1,1-Regioselective alkenylboration of styrenes enabled by palladium catalysis

Despite the 1,2-difunctionalization reactions of styrenes have been well developed, the 1,1-regioselective addition reaction remains challenging. We disclose herein a palladium-catalyzed, highly 1,1-regioselective alkenylboration of styrenes by using alkenyl triflates and a diboron reagent as the coupling partners. A wide scope of styrenes derivatives and alkenyl triflates participate this reaction to provide the corresponding allyl boronates with high regioisomeric ratios. The success of this reaction is ascribed to the application of 1,10-phenanthroline-derivated ligand and the addition of ammonium chloride salt. Moreover, acrylate esters can also selectively afford the 1,1-alkenylboration products under the same reaction conditions.     

Synthesis of 1,1′-diacetylferrocene dioxime esters

1,1′-Diacetylferrocene dioxime was synthesized by the reaction of 1,1′-diacetylferrocene with hydroxylamine. The dioxime reacts readily with carboxylic acids chlorides in the presence of pyridine with the formation of 1,1′-diacetylferrocene dioxime esters.     

Experimental study on the reactions of vibrationally excited 1,1-difluorocyclopropane

Vibrationally excited 1,1-difluorocyclopropane, generated by addition of singlet methylene to 1,1-difluoroethene, reacts according to four reaction channels by isomerization as well as by elimination of difluoromethylene. Identification of the products leads to a critical view on an early study dealing with this reaction system. The pressure dependence of the reaction is investigated. The apparent rate-constants of the reaction paths were determined.     

Palladium-catalyzed 1,1-difunctionalization of ethylene

The 1,1-difunctionalization of ethylene, with aryl/vinyl/heteroaryl transmetalating agents and vinyl electrophiles, is reported. The reaction is high-yielding under a low pressure of ethylene, and regioselectivity is generally high for the 1,1-disubstituted product. The process is highlighted by the use of heteroaromatic cross-coupling reagents, which have not been competent reaction partners in previously reported efforts.     

Synthesis of substituted phenols via 1,1-dichloro-2-nitroethene promoted condensation of carbonyl compounds with DMF

A novel and efficient metal-free synthesis of phenolic compounds was developed via coupling cyclization of DMF as a carbon source with active methylene compounds such as 1,3-dicarbonyl compounds with the assistance of 1,1-dichloro-2-nitroethene. The method we used was different from other traditional phenol functionalization methods. In the reaction, the 1,1-dichloro-2-nitroethene as a promoter which unlike our previous research on 1,1-dichloro-2-nitroethene. The method allows the convenient construction of phenolic compounds under mild reaction conditions and moderate yields.     

The Study of Alcoholysis of 1,2-Thiazetidine-l,l-dioxide with Quantum Chemical Method

The alcoholysis mechanism of 1,2-thiazetidine-1,1-dioxide with methanol, in which the relatively stable product is sulfonate ester, has been investigated by quantum chemical method. Our calculations indicate the reaction for alcoholysis of 1,2-thiazetidine-1,1-dioxide proceeds via two possible mechanisms: concerted and stepwise. In the stepwise mechanism, two possible reaction pathways can be followed while only one possible reaction pathway can be followed in the concerted mechanism.     

Synthesis of two Novel 2-Aminocyclopropylidene-1,1-bisphosphonates

The synthesis of tetraethyl aminocyclopropylidene-1,1-bisphosphonate 1 and tetraethyl 2-(aminométhyl)cyclopropylidene-1,1-bisphosphonate 2 are described. The key steps include Michael addition, cyclisation and Curtius reaction for compound 1 and cyclisation, azide nucleophilic substitution and Staudinger reaction for 2.     

The cycloaddition of nitrones with homochiral cyclopropanes

The cycloaddition of nitrones and enantiomerically pure cyclopropane-1,1-dicarboxylates is examined. Transfer of optical activity to the adduct is dictated by thermal reaction conditions and nature of cyclopropane substitution. Optically active 2-substituted cyclopropane-1,1-dicarboxylates are shown to racemize under typical reaction conditions, providing evidence for a zwitterionic ring-opened intermediate.     

