Enantioselective[3 t 2]cycloadditions of terminal allenoates withβ-sulfonyl-α,β-unsaturated ketones

A highly efficient and mild method for[3 t 2]cycloaddition ofβ-sulfonyl-α,β-unsaturated ketones with terminal allenoates was well-explored and developed.The reactions were successfully performed by applying multifunctional chiral phosphine P6 which was screened from eight chiral phosphorus reagents to finally result in a variety of enantioenriched sulfone-substituted cyclopentenes with two chiral centers(up to 81%yield with 94%ee).Moreover,2.5 mol%catalytic equivalents were proved to be feasible when this reaction was performed on a 10 mmol scale.

Design and Application of m-Hydroxybenzyl Alcohols in Regioselective(3+3)Cycloadditions of 2-Indolymethanols

A new class of m-hydroxybenzyl alcohols has been designed as competent three-carbon building blocks and achieved their applica-tion in 2-indolylmethanol-involved regioselective(3+3)cycloadditions under the catalysis of Br?nsted acids.By this appoach,a series of indole-fused six-membered cycloadducts have been synthesized in overall good yields(up to 98%)with excellent regioselectivity(all>95:5 rr),thus affording a powerful method for the construction of indole-fused six-membered rings.Moreover,a catalytic asymmetric version of this(3+3)cycloaddition has been preliminarily investigated,which revealed the potential of the reaction for constructing chiral indole-fused six-membered rings in an enantioselective manner.This work not only has accomplished the first design of m-hydroxybenzyl alcohols as competent reactants,but also represents the first application of m-hydroxybenzyl alcohols as three-carbon building blocks in cycloadditions.In addition,this work provides a good example for regioselective and C3-nucleophilic(3+3)cycloadditions of 2-indolylmethanols,which will substantially enrich the chemistry of 2-indolylmethanols.

Formal[2+1]Cycloadditions of a Metallacyclopentadiene Unit with Alkynes:Constructing Tetracyclic Conjugated Frameworks with Bridgehead Metals

Comprehensive Summary Metallacyclopentadienes play a vital role in transition-metal mediated and catalyzed cycloaddition reactions of alkynes.Though versatile reactions of metallacyclopentadienes with alkynes have been disclosed,[2+1]cycloadditions of metallacyclopentadienes and alkynes have never been discovered.In present work,we report the formal[2+1]cycloadditions of a metallacyclopentadiene unit with a broad scope of commercial alkynes,providing a facile strategy to construct tetracyclic conjugated compounds.The deuterated experiment indicates a metal vinylidene intermediate has been involved in[2+1]cycloaddition.Moreover,the electrophilic substitution reaction of the tetracyclic conjugated compound with the aid of density functional theory(DFT)calculated Fukui functions is investigated.

Progress in organocatalytic asymmetric (4+3) cycloadditions for the enantioselective construction of seven-membered rings

Chiral seven-membered ring systems such as seven-membered carbocycles and heterocycles are widely found in natural products and pharmaceuticals.Therefore,the catalytic enantioselective construction of such frameworks has evoked considerable interest in the field of chemistry.Among the various approaches,organocatalytic asymmetric(4+3)cycloadditions are highly effective for the enantioselective construction of seven-membered rings.Over the past two decades,substantial efforts have been devoted to this field and chemists have developed various organocatalytic asymmetric(4+3)cycloadditions.This review summarizes the progress in organocatalytic asymmetric(4+3)cycloadditions from 2003 to early 2022 and provides insights into challenging issues faced in this research field,enabling the future development of this field.

Switchable regioselectivity in amine-catalysed asymmetric cycloadditions

Subject Code:B02 With the support by the National Natural Science Foundation of China,a collaborative study by the research groups led by Prof.Chen Yingchun(陈应春)from Sichuan University and Dr.Ouyang Qin(欧阳勤)from the Third Military Medical University demonstrates switchable regioselective[6+2]。

Organocatalytic Enantioselective[8+4]Cycloadditions of Iso-benzofulvenes for the Construction of Bicyclo[4.2.1]nonanes

The[8+4]cycloaddition of indene-2-carbaldehydes with indole-2,3-quinodimethanes and pyrrolidone-3,4-dienes is described,affording indole and pyrrolidone annulated bicyclo[4.2.1]nonanes in a highly peri-,diastereo-,and enantioselective fashion in the presence of a secondary amine catalyst.This reaction,which proceeds through catalytically generated isobenzofulvenes,represents the first asymmetric version of high-order[8+4]cycloaddition.

Catalytic asymmetric dipolar cycloadditions of indolyl delocalized metal-allyl species for the enantioselective synthesis of cyclopenta[b]indoles and pyrrolo[1,2-α]indoles

The development of novel synthons and efficient methods to synthesize chiral polycyclic indoles has been a hot topic in organic synthesis and medicinal chemistry owing to their broad applications in medicines,pesticides,and other functional molecules.Here,we disclosed novel indolyl substituted metal-allyl zwitterionic intermediates through the decarboxylation of conveniently available vinyl indoloxazolidones,which could be regarded as two types of dipolar species through the anionic delocalization.The palladium-π-allyl species tended to serve as an all-carbon 1,3-dipole in the asymmetric[3+2]cycloaddition with electrondeficient alkenes,which furnished polysubstituted cyclopenta[b]indoles with high regio-and stereoselectivities.Meanwhile,the iridium-π-allyl species was recognized as an aza-1,3-dipole in asymmetric[3+2]cycloaddition with in situ generated C1 ammonium enolates,affording pyrrolo[1,2-α]indoles with high diastereo-and enantioselectivities.In addition,the dipolar cycloadditions could be easily scaled-up and several synthetic transformations of the cycloadducts were demonstrated for the rapid synthesis of diverse chiral polycyclic indoles.

Phase-mediated controllable intramolecular and intermolecular photocycloadditions assisted by supramolecular templates

Understanding and controlling supramolecular template effect assembly via a photochemical reaction in different solid and solution phases is one of the main topics in photochemistry. Here, an interesting case of phase-mediated controllable intramolecular/intermolecular photochemical [2+2] cycloadditions assisted by supramolecular templates was demonstrated. Direct irradiation of the complexes in solution yields intramolecular photoproducts exclusively, whereas exposure of the solid powder sample under the same conditions yields intermolecular dinuclear species quantitatively. The nature of the phase and supramolecular interaction affects the geometrical arrangements of the metallacycles, leading to different cycloaddition products under photoirradiation. The crystal structures of different products were investigated by single-crystal X-ray diffraction, nuclear magnetic resonance(NMR) spectrometry, and electrospray ionization mass spectrometry(ESI-MS).

Cycloadditions of 1-iminylphosphirane complexes with allenes

A cascade carbonylative ring expansion and [2+2]/[4+2] cycloaddition of strained 1-iminylphosphirane complexes with aryl allenes were reported.The carbonylative ring expansion of 1-iminylphosphirane complexes provides an azaphosphacyclohexone complex intermediate with a C=P double bond.The following [2+2] or dearomatic [4+2] cycloaddition of this intermediate with allenes is modulated by the aryl substituents on the imino carbon.The regioselective [2+2] cycloaddition with 1,1-diarylallene provides an entry to bicyclo[4.2.0]octan-4-one skeletons featuring a four-membered phosphacyclobutane moiety.While dearomatic [4+2] cycloaddition was preferred with less aromatic naphthalene and yielded octahydrochrysene skeleton containing heteroatoms.

Intramolecular (4+3) cycloadditions of nitrogen-tethered epoxy enosilanes for the synthesis of heteropolycycles

Furans bearing epoxy enolsilane units via a tether that incorporates a nitrogen heteroatom,undergo intramolecular(4+3)cycloadditions to generate bis-heteroatomic polycyclic adducts having piperidine moieties in their frameworks.The cycloadducts,ultimately derived from furfural,a renewal chemical feedstock,are obtained with up to 4:1 dr and with ee retained from the epoxide.

Stereoconvergent and stepwise 1,3-dipolar cycloadditions of nitrile oxides and nitrile imines

The first example of stereoconvergent 1,3-dipolar cycloaddition of nitrile oxides and nitrile imines with E/Z isomeric mixture of electron-deficient olefins is reported,delivering isoxazolines and pyrazolines bearing two vicinal stereogenic tertiary and trifluoromethylated quaternary carbon centers with perfect regioand diastereoselectivities.The possibility of concerted cycloaddition/epimerization sequence under basic condition to form the thermodynamically stable diastereomers is excluded through some control experiments and DFT calculations,and a stepwise mechanism is proposed.

