ASYMMETRIC 1,3-DIPOLAR CYCLOADDITION REACTION BY A CHIRAL SOURCE,5-(1-MENTHYLOXY)-2(5-H)-FURANONE

5-(1-Menthyloxy)-2(5-H)-furanone is used as s chiral dipolarophile for thermal asymmetric 1,3-dipolar cycloaddition reaction with C-phenyl-N-phenyl nitrone to give the diastereomerically pure cycloaddition product.

Study on Unexpected Cycloaddition Reactions of Imines with THF

An unexpected tricyclic compound 2,3,3a,4,5,9b-hexahydrophenylfuro[3.2-c] quinoline 4 and its aromatized product 6 were obtained when the cycloaddtion of imine 1 and substituted norbornene 2 was carried out in THF with a catalytic amount of boron trifluoride. The structures of the products were determined by spectral data and the mechanism of reaction was substantiated by the imitation reaction.

A FACILE SYNTHESIS OF 2-TRIFLUOROMETHYLPYRROLE VIA 1,3-DIPOLAR CYCLOADDITION REACTION OF 2-TRIFLUOROMETHYLOXAZOLONE AND THE ACTIVATED CARBON-CARBON MULTIPLE BOND

The 1.3-dipolar cycloaddition reaction of 2-trifluoromethyl- oxazolone and the activated carbon-carbon multiple bond was studied and gave a convenient way to synthesize 2-trifluoromethylpyrrole derivatives.

The Cycloaddition Reaction of Lawesson's Reagent with 1,3-Dienes

Lawesson's reagent undergoes [2 + 4] cycloaddition reaction with 2-methyl-1, 3-butadiene,cyclopentadiene to yield heterocycles 4 and 5, respectively.

N-Arylindne 1,4-Cycloaddition Reaction.Preparation of Substituted Hexahydrofurol[3,2-c]quinolines

Lewis acid catalyzed cycloaddition reactions of N-arylideneaniline Ⅰ with 2,3-dihydrofuran Ⅱ gave a pair of epimers d1-2, 3, 3a, 4, 5, 9b-hexahydro-4-arylfuro [3,2-c]quinolines Ⅲ and Ⅲ) and a few of their corresponding aromatized compounds Ⅳ.

MHEORETICAL STUDIES ON THE REACTION MECHANISMS OF CYCLOADDITION REACTIONS BETWEEN KETENE OR SUBSTITUTED KETENES AND CYCLOPENTADIENE

The cycloaddition reactions between ketene or substituted ketenes and cyelopentadiene have been studied theoretically by means of the semiempirical AMI method.Three different substituted ketenes have been selected and ten transition states,corresponding to different approach geometries have been located and characterized,The regioselectivity and stereoselectivity of the reactions are correctly predicted by the calculations and the reaction mechanisms are analyzed in terms of electronic and steric effects of the substitutents on the reacting ketene and cyc-lopentadiene.

The cycloaddition reaction of ethylene and methane mediated by Ir^(+) to generate a half-sandwich structure Ir HCp^(+)

The cycloaddition reactions of methane and ethylene mediated by Ir^(+) have been designed and studied by the techniques of mass spectrometry in conjunction with theoretical calculations.Studies have shown that Ir^(+) can mediate the cycloaddition reaction of CH4and two C_(2)H_(4) to generate a half-sandwich structure IrHCp^(+)(Cp=η^(5)-C_(5)H_(5))including pentamethylcyclopentadienyl ligand by continuous dehydrogenation reaction with the forming of three C-C bonds and seven C-H bonds.The orbital analysis indicates the mechanism of the cyclization reaction to generation of pentamethylcyclopentadienyl ligand with odd number carbon atom depends on the overlap ofπorbitals in-C_(2)H_(2) and carbene,which is more difficult than the forming of cyclobutadiene ligand and benzene.This study may help to understand the reaction mechanism in the cycloaddition reactions of organic compounds,which will be useful to guide the rational design of new catalysts with tailored selectivity and increased efficiency.

Theoretical Study on the Mechanism of the Cycloaddition Reaction between Dichloromethylene Germylene and Ethylene

The mechanism of a cycloaddition reaction between singlet dichloromethylene germylene and ethylene has been investigated with B3LYP/6-31G＊ method, including geometry optimization and vibrational analysis for the involved stationary points on the potential energy surface. Energies for the involved conformations were calculated by CCSD（T）//B3LYP/6-31G＊ method. On the basis of the surface energy profile obtained with CCSD（T）// B3LYP/6-31G＊ method for the cycloaddition reaction between singlet dichloromethylene germylene and ethylene, it can be predicted that the dominant reaction pathway is that an intermediate INT1 is firstly formed between the two reactants through a barrier-free exothermic reaction of 61.7 kJ/mol, and the intermediate INT1 then isomerizes to an active four-membered ring product P2.1 via a transition state TS2, an intermediate INT2 and a transition state TS2.1, in which energy barriers are 57.7 and 42.2 kJ/mol, respectively.

