One-Step Synthesis of Electron-Poor Alkenes from Triphenylphosphine,Acetylenic Esters, 2,2,2-Trichloroethanol,and Ninhydrin

Protonation of the highly reactive 1:1 intermediates, produced in the reaction between triphenylphosphine and dialkyl acetylenedicarboxylates, by 2,2,2-trichloroethanol leads to vinyltriphenylphosphonium salts, which undergo a Michael addition reaction with a conjugate base to produce the corresponding chlorine-containing stabilized phosphorus ylides. An intermolecular Wittig reaction of the chlorine-containing stabilized phosphorus ylides with ninhydrin leads to the corresponding highly electron-poor chlorine-containing alkenes.     

Synthesis of the indene, THF, and pyrrolidine skeletons by Lewis acid mediated cycloaddition of methylenecyclopropanes with aldehydes, N-tosyl aldimines, and acetals

Methylenecyclopropanes (MCPs 1) react with aldehydes, N-tosyl aldimines, and acetals to give the corresponding indene, THF, and pyrrolidine cycloaddition products in the presence of BF3 x OEt2 under mild reaction conditions. Some special transformations of MCPs 1 with aldehydes have been reported in this paper. A plausible reaction mechanism has been discussed, which is based on a deuterium-labeling experiment and the Prins-type reaction mechanism.     

Synthesis of 2, 2, 5, 5-tetramethyltetrahydrothiophene

Under the conditions of the Grignard reaction, 2, 5-dimethyl-2, 5-hexanediol has been obtained from diethyl succinate. Under the action of sulfuric acid, the latter has been cyclized to 2, 2, 5, 5-tetramethyl-tetrahydrofuran which, in its turn, by treatment with phosphorus pentasulfide, has given 2, 2, 5, 5-tetramethyltetrahydrothiophene. Its reaction with methyl iodide has given 2, 2, 5, 5-tetramethyltetrahydrothiophene methiodide.     

A novel MCR of isocyanates, aldehydes, and dienophiles

[reaction: see text] A novel one-pot procedure for the three-component coupling reaction of isocyanates, aldehydes, and dienophiles (IAD reaction) has been developed. Condensation of isocyanates and aldehydes and subsequent Diels-Alder reactions with electron-deficient dienophiles furnishes endo-selective amino-substituted cyclohexenes in good yield.     

Virtual libraries of tetrapyrrole macrocycles. Combinatorics, isomers, product distributions, and data mining

A software program (PorphyrinViLiGe) has been developed to enumerate the type and relative amounts of substituted tetrapyrrole macrocycles in a virtual library formed by one of four different classes of reactions. The classes include (1) 4-fold reaction of n disubstituted heterocycles (e.g., pyrroles or diiminoisoindolines) to form β-substituted porphyrins, β-substituted tetraazaporphyrins, or α- or β-substituted phthalocyanines; (2) combination of m aminoketones and n diones to form m × n pyrroles, which upon 4-fold reaction give β-substituted porphyrins; (3) derivatization of an 8-point tetrapyrrole scaffold with n reagents, and (4) 4-fold reaction of n aldehydes and pyrrole to form meso-substituted porphyrins. The program accommodates variable ratios of reactants, reversible or irreversible reaction (reaction classes 1 and 2), and degenerate modes of formation. Po?lya's theorem (for enumeration of cyclic entities) has also been implemented and provides validation for reaction classes 3 and 4. The output includes the number and identity of distinct reaction-accessible substituent combinations, the number and identity of isomers thereof, and the theoretical mass spectrum. Provisions for data mining enable assessment of the number of products having a chosen pattern of substituents. Examples include derivatization of an octa-substituted phthalocyanine with eight reagents to afford a library of 2,099,728 members (yet only 6435 distinct substituent combinations) and reversible reaction of six distinct disubstituted pyrroles to afford 2649 members (yet only 126 distinct substituent combinations). In general, libraries of substituted tetrapyrrole macrocycles occupy a synthetically accessible region of chemical space that is rich in isomers (>99% or 95% for the two examples, respectively).     

Highly site, regio-, and stereoselective multicomponent reaction of benzimidazole carbenes, isothiocyanates, and allenoates

The novel three-component reaction of benzimidazole carbenes with isothiocyanates and allenoates proceeded efficiently in a highly site, regio-, and stereoselective manner to produce predominantly spiro[benzimidazoline-2,3′-tetrahydrothiophene] derivatives. The reaction was proposed to occur via a tandem nucleophilic addition of carbenes to isothiocyanates followed by an unusual [3+2] cycloaddition to the less activated carbon-carbon double bond of allenoates.     