Nickel-Catalyzed Regiodivergent Asymmetric Cycloadditions of α,β-Unsaturated Carbonyl Compounds

Regiodivergent asymmetric cycloadditions from the same set of starting materials offer interesting opportunities for rapid construction of optically active cyclic molecules with structural diversity.However,this remains a challenging task due to the difficulty of simultaneously controlling the regio-,diastereo-,and enantioselectivity in the ring formation processes.To address this long-standing problem.

Carbolong Chemistry: Planar CCCCX-Type (X = N, O, S) Pentadentate Chelates by Formal [3+1] Cycloadditions of Metalla-Azirines with Terminal Alkynes

Three-membered unsaturated rings have been widely utilized in organic synthesis due to their inherent highly strained structures.Although much research has been applied to ring-expansion reactions of such strained ring systems,pathways other than[3+2]cycloadditions have rarely been observed in their reactions with alkynes,and to date,no[3+1]cycloadditions of isolated three-membered unsaturated rings with alkynes have been reported.Here we demonstrate an unprecedented[3+1]cycloaddition in which a fused metalla-azirine is used as a template to generate a series of planar CCCCX-type(X=N,O,S)pentadentate carbolong complexes 3–6.A series of substituted alkynes was tested for further exploration of the scope and mechanism for the[3+1]cycloaddition reactions.Complexes 3–6 represent rare examples of planar pentadentate complexes that assemble fourπ-conjugated fused rings by one bridgehead atom.These novel complexes are thermally stable in air and absorb ultraviolet,visible,and near-infrared light,and thus are potentially applicable in photoelectric devices and pharmaceuticals.

Mesoporous poly(ionic liquid)s with dual active sites for highly efficient CO_(2)conversion

Atmospheric CO_(2)concentrations are soaring due to the continued use of fossil fuels in energy production,an anthropogenic activity that is playing a leading role in global warming.Thus,research aimed at the capture and conversion of CO_(2)into value-added products,such as cyclic carbonates,is booming.While CO_(2)is an abundant,cheap,non-toxic,and readily accessible Cl feedstock,its thermodynamic stability necessitates the development of highly efficient catalysts that are able to promote chemical reactions under mild conditions.In this work,a novel mesoporous poly(ionic liquid)with dual active sites was synthesized through a facile method that involves co-polymerization,post-synthetic metalation,and supercritical CO_(2)drying.Due to a high density of nucleophilic and electrophilic sites,the as-prepared poly(ionic liquid),denoted as P2D-4BrBQA-Zn,offers excellent performance in a CO_(2)cycloaddition reaction using epichlorohydrin as the substrate(98.9%conversion and 96.9%selectivity).Moreover the reaction is carried out under mild,solvent-free,and additive-free conditions.Notably,P2D-4BrBQA-Zn also efficiently promotes the conversion of various other epoxide substrates into cyclic carbonates.Overall,the catalyst is found to have excellent substrate compatibility,stability,and recyclability.

Rhodium Catalyzed [2π + 2π + 2π]-Cycloaddition of Alkynyl-Ynamides and Carbon Disulfide to Indolo-Thiopyrane Thiones

The synthesis of new indoloannulated thiopyranethiones is reported. The key-step is a rhodium-catalyzed [2 + 2 + 2]-cycloaddition of alkynyl-ynamides with carbon disulfide to close the pyrrole and the thiopyranethione rings simultaneously. A violet idolothiopyrane thione or a mixture of the violet and a red isomer result from [RhCl(C8H14)2]2/3BINAP catalyzed cycloadditions, the regiochemistry is controlled by the substitution pattern on the alkynyl-ynamide.