Synthesis of Dispirocyclopentyl-3,3＇-bisoxindoles via Domino Cycloaddition Reactions of 4-Dimethylaminopyridinium Bromides with 3-Phenacylideneoxindoles

The base mediated cycloaddition reactions of 4-dimethylamino-l-phenacylpyridinium bromides with two mo- lecular 3-phenaeylideneoxindoles in methylene dichloride afforded functionalized dispirocyclopentyl-3,3＇-bisoxin- doles in good yields and with high diastereoselectivity. The similar cycloaddition reactions of 1-（N,N-dialkylcarba- moylmethyl） and 1-cyanomethyl 4-dimethylamino-pyridinium bromide in refluxing ethanol in the presence of triethylamine a/so resulted in dispirocyclopentyl-3,3＇-bisoxindoles with high diastereoselectivity. The stereochemis- try of dispirocyclopentyl-3,3＇-bisoxindoles was elucidated on the basis of ^1H NMR data and single crystal struc- tures.

Studies on Different Cycloaddition Reactions Catalyzed by ZnCl_2

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Stereocontrol of the Schiff Base of Substituted Benzaldehyde to Staudinger Cycloaddition Reaction

Syntheses of 4 novel chiral azetidin 2 one derivatives, which were characterized by 1H NMR, IR, specific rotation and elemental analysis, through Staudinger cycloaddition reaction of Schiff base of benzaldehyde with chlorine substitution at different position in benzene ring, were described. For the first time, this type of 3 S ,4 R configuration azetidin 2 one mono^crystals with many chiral centers [(3 S ,4 R ) 3 hydroxy N [( S ) (1 phenyl)ethyl ] 4 (2′ chlorophenyl) azetidin 2 one mono^crystal] were obtained, the structures of which were determined by X ray dif fraction analysis. The effects of Schiff base of benzaldehyde with chlorine subs titu tion at different position in benzene ring on stereoselectivity of Staudinger cy cloaddition reaction products were discussed and the results are showed as below : 2 chlorophenyl Schiff base favored to yield 3 S ,4 R configuration prod uct, but 4 chlorophenyl Schiff base favored to yield 3 R ,4 S configuration produc t. The re action orientation of 2,4 dichlorophenyl Schiff base was determined by corporat e effect of 2 and 4 chlorine, and that of the 4 chlorine was more obvious. In co ntrast to 4 chlorophenyl, although the main product was 3 R ,4 S configur ation, 3 chlorophenyl owned lower selectivity.

Features of Mechanism of Cycloaddition Reaction between Me2Ge=Sn:and Ethylene

X2Ge=Sn:(X=H,Me,F,Cl,Br,Ph,Ar…)are new species of chemistry.The cycloaddition reaction of X2Ge=Sn:is a new study field of stannylene chemistry.To explore the rules of cycloaddition reaction between X2Ge=Sn:and the symmetric p-bonded compounds,the cycloaddition reactions of Me2Ge=Sn:and ethylene were selected as model reactions in this paper,and the mechanism was investigated for the first time here using the MP2 theory together with the 6-311++G**basis set for C,H and Ge atoms and the LanL2dzbasis set for Sn atoms.From the potential energy profile,it could be predicted that the reaction has one dominant reaction channel.The reaction rule present is that the 5p unoccupied orbital of Sn in Me2Ge=Sn:and theπorbital of ethylene form a p→p donor–acceptor bond,resulting in an intermediate which,due to its instability,makes itself isomerize into a four-membered Ge-heterocyclic ring stannylene.Because the 5p unoccupied orbital of Sn atom in the four-membered Ge-heterocyclic ring stannylene and theπorbital of ethylene form a p→p donor-acceptor bond,the four-membered Ge-heterocyclic ring stannylene further combines with ethylene to get another intermediate.Because the Sn atom in this intermediate exhibits sp3 hybridization after transition state,the intermediate isomerizes to a Ge-heterocyclic spiro-Sn-heterocyclic ring compound.The research result indicates the laws of cycloaddition reaction between X2Ge=Sn:and the symmetricπ-bonded compounds.This study opens up a new research field for stannylene chemistry.

Theoretical Study of the Mechanism of Cycloaddition Reaction between Silylene Silylene （H2Si=Si：） and Acetone

The mechanism of the cycloaddition reaction between singlet silylene silylene （H2Si = Si：） and acetone has been investigated with the CCSD （T）//MP2/6-31 G＊ method, According to the potential energy profile, it can be predicted that the reaction has two competitive dominant reaction channels. The present rule of this reaction is that the [2 ＋ 2] cycloaddition reaction of the two ^-bonds in silylene silylene （H2Si=Si：） and acetone leads to the formation of a four-membered ring silylene （E3）. Because of the unsaturated property of Si： atom in E3, it further reacts with ace- tone to form a silicic bis-heterocyclic compound （P7）. Simultaneously, the ring strain of the four-membered ring silylene （E3） makes it isomerize to a twisted four-membered ring product （P4）.

AB INITIO STUDIES ON THE REACTION MECHANISH OF CYCLOADDITION OF KETENE AND FORMALDEHYDE

The cycloaddition reaction of ketene and formaldehyde,lesding to 2- oxetanone,has been studied theoretically by means of RHF/3-21G.This reaction is believed to be nonsynchronous but concerted,taking place through a twisted four membered ring transition state.Two types of frontier orbital interactions are involved in this reaction.The activation barrier is calculated to be 123.1KJ/mol (MP2/3-21G result).

Theoretical Study on the Mechanism of the Cycloaddition Reaction between Methylidenesilene and Ethylene

The mechanism of a cycloaddition reaction between singlet methylidenesilene and ethylene has been investigated with MP2/6-31G^＊ and B3LYP/6-31G^＊ methods, including geometry optimization and vibrational analysis for the involved stationary points on the potential energy surface. Energies of the involved conformers were calculated by CCSD（T）//MP2/6-31G＊ and CCSD（T）//B3LYP/6-31 G＊ methods, respectively. The results show that the dominant reaction pathway of the cycloaddition reaction is that a complex intermediate is firstly formed between the two reactants through a barrier-free exothermic reaction of 13.3 kJ/mol, and the complex is then isomefized to a four-membered ring product P2,1 via a transition state TS2.1 with a barrier of 32.0 kJ/mol.

Synthesis and Crystal Structure of α-( N-Protected a mino)β-lactam Derivative of 1 ,5-Benzothiazepine

The crystal of the title compound C, C 30 H 30 N 2O 3S has been prepared by reaction of 1,5 benzothiazepine with N protected glycine and determined by X ray single crystal diffraction. Crystal data: M r =498.62, triclinic with P 1 space group, a=10.880(2), b=13.955(3), c=9.537(2), α=99.34(3)°, β=110.43(3)°, γ=88 56(3)°, V=1338.2(5) 3, F(000)=528, λ (Mo Kα)=0.71073, Z=2, D c =1 237g/cm 3, μ =0.154mm -1 . Final R=0.0453, wR =0.1256 for 3491 observed reflections 〔 I>2σ(I) 〕. Structure analysis reveals that the substituents at C(23) and C(7) in four membered ring are located on the same side. The conformation of seven membered ring is chair like.

Catalytic Formation of Propylene Carbonate from Supercritical Carbon Dioxide/Propylene Oxide Mixture

Propylene carbonate was synthesized from supercritical carbon dioxide (SC-CO2)/ propylene oxide mixture with phthalocyaninatoaluminium chloride (ClAlPc)/ tetrabutylstmmonium bromide (n-Bu4NBr) as catalyst. The high rate of reaction was attributed to rapid diffusion and the high miscibility of propylene oxide in SC-CO2 under employed conditions. Various reaction periods present different formation rate of propylene carbonate, mainly due to the existence of phase change during the reaction. The experimental results demonstrate that SC-CO2 could be used as not only an environmentally benign solvent but also a carbon precursor in synthesis.

Theoretical Study on the Mechanism of the Cycloaddition Reaction between Alkylidene Carbene and Ethylene

The mechanism of cycloaddition reaction between singlet alkylidene carbene and ethylene has been investigated with second-order Moller-Plesset perturbation theory (MP2). By using 6–31G* basis, geometry optimization, vibrational analysis and energetics have been calculated for the involved stationary points on the potential energy surface. The results show that the title reaction has two major competition channels. An energy-rich intermediate (INT) is firstly formed between alkylidene carbene and ethylene through a barrier-free exothermic reaction of 63.62 kJ/mol, and the intermediate then isomerizes to a three-membered ring product (Pl) and a four-membered ring product (P2) via transition state TS1 and TS2, in which energy barriers are 47.00 and 51.02 kl/mol. respectively. PI is the main product.

Activation of Carbon Dioxide and Synthesis of Propylene Carbonate

Cycloaddition of carbon dioxide and propylene oxide to propylene carbonate catalyzed by tetra-tert-butyl metal phthalocyanine in the presence of tributylamine (TBA) shows higher yield than catalyzed by unsubstituted metal phthalocyanine. Comparing different catalysts of diverse metals, (t-Bu)4PcMg is more active than (t-Bu)4PcFe. But (t-Bu)4PcCo and (t-Bu)4PcNi only have low catalytic activities towards the reaction. Moreover, the yield will increase as the temperature increases.