Ruthenium-catalyzed propargylic substitution reactions of propargylic alcohols with oxygen-, nitrogen-, and phosphorus-centered nucleophiles

The scope and limitations of the ruthenium-catalyzed propargylic substitution reaction of propargylic alcohols with heteroatom-centered nucleophiles are presented. Oxygen-, nitrogen-, and phosphorus-centered nucleophiles such as alcohols, amines, amides, and phosphine oxide are available for this catalytic reaction. Only the thiolate-bridged diruthenium complexes can work as catalysts for this reaction. Results of some stoichiometric and catalytic reactions indicate that the catalytic propargylic substitution reaction proceeds via an allenylidene complex formed in situ, whereby the attack of nucleophiles to the allenylidene C(gamma) atom is a key step. Investigation of the relative rate constants for the reaction of propargylic alcohols with several para-substituted anilines reveals that the attack of anilines on the allenylidene C(gamma) atom is not involved in the rate-determining step and rather the acidity of conjugated anilines of an alkynyl complex, which is formed after the attack of aniline on the C(gamma) atom, is considered to be the most important factor to determine the rate of this catalytic reaction. The key point to promote this catalytic reaction by using the thiolate-bridged diruthenium complexes is considered to be the ease of the ligand exchange step between a vinylidene ligand on the diruthenium complexes and another propargylic alcohol in the catalytic cycle. The reason why only the thiolate-bridged diruthenium complexes promote the ligand exchange step more easily with respect to other monoruthenium complexes in this catalytic reaction should be that one Ru moiety, which is not involved in the allenylidene formation, works as an electron pool or a mobile ligand to another Ru site. The catalytic procedure presented here provides a versatile, direct, and one-step method for propargylic substitution of propargylic alcohols in contrast to the so far well-known stoichiometric and stepwise Nicholas reaction.     

Reactions of 4-ethoxyflavylium, 4-ethoxychromylium,and 4-ethoxyfurochromylium salts with several amines

The reactions of 4-ethoxyflavylium, 4-ethoxychromylium, and 4-ethoxyfurochromylium salts in acidic media with several acids were investigated. In the reaction with hydrazine the furochromylium salt forms pyrazole, whereas both α,β-substituted benzopyrylium salts are converted to azines. The reaction of hydroxylamine with the flavylium salt gives a flavone oxime, whereas the reaction with the furochromylium salt gives an isoxazolylbenzofuranol.     

Density functional computations of the cyclopropanation of ethene catalyzed by iron (II) carbene complexes Cp(CO)(L)FeCHR,L = CO,PMe3, R = Me,OMe, ph,CO2Me

Density functional theory has been used to study the Fe‐catalyzed cyclopropanation of Fe‐carbene complexes with ethene. All the intermediates and transition states were optimized completely at the B3LYP/6‐31+G(d,p) level. Calculation results confirm that the cyclopropanation of Fe‐carbene complexes with ethene involves the two reaction paths I and II . In the reaction path I , the double bond of ethene attacks directly on the carbene carbon of Fe‐carbene complexes to generate the cyclopropane. In the reaction path II , ethene substitution for PMe₃ or CO in the Fe‐carbene complexes leads to the complexes M2 ; and the attack of one carbon of ethene on the carbene carbon results in the complexes M3 with a Fe? C? C? C four‐membered ring, and then generates the cyclopropane via the elimination reaction. For Fe‐carbene complexes A , C , D , E , and H , the main reaction mode is the reaction path I ; for Fe‐carbene complexes B , F , and G , the main reaction mode is the reaction path II . © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2008     

Investigation of condensed pyrimidine,pyrazine, and pyridine systems

The reaction of 5-hydroxy-6-aminopyrimidines with chloromalonic ester in alcohol or with bromomalonic ester in dimethylformamide leads to 6-carbethoxypyrimido-7-oxazinones, whereas a mixture of 6-carbethoxypyrimido-7-oxazinones and 6,6-spirodipyrimido-7-oxazinones is formed in the reaction with bromomalonic ester in alcohol. The latter oxazinones were obtained by reaction of 5-hydroxy-6-aminopyrimidines with dibromomalonic ester. Some of the properties of the synthesized compounds were studied.See [1] for communication XXV.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 391–396, March, 1978.     

Syntheses, characterization, and X-ray crystal structures of beta-diketiminate group 13 hydrides, chlorides, and fluorides

A series of organometallic compounds of group 13 metals supported by the sterically encumbered beta-diketiminate ