxazine derivatives were synthesized in good to excellent yields. The reaction features high yields, is metal-free, and has a wide substrate scope.

An efficient iodine-mediated oxythiolation of o-vinylanilides with disulfides was developed. The reaction features high yields, is metal-free, and has a wide substrate scope.

C-centered radical-initiated cyclization by directed C(sp3)–H oxidative functionalization

C(sp3)–H functionalization is attracting constant attention. This review emphasizes C-centered radicals initiated cyclization strategies by directed C(sp3)–H oxidative functionalization since 2012.

The synthesis of sulfonated 4H-3,1-benzoxazines via an electro-chemical radical cascade cyclization

We achieved sulfonated 4H-3,1-benzoxazines under ambient conditions without any metals and external chemical oxidants via electrochemical radical cascade cyclizations.

Copper-Catalyzed Alkylarylation of Unactivated Alkenes: Synthesis of 3-Alkyl Indolines from N-Allyl Anilines and Alkanes

A rare example of C(sp³ )-H functionalization of simple alkanes with unactivated alkenes is presented. In the presence of a copper salt and di-tert-butyl peroxide (DTBP), N-allyl anilines underwent exo-selective alkylation/cyclization cascade with unactivated alkenic bonds as radical acceptors and simple alkanes as radical precursors, providing a direct access to 3-alkyl indolines. The present protocol features simple operation, broad substrate scope and great exo selectivity.

Benzylarylation of N-Allyl Anilines: Synthesis of Benzylated Indolines

An unprecedented benzylic C-H functionalization of methyl arenes across unactivated alkenes is presented. In the presence of MnCl₂·4H₂O and di- tert-butyl peroxide, N-allyl anilines underwent benzylation/cyclization cascade to give benzylated indolines, which are a previously unmet synthetic goal. This protocol features simple operation, broad substrate scope, and great exo selectivity.

Silver or cerium-promoted free radical cascade difunctionalization of o-vinylanilides with sodium aryl- or alkylsulfinates

An efficient cascade oxysulfonylation of o-vinylanilides with sodium aryl- or alkylsulfinates was developed for the synthesis of sulfonated benzoxazines.

Expedient stereospecific Co-catalyzed tandem C–N and C–O bond formation of N-methylanilines with styrene oxides

The Co(ii)-catalyzed stereospecific sequential C–N and C–O bond formation of styrene oxides with N-methylanilines has been developed. Optically active epoxides can be coupled with high enantiomeric purity.