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A new Lewis acid catalysed formal hetero-[5+2] cycloaddition of 2,3-dihydro-1H-pyrroles to terminal alkynes is described. By employing a FeCl3 and BF3·OEt2 co-catalytic strategy, the ring-opening of 1-tosyl-2,3-dihydro-1H-pyrroles by selective cleavage of the C(sp2)–N bond and subsequent annulation have been achieved to access 1-tosyl-2,3-dihydro-1H-azepines with excellent regioselectivity, offering a new avenue for cycloaddition through the ring-opening of non-strained-ring-based units. [ABSTRACT FROM AUTHOR]

A new Rh(iii)-catalyzed oxidative bicyclization through C–H functionalization is presented. This reaction allows the selective assembly of diverse benzo[g]indoles from 4-arylbut-3-yn-1-amines and internal alkynes via a sequence of aromatic C(sp2)–H functionalization, cyclodimerization and nucleophilic cyclization. [ABSTRACT FROM AUTHOR]

A convenient and efficient method for the synthesis of furoxan derivatives from α-nitro-ketoximes and sulfonyl chlorides is reported. A wide variety of furoxan derivatives were smoothly obtained in good yields via a DABCO-mediated cascade sulfonylation/cyclization process under mild conditions. The usefulness of this method was also demonstrated by the conversions of the furoxan products into other promising compounds. [ABSTRACT FROM AUTHOR]

This study describes a new rhodium(III)-catalyzed [3+2] annulation of 5-aryl-2,3-dihydro-1H-pyrroles with internal alkynes using a Cu(OAc)2 oxidant for building a spirocyclic ring system, which includes the functionalization of an aryl C(sp2)H bond and addition/protonolysis of an alkene CC bond. This method is applicable to a wide range of 5-aryl-2,3-dihydro-1H-pyrroles and internal alkynes, and results in the assembly of the spiro[indene-1,2′-pyrrolidine] architectures in good yields with excellent regioselectivities. [ABSTRACT FROM AUTHOR]

An efficient dearomative (3 + 2) cycloaddition of para-quinamines and 2-nitrobenzofurans has been developed. This reaction proceeds smoothly under mild conditions and affords a series of benzofuro[3,2-b]indol-3-one derivatives in good to excellent yields (up to 98%) with perfect diastereoselectivities (all cases > 20:1 dr). The scale-up synthesis and versatile derivatizations demonstrate the potential synthetic application of the protocol. A plausible reaction mechanism is also proposed to account for the observed reaction process. This work represents the first instance of the N-triggered dearomative (3 + 2) cycloaddition of 2-nitrobenzofurans. [ABSTRACT FROM AUTHOR]

In this research, a metal-free diastereoselective formal 1,3-dipolar cycloaddition of N-2,2,2-trifluoroethylisatin ketimines and cyclopentene-1,3-diones which can efficiently lead to the desymmetrization of cyclopentene-1,3-diones is developed. With the developed protocol, a series of tetracyclic spirooxindoles containing pyrrolidine and cyclopentane subunits can be smoothly obtained with good results (up to 99% yield and 91:9 dr). Furthermore, the methodology can be extended to trifluoromethyl-substituted iminomalonate, and the corresponding formal [3+2] cycloaddition reaction affords bicyclic heterocycles containing fused pyrrolidine and cyclopentane moieties in moderate yields with >20:1 dr. The synthetic potential of the methodology is demonstrated by the scale-up experiment and by versatile transformations of the products. [ABSTRACT FROM AUTHOR]

Catalytic asymmetric dearomative [3+2] cycloaddition of α-imino γ-lactones with either 3-nitroindoles or 2-nitrobenzofurans by using a chiral copper complex as the catalyst was developed. A wide range of structurally diverse polyheterocyclic compounds containing spirocyclic-fused butyrolactone-pyrrolidine-indoline and butyrolactone–pyrrolidine–dihydrobenzofuran skeletons could be smoothly obtained with excellent results (>99:1 dr and 98% ee). The potential synthetic applications of this methodology were also demonstrated by the scale-up experiment and by the diverse transformations of one product. This method is characterized by high asymmetric induction, wide functional group tolerance and scalability, and attractive product diversification. [ABSTRACT FROM AUTHOR]

A new Rh-catalyzed reaction of 4-arylbut-3-yn-1-amines (I) with symmetrically 1,2-disubstituted acetylenes (II) gives rise to cross-bicyclization products (III), whilst the use of unsymmetrically disubstituted alkynes (IV) leads to a mixture of regioisomers (V) and (VI). [ABSTRACT FROM AUTHOR]

Comprehensive Summary: A visible‐light‐induced tandem radical intramolecular cyclization/arylation of quinoxalin‐2(1H)‐ones with bromodifluoroacetamides is described. This protocol allows efficient access to a variety of valuable α,α‐difluoro‐γ‐lactam‐fused quinoxalin‐2(1H)‐ones in moderate to good yields under metal‐free, mild and redox neutral reaction conditions. This strategy is tolerant of various functional groups and a broad range of substrates. The mechanism experiments suggested an involvement of 5‐exo‐trig cyclization and a radical process in this transformation. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: A visible‐light‐promoteded [3 + 2] cycloaddition reaction of 2H‐azirines with quinones has been developed under mild reaction conditions. The reaction provides a general and efficient strategy for the synthesis of the benzo[f]isoindole‐4,9‐diones scaffold via a tandem [3 + 2] cyclization/oxidative aromatization with molecular oxygen. Furthermore, preliminary studies for photocatalytic properties show that the benzo[f]isoindole‐4,9‐diones 3 can be used as photocatalysts in several organic transformations. [ABSTRACT FROM AUTHOR]

Using 1-thioaurones and 1-azaaurones as electron-deficient oxa-dienes, an organocatalytic asymmetric aromatizing inverse electron-demand [4+2] cycloaddition with γ-deconjugated butenolides and azlactones was developed. A wide range of optically active benzothiophene-fused δ-lactones and indole-fused δ-lactones were obtained with desirable outcomes (up to 94% yield, >99 : 1 dr and 99% ee). [ABSTRACT FROM AUTHOR]

In this study, visible‐light‐induced [3+2] cyclization reactions of hydrazones with hypervalent iodine diazo reagents as diazomethyl radical precursors are reported. Mild reaction conditions, a broad substrate scope, and excellent functional group compatibility were observed. Furthermore, the synthetic utility was demonstrated by gram‐scale synthesis and elaboration to several value‐added products. This protocol broadens the scope of diazo chemistry, and is applicable to the late‐stage functionalization of natural products. [ABSTRACT FROM AUTHOR]

An efficient asymmetric [4+2] cycloaddition of 1-((2-aryl)vinyl)naphthalen-2-ols and in situ generated ortho-quinone methides with chiral phosphoric acid as the catalyst was developed. This reaction enables the highly enantioselective synthesis of chiral polysubstituted chromanes bearing multiple contiguous stereogenic centers in excellent yields and stereoselectivities (up to 99% yield, >95 : 5 dr and >99% ee). [ABSTRACT FROM AUTHOR]

A new method for the cascade cyclization of 1,7-enynes with aromatic sulfonyl chlorides by using a low-cost and more abundant Cu catalyst is reported. [ABSTRACT FROM AUTHOR]