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An efficient gold-catalyzed anti-Markovnikov cycloisomerization-initiated tandem reaction of Boc-protected indole tethered homopropargyl amides has been achieved. This method delivers a wide range of valuable bridged aza-[n.2.1] skeletons (n = 3–7) at room temperature with high diastereoselectivity and enantioselectivity by a chirality-transfer strategy. Moreover, the gold-catalyzed tandem reaction of homopropargyl alcohol is also achieved to produce the bridged oxa-[3.2.1] skeleton.

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 (i Pr2 -bimy)10 Br7 ]2+ (i Pr2 -bimy=1,3-diisopropylbenzimidazolin-2-ylidene) (1), was synthesized by direct reduction of AuSMe2 Cl and i Pr2 -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.

Transition-metal-catalyzed cascade cyclization initiated by intramolecular alkyne hydroamination has received considerable attention over the past decade and has been widely used in the rapid construction of a diverse array of valuable complex N-heterocycles. Recent progress in this area is reviewed with an emphasis on the cheap and environmentally benign copper-catalyzed cascade cyclization of terminal alkynes.

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 acro...

A series of gold-catalysed intramolecular anti-Markovnikov hydroamination-initiated azidation, allylation and heteroarylation reactions of chiral homopropargyl sulfonamides have been developed. Various enantioenriched 2,5-disubstituted pyrrolidines are obtained in moderate to excellent yields with excellent enantioselectivities and generally high diastereoselectivities.

Summary In recent years, significant advances have been made on photoredox-catalyzed N-radical addition to C-C unsaturated bond via N-H bond cleavage. However, these N-centered radical additions have so far been mostly limited to the alkenes, and to our knowledge, N-radical 5-endo-dig cyclizations of alkynes have been less exploited. Herein, we disclose an 5-endo-dig N-radical cascade cyclization of o-ethynylacetamides by photoredox catalysis involving rare radical cleavage of C-C triple bond, allowing the practical and controllable synthesis of a diverse array of valuable benzoxazinones and 2-hydroxy-3-indolinones in moderate to good yields under mild conditions. Furthermore, a mechanistic rationale for this radical cyclization cascade is supported by various control experiments and theoretical calculations.

Gold-catalyzed nucleophilic addition to terminal alkynes has received considerable interest in the past decade, as this chemistry offers a highly efficient and regioselective way for C$-$C, C$-$H and C$-$X bond formation. However, such a nucleophilic addition mainly involves a Markovnikov addition. In this short review, the recent progress of the gold-catalyzed 5- endo - dig cycloisomerization-initiated tandem reactions by utilizing the steric strain in ring formation to achieve an anti-Markovnikov regioselectivity was reviewed, including the scope of reactions, mechanism and synthetic applications.

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. Herein, we report a novel N-heterocyclic carbine-stabilized Au25 nanocluster with high thermal and air stabilities as a homogenous catalyst for cycloisomerization of alkynyl amines to indoles. The nanocluster, characterized as [Au25(iPr2-bimy)10Br7]2+ (iPr2-bimy=diisopropyl-benzilidazolium) (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 oC 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 gold in a cluster, and offers an opportunity to probe the catalytic mechanism at the atomic level.

Catalytic cycloisomerization-initiated cascade cyclizations of terminal alkynes have received tremendous interest, and been widely used in the facile synthesis of a diverse array of valuable complex heterocycles. However, these 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, where copper catalyzes both the hydroamination and Friedel-Crafts alkylation process. This method allows the practical and atom-economical synthesis of valuable bridged aza-[n.2.1] skeletons (n=3-6) with wide substrate scope, and excellent diastereoselectivity and enantioselectivity by a chirality-transfer strategy. Moreover, the mechanistic rationale for this novel cascade cyclization is also strongly supported by control experiments, and is distinctively different from the related gold catalysis.

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.

Ynamides are electron-rich heteroatom-substituted alkynes with C-C triple bond directly tethered to the amide group. Over the past decades, ynamides have proven to be versatile reagents for organic synthesis and have received extensive attention. Compared with the well-established ionic reactions of ynamides, radical-based ynamide reactions have been exploited relatively seldom. Herein, radical reactions of ynamides, classified by radical attack at the α-position and β-position of ynamides, are reviewed by highlighting the reaction selectivity, scope, mechanism, and applicability. The aim of this review is to provide a comprehensive summarization of these advances, casting light on the further development of ynamide chemistry.

A novel Brønsted acid-catalyzed oxidative C-H functionalization of alkynyl thioethers has been developed. This method allows the practical synthesis of valuable isothiochroman-3-ones in mostly moderate to good yields under mild reaction conditions and features a broad substrate scope and wide functional group tolerance. Moreover, this metal-free oxidation can also be used to promote formal N-H insertion involving an unexpected 1,2-sulfur migration, affording useful 1,4-benzothiazin-3-ones.

The asymmetric synthesis of chiral γ-lactams is difficult and laborious; typically requiring pre-functionalization of starting materials. Now, a highly efficient alternative approach employing direct C−H amidation via chiral hydrogen-bond-donor catalysts has been developed.

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.

An efficient yttrium-catalyzed tandem intermolecular hydroalkoxylation/Claisen rearrangement has been developed, providing various γ,δ-unsaturated amides in generally good to excellent yields. Importantly, high Z/E selectivity and diastereoselectivity were achieved. Other notable features of this method include widespread availability of the substrates, compatibility with a broad range of functional groups, and mild reaction conditions.

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 AuI/AuIII redox cycle promoted by visible-light photoredox catalysis.

Laneway is the important entity of mine, and it plays an important role in mine safety production. in this paper, firstly it studies the feasibility of the 3D visualization. through analyzing the characteristics and the related data of the laneway, it finally uses the method that along the center line to insert a series of profiles to achieve the modeling. This paper discusses the following aspects: for bend laneway use the segmentation method to achieve its sleek link, for profiles of different sizes of the entry sleek joining together, for crossing laneway use Bezier interpolation algorithm to implement its seamless integration. Finally it uses OpenGL in VC++ to implement the 3D laneway.

Based on the designing requirement of virtual car driving simultaion system, a collision detection algorithm based on the model projection point was proposed referring to Moore and Wilhelms' ideas of the virtual driving simulation system. The algorithm rationally distributes and minimizes the objects which are involved in calculation in different stages, decomposes the struction of scenes and re-organizes the the composition of modles. the experiments and analyses demonstrate that the new algorithm not only reduces the time of the collision detection, but also improves the accuracy of collision detection.

This paper proposes a new method of extracting feature points of hand. The method uses the center of mass of the hand as the match point to calculate the location information of the target based on Mathematical model of binocular visual positioning. The convex hull points of hand contour obtained by image segmentation can be used to identify the different gestures. Furthermore, a system with both functions of locating the three-dimensional position of hand and identifying the appropriate gestures is designed, which can serve as the interface to drive virtual hand to complete manipulation of grasping, moving and releasing virtual objects.