卡宾单重态与乙烯环加成反应中的轨道作用图象

卡宾单重态与乙烯环加成反应已有很多计算工作和轨道作用的解释。由于该反应的C2v,对称性反应道的反应为禁阻反应,故反应取先由分子平面互相平行而后转向互相垂直的Cs对称性反应道。本文拟就这个反应过程中前线轨道的相互作用及变化情况提出一个简化模型,以期得到对全过程的清晰面象。1.正则轨道图象:

Protic vs aprotic ionic liquid for CO2 fixation:A simulation study

The cycloaddition of CO2 with epoxides catalyzed by ionic liquids(ILs)has been a widely ongoing studied hot topic over the years.Recent experimental research has shown that the protic ionic liquids(PILs)behave stronger hydrogen proton donating ability than aprotic ionic liquids(APILs),and can effectively catalyze the cycloaddition of CO2.Unfortunately,the mechanistic explanation remains primarily unraveled.Herein,a detailed simulation study on the cycloaddition reaction catalyzed by PIL([HDBU][Mim])in comparison with APIL([MeDBU][Mim])re-action catalysts was conducted,including the three-step route(ring-opening of PO(propylene oxide),insertion of CO2 and ring-closure of propylene carbonate(PC))and two-step route(simultaneously ring-opening of PO and addition of CO2,and then ring-closure of PC).Based on the activation energy barrier of the rate-determining step,PIL preferentially activates PO as the optimal route for the reaction with the energy barrier of 23.2 kcal mol-1,while that of APIL is 31.2 kcal mol-1.The role of[HDBU]+in the reaction was also explored and found that the direct formation of intermolecular hydrogen bond(H-bond)between[HDBU]+and the reactants(PO+CO2)was unfavorable for the reaction,while the cooperation with the anion[Mim]-to assist indirectly was more conducive.To fully consider the reaction microenvironment of ILs,ONIOM calculation was used to study the solvent effect.At last,the above conclusions were further verified by the analysis of intermediates with charge,non-covalent interaction(NCI),and atoms in molecules(AIM)methods.The computational findings show that ILs studied in this work have dual functions of catalyst and solvent,enabling a microscopic understanding of the ILs catalyst for CO2 utilization as well as providing guidance for the rational design of more efficient ILs-based catalysts.

Salen-Cu(Ⅱ)@MIL-101(Cr)as an efficient heterogeneous catalyst for cycloaddition of CO2 to epoxides under mild conditions

A double active center system, namely Salen-Cu(Ⅱ)@MIL-101(Cr), was successfully synthesized via the"ship in a bottle" approach, which acted as a bifunctional material for both capture and conversion of CO_2 in a single process. For the first time, Salen-Cu(Ⅱ)@MIL-101(Cr) catalyst was developed for the synthesis of propylene carbonate from CO_2 and propylene oxide under room temperature and ambient pressure with a yield of 87.8% over 60 h. Furthermore, the reaction mechanism was also discussed.

Studies on New Additions to 5-Methoxy-2 (5H)-Furanone: 1, 4-Addition of Grignard Reagents, and 1,3-Dipolar Cycloaddition of Silyl Nitronates

Addition reaction of Grignard’s reagent to 5-methoxy-2(5H)-furanone 1 was accomplished, which provided a new possible route for synthesizing β-alkyl-γ-alkyloxy-γ-butyrolactone. A novel concise method of preparing fused heterocyclic compounds was offered by 1,3-dipolar cycloaddition reaction of silyl nitronates to 1.

Facile preparation of bi-functional iron doped mesoporous materials and their application in the cycloaddition of CO2

Two kinds of bi-functional transition metal doped mesoporous materials(Fe-HMS and Fe-MCM-41) are prepared using one-step hydrothermal method and then treated with hydrochloric acid ethanol solution.The N2 adsorption and HRTEM results show that both of Fe-HMS and Fe-MCM-41 possess mesoporous structure. The UV–vis results suggest that the Fe species are mainly located within the framework. The basicity of as-prepared samples was studied by temperature programmed desorption using CO2 as probe molecule(CO2-TPD). The catalytic performance of Fe-HMS and Fe-MCM-41 in CO2 cycloaddition largely depends on the amount of the accessible basic sites. The acid–base active sites, framework Fe and PDDA species cooperatively catalyze the CO2 cycloaddition for the production of cyclic carbonates under the condition without any co-catalyst. The conversion of epichlorohydrin(ECH) is 97.4% and the selectivity of chloropropene carbonate is 92.9% under optimal conditions. The approximate rate constant of cycloaddition reaction of CO2 with ECH under optimum reaction temperature is calculated. It is worth noting that the Fe-HMS material shows superior reusability than Fe-MCM-41. In addition, this work provides a facile way on the synthesis of bi-functional acid–base heterogeneous catalyst with outstanding catalytic performance for the fixation of CO2.