A new method for the nitrative spirocyclization of alkynes is described. This method involves the oxidative difunctionalization of alkynes initiated by a radical attack pathway using t-BuONO (tertbutyl nitrite) combined with water as the nitro source and TEMPO [(2,2,6,6-tetramethyl-piperidin-1-yl)oxyl] as the initiator, and it represents a new example of oxidative alkyne difunctionalization via the formation of C À N/C À C bonds for the assembly of nitroalkene unit-containing spirocycles.

The novel CuCl2‐catalyzed title reaction of enynes has been developed for synthesizing substituted naphthoquinones (see scheme; DMA=dimethylacetamide). The method represents the first example of a copper‐catalyzed enyne oxidative cyclization for constructing 1,4‐naphthoquinones by the incorporation of two oxygen atoms into the organic framework from molecular oxygen and water.

Difunctionalization of alkenes has become a powerful tool for quickly increasing molecular complexity in synthesis. Despite significant progress in the area of alkene difunctionalization involving the incorporation of a nitrogen atom across the C–C double bonds, approaches for the direct 1,2-carboamination of alkenes to produce linear N-containing molecules are scarce and remain a formidable challenge. Here we describe a radical-mediated oxidative intermolecular 1,2-alkylamination of alkenes with alkyl nitriles and amines involving C(sp3)–H oxidative functionalization catalysed by a combination of Ag2CO3 with iron Lewis acids. This three-component alkene 1,2-alkylamination method is initiated by the C(sp3)–H oxidative radical functionalization, which enables one-step formation of two new chemical bonds, a C–C bond and a C–N bond, to selectively produce γ-amino alkyl nitriles.

A new oxidative coupling of unactivated terminal alkenes with amides using peroxides is described, in which mono- and difunctionalization of alkenes are selectively achieved. In this reaction with amides, the chemoselectivity toward the functionalization of the C(sp(3))-H bonds adjacent to the nitrogen atom or the functionalization of the carbonyl C(sp(2))-H bonds across alkenes relies on the reaction conditions.

A new route is presented for the selective assembly of isoquinolines and indenes by rhodium-catalyzed tandem cyclization of benzylidenehydrazones with internal alkynes. This method involves the selective cleavage of the N-N bond and the C═N bonds and is dependent on the substituents of the benzylidenehydrazone.

A novel palladium-catalyzed methylation protocol for the synthesis of methyl-functionalized internal alkynes has been established. This methylation method is achieved through a C(sp)-C(sp(3)) bond formation process and represents a new synthetic application of sulfonium ylides.

A new transition metal‐free oxidative coupling of unactivated terminal alkenes with aldehydes and hydroperoxides in the presence of 10 mol% potassium tert‐butanolate (t‐BuOK) is described thereby realizing trifunctionalization of alkenes toward 2,3‐epoxy ketones. This method is applicable to a wide range of aldehydes, including aryl and alkyl aldehydes, with excellent functional group tolerance, and provides for the one‐step assembly of 2,3‐epoxy ketones.magnified image

O-labeling experiment shows that two oxygen atoms in the product system are from water.Keywords: alkynes;b enzoxazines;c ycloaddtion;n itrites;radical reaction Thec ycloaddition reactionh as become one of the most important methodsi ns ynthesis to buildd iverse carbo-andh eterocyclic systems. [1,2] Among these approaches, annulationswith alkynesoccupyaprivileged position and have been well exploited. [1,2] However, many classic approaches sufferf rom the cost of the catalytic systems,h arsh reactionc onditions and/or limited substrate scope.A lternatively,t he transition metal-catalyzed aromatic C(sp 2 ) À Hf unctionalization strategy, in combination with subsequent annulation with alkynes,h as become particularly attractiveb ecause it avoids the prior preparation of activated substrates with the associated reduction of chemical waste generated, thereby streamlining organic synthesis in am ore step-anda tom-economic fashion. [2][3][4] One typical class of these transformationsi st he [4+ +2] annulation of substrates containingc leavable C À H/ N À Y( Y = H, O, N) bonds, [3] C À H/O À Hb onds, [4] or C À Hb ond/C À C p-bonds [5] with alkynes leading to diverse heterocycles.H owever, the majority of these transformationsa re also restricted by the requirement for expensivemetal catalytic systems.Herein, we report an ew metal-free radical-mediated [4+ +2] annulation protocolt oa ssemble benzo[e]-[1,2]oxazin-4-ones (Scheme 1), in which internal arylalkynes serve as 4-carbon units for reactionw ith tBuONO throught he formation of aC =Od ouble bond, aC =Nd ouble bond and aC À Os ingle bond. This method achieves the addition of t-BuONO [5] across the C Ct riple bond, followed by ah ydration, isomerizationa nd aromaticC ( sp 2 ) À Ho xidation [6] sequence,a nd represents the first example of O-aryloxime ethers keleton construction via C À Ho xidation. [7] Notably,t he products,b enzoxazines,a re important heterocyclic scaffolds that occur in manyn atural products, pharmaceuticals and materials. [8] Our studies began with an investigation of reaction conditions for the [4+ +2] annulation of 1,2-diphenylethyne (1a)w ith t-BuONO (Table 1). Extensive screeningo fv arious reactionp arameters,i ncluding the effect of reactiont emperature,n itrites,s olvents and H 2 O, revealedt hat the reaction of alkyne 1a with 5equiv. of t-BuONO and 4equiv.o fH 2 Oi nD MSO at 100 8 8Cf or 12 hw as optimal to furnish the desired benzoxazine 2a in 66% yield (entry 1).[9] Ther esults showedt hat the reactiont emperature affected the reaction:t he yield of 2a decreasedf rom 66% at 100 8 8C to 28% at 80 8 8Ca nd to 51% at 120 8 8C( entries 1-3). While ad ecrease in the loading of t-BuONO to 3equiv. was not beneficial to the formationo fb enzoxazine 2a (34% yield;e ntry 4), the addition of 8equiv. t-BuONO gave the identical results to that with 5equiv. t-BuONO (entry 5). Subsequently,t hree Scheme1.Radical-mediated [4+ +2] annulation.