Surface organic ligands playac ritical role in stabilizing atomically precise metal nanoclusters in solutions. However,itisstill challenging to prepare highly robust ligated metal nanoclusters that are surface-active for liquid-phase catalysis without any pre-treatment. Now,a nN -heterocyclic carbene-stabilized Au 25 nanocluster with high thermal and air stabilities is presented as ah omogenous catalyst for cycloisomerization of alkynyl amines to indoles.T he nanocluster, characterized as [Au 25 ( i Pr 2 -bimy) 10 Br 7 ] 2+ ( i Pr 2 -bimy = 1,3-diisopropylbenzimidazolin-2-ylidene) (1), was synthesized by direct reduction of AuSMe 2 Cl and i Pr 2 -bimyAuBr with NaBH 4 in one pot. X-rayc rystallization analysis revealed that the cluster comprises two centered Au 13 icosahedra sharing av ertex. Cluster 1 is highly stable and can survive in solution at 80 8 8Cf or 12 h, which is superior to Au 25 nanoclusters passivated with phosphines or thiols.DFT computations reveal the origins of both electronic and thermal stability of 1 and point to the probable catalytic sites.T his work provides new insights into the bonding capability of N-heterocyclic carbene to Au in ac luster,a nd offers an opportunity to probe the catalytic mechanism at the atomic level.

Ynamides are special alkynes bearing an electron-withdrawing group on the nitrogen atom, and they have been extensively studied over the past decade. However, the addition of functional groups across ynamides in these transformations typically occurs at the α-position of the ynamide because of the strong polarization of the alkynyl moiety. Studies of umpolung transformations in ynamide chemistry may not only discover organic reactions but also lead to divergent organic syntheses, thus significantly enriching ynamide chemistry. This review summarizes four main strategies utilized to achieve reversal of the regioselectivity, including the ring strain factor, metal–carbonyl (or sulfonyl) chelation, and base-mediated and radical-initiated addition.

Isoxazoles, as masked 1,3-dicarbonyl equivalents, have proven to be versatile building blocks and pivotal intermediates for the construction of a variety of useful azacycles with molecular complexity. As a result, a range of new reactions have been discovered based on isoxazoles in the past decade. However, the relevant reactions of isoxazoles with alkynes have seldom been explored. In this review, we will focus on the recent progress in the transition-metal-catalyzed formal annulations for the efficient synthesis of N-heterocycles between alkynes and isoxazoles by highlighting their specificity and applicability, and the mechanistic rationale is presented where possible.

Surface organic ligands play a critical role in stabilizing atomically precise metal nanoclusters in solutions. However, it is still challenging to prepare highly robust ligated metal nanoclusters that are surface‐active for liquid‐phase catalysis without any pre‐treatment. Now, an N‐heterocyclic carbene‐stabilized Au25 nanocluster with high thermal and air stabilities is presented as a homogenous catalyst for cycloisomerization of alkynyl amines to indoles. The nanocluster, characterized as [Au25(iPr2‐bimy)10Br7]2+ (iPr2‐bimy=1,3‐diisopropylbenzimidazolin‐2‐ylidene) (1), was synthesized by direct reduction of AuSMe2Cl and iPr2‐bimyAuBr with NaBH4 in one pot. X‐ray crystallization analysis revealed that the cluster comprises two centered Au13 icosahedra sharing a vertex. Cluster 1 is highly stable and can survive in solution at 80 °C for 12 h, which is superior to Au25 nanoclusters passivated with phosphines or thiols. DFT computations reveal the origins of both electronic and thermal stability of 1 and point to the probable catalytic sites. This work provides new insights into the bonding capability of N‐heterocyclic carbene to Au in a cluster, and offers an opportunity to probe the catalytic mechanism at the atomic level.

Described herein is an organocatalytic enantioselective desymmetrizing cycloisomerization of arylsulfonyl‐protected ynamide cyclohexanones, representing the first metal‐free asymmetric Conia‐ene‐type carbocyclization. This method allows the highly efficient and atom‐economical construction of a range of valuable morphans with wide substrate scope and excellent enantioselectivity (up to 97 % ee). In addition, such a cycloisomerization of alkylsulfonyl‐protected ynamide cyclohexanones can lead to the divergent synthesis of normorphans as the main products with high enantioselectivity (up to 90 % ee). Moreover, theoretical calculations are employed to elucidate the origins of regioselectivity and enantioselectivity.

A novel dual gold/photoredox-catalyzed bis-arylative cyclization of chiral homopropargyl sulfonamides with diazonium salts has been developed, allowing the facile synthesis of various enantioenriched 2,3-dihydropyrroles in generally moderate to good yields with excellent enantioselectivities under very mild conditions without using any strong oxidants. The reaction is proposed to undergo an Au/Au redox cycle promoted by visible-light photoredox catalysis.

Catalytic cycloisomerization-initiated cascade cyclizations of terminal alkynes have received tremendous interest, and been widely used in the facile synthesis of adiverse arrayof valuable complex heterocycles.H owever,t hese tandem reactions have been mostly limited to noble-metal catalysis,and are initiated by an exo-cyclization pathway. Reported herein is an unprecedented copper-catalyzed endo-cyclization-initiated tandem reaction of indolyl homopropargyl amides,w here copper catalyzesb oth the hydroamination and Friedel-Crafts alkylation process.This method allows the practical and atomeconomical synthesis of valuable bridged aza-[n.2.1] skeletons (n = 3-6) with wide substrate scope,and excellent diastereoselectivity and enantioselectivity by ac hirality-transfer strategy. Moreover,t he mechanistic rationale for this novel cascade cyclization is also strongly supported by control experiments, and is distinctively different from the related gold catalysis.Supportinginformation and the ORCID identification number(s) for the author(s) of this article can be found under: https://doi.

A novel gold-catalyzed tandem cycloisomerization/hydrogenation of chiral homopropargyl sulfonamides has been developed. Various enantioenriched pyrrolidines can be obtained in excellent yields and excellent enantioselectivities by combination of chiral tert-butylsulfinimine chemistry with gold catalysis. Importantly, this represents the first example of a pyrrolidine synthesis from homopropargyl sulfonamide.