从醛无溶剂制备1,1-二乙酸酯的催化剂Cu3/2PMo12O40/SiO2

芳香醛和脂肪醛在温和条件下经乙酸酐和Cu3/2PMo12O40/SiO2催化可转变成 1,1-二乙酸酯. 发现Cu3/2PMo12O40/SiO2是在无溶剂存在下制备 1,1-二乙酸酯的有效催化剂. 使用同一催化剂和乙腈作溶剂可使生成的 1,1-二乙酸酯发生逆反应脱保护生成醛. 这种新的方法具有反应时间短和收率高的优点,而且催化剂重复使用几次不丧失活性.     

2-烯丙基-1,1-偕二金属环己烷的合成研究

在无水乙醚中－１－锂代环已烯和烯丙基溴化镁于为水溴铧锌作用下发生金属化克兰节省理排反应,生成２－烯丙基－１,１－偕二金属环乙烷。通过对温度１溶剂量物凤料顺序等重排反应主要影响因素的考察和优化,可使２－烯丙基－１,１－偕二环已烷的收率达到６５％。     

Ring expansion reactions of 4-amino-1,1-dioxo-[1,2,3,5]-thiatriazoles

An unusual ring-expansion reaction of 4-amino-1,1-dioxo-[1,2,3,5]-thiatriazoles has been identified that produces the relatively rare 5-amino-1,1-dioxo-[1,2,4,6]-thiatriazines and. Initial alkylation of the thiatriazole with alpha-halo-esters at N-3 produces alpha-substituted esters which, under basic reaction conditions, undergo opening of the thiatriazole ring and re-closure to a thiatriazine ring. Similar alkylations of with diethyl chloromalonate and ethyl dichloroacetate lead to the loss of SO2 and the production of triazine and triazole, apparently by an initial alkylation at N-5. The reaction of with phenacyl bromides or a phenacyl dibromide forms fully unsaturated 5-amino-1,1-dioxo-[1,2,4,6]-thiatriazines.     

含有联萘环结构的新型环氧树脂的合成与性能研究

以2-萘酚为原料,先合成出2,2?二羟基-1,1?联萘,再合成出一种新型的具有联萘结构的环氧树脂(BEBN)。通过红外光谱研究了树脂的结构,推测了树脂合成的机理,并对树脂的性能作了一定的研究。该树脂的固化物表现出良好的热性能及力学性能。     

Efficient synthesis of highly functionalized cyclic aminimides

[reaction: see text]. Simple condensation reactions of various alpha,beta-epoxy or alpha,beta-aziridinyl methyl esters with 1,1-dialkyl hydrazines provided cyclic aminimides (1,1-dialkyl-3-oxopyrazolidines) with a heteroatom substituent at the 4-position in good yields. The reaction proceeds smoothly, without any coreagent, providing the product as an easily isolable precipitate. The reaction is expected to be a good candidate for combinatorial synthesis of a highly functionalized five-membered ring scaffold. The scope and limitations of this reaction were investigated by varying the substituents R(1)-R(5).     

Syntheses of dibenzo[c,e][1,2]diselenin and related novel chalcogenide heterocyclic compounds

Reaction of 2,2′-dilithio-1,1′-binaphthyl with selenium followed by air oxidation gives a mixture of dinaph-thoselenophene and dimer and oligomers of 2,2′-diseleno-1,1′-binaphthyl. 2,2′-Dilithio-1,1′-biphenyl reacts with selenium to afford dibenzo[c,e][1,2]diselenin. Structures of the dimeric 2,2′-diseleno-1,1′-binaphthyl and dibenzo[c,e][1,2]diselenin have been confirmed by X-ray crystallographic analyses. Similar reaction of 2,2′-dilithio-1,1′-binaphthyl with sulfur or tellurium gives a mixture of dinaphthothiophene and dinaphtho[2,1-c:-1′,2′-e][1,2]dithiin or a mixture of dinaphthotellurophene and oligomer of 2,2′-ditelluro-1,1′-binaphthyl, respectively. Dibenzotellurophene and oligomer of 2,2′-ditelluro-1,1′-biphenyl are obtained from reaction of 2,2′-dilithio-1,1′-biphenyl with tellurium.     

Synthesis of 1,1-diarylethylenes from an α-stannyl β-silylstyrene

The synthesis of a family of 1,1-diarylethylenes from an α-stannyl β-silylstyrene through a combination of a Stille coupling and a protodesilylation reaction is described. This approach avoids the problematic cine-substitution, which is a well documented side reaction during the palladium-assisted elaboration of α-substituted vinylstannanes to 1,1-disubstituted ethylenes.     

Synthesis of 1,3-diynes via palladium-catalyzed reaction of 1, 1-dibromo-1-alkenes

[reaction: see text] Both symmetric and unsymmetric 1,3-diynes were prepared from the palladium-catalyzed reaction of 1,1-dibromo-1-alkenes. The formation of symmetric 1,3-diynes 2 (homocoupling) was catalyzed by a weak ligand, tris(2-furyl)phosphine (TFP), and the addition of catalytic amount of CuI accelerated the reaction. The synthesis of unsymmetric 1,3-diynes 4 (the Sonogashira reaction) required a highly electron rich tris(4-methoxyphenyl)phosphine as the ligand, and CuI promotes the formation of byproduct 1,1-diynyl-1-alkenes 5.     

A New Route to the Synthesis of Alpha-Alkyltetrahydrothiophene-1,1-Dioxide Compounds

Alpha-alkyltetrahydrothiophene-1,1-dioxide compounds have been prepared in relatively high yield through the reaction of 2-lithiotetrahydrothiophene-1,1-dioxide with primary alkyl halides.     

Novel lactonization of ethenetricarboxylate derivatives: intermolecular trapping of alkenes

A novel cyclization of 1,1-diethyl 2-tert-butyl ethenetricarboxylate (1a) in the presence of a Lewis acid afforded a 5,5-dimethyl-gamma-lactone derivative 2a. The reaction process has been shown to arise from formation by trapping of isobutylene generated in situ. Lewis acid-promoted intermolecular reactions of 1,1-diethyl 2-hydrogen ethenetricarboxylate (5) and various alkenes to afford highly functionalized gamma-lactones were also developed. [reaction: see text]     

Theoretical study on the lithium-halogen exchange reaction of 1,1-dihaloalkenes with methyllithium and the nucleophilic substitution reaction of the resulting alpha-halo alkenyllithiums

Transition structures for the lithium-bromine exchange reaction of 1,1-dibromoalkenes with methyllithium have been located by both the B3LYP and the MP2 levels of theory with the 6-31+G basis set. The reaction with methyllithium dimer gave similar results with lower activation energies. These calculations predict both the kinetic and the thermodynamic stereoselectivity correctly. That is, the sterically more constrained bromine atom of 1,1-dibromoalkenes was predominantly reacted with alkyllithium (dimer) in the kinetic condition. The intramolecular substitution reaction of 4,4-dibromo-3-methyl-3-pentenol in the presence of methyllithium has been investigated. After deprotonation of the alcohol and the lithium-bromine exchange reaction, the intramolecular substitution reaction occurs to give dihydrofuran in a concerted manner. The intermolecular substitution of alpha-chloro alkenyllithium with methyllithium was also studied for comparison. The formation of the indene derivative from 3-(o-bromophenyl)-1,1-dibromo-1-propene in the presence of methyllithium occurs in a similar manner. The lithium-bromine exchange reaction of bromobenzene with methyllithium occurs in an S(N)2 mechanism and the solvent plays an important role.     

Role of the polymer backbone on the reactivity of polymer-supported (dichloroiodo)benzene

-Chlorination of iodinated crosslinked polystyrene with Cl₂ gave polyaryliododichloride containing 1.1 mmol of active chlorine per gram of resin, whilefluorination of the same iodinated resin with XeF₂ gave polyaryliododifluoride, containing 1.05 mmol of active fluorine per gram of resin. Both resins reacted with 1,1-diphenylethylene, reaction withpolyaryliododifluoride giving rearranged 1,1-difluoro-1,2-diphenylethane, while polyaryliododichloride gave 1,2-dichloro-1,1-diphenylethane and 1,1-diphenyl 2-chloroethene. The stereochemistry of chlorine addition with polyaryliododichloride to cis or trans-1-phenylpropene is very similar to that observed in the reaction with Cl₂ under ionic conditions, and its reactivity differs markedly from (dichloroiodo)benzene, which reacts via radical intermediates. Similar studies with 1-phenylalkynes and norbornene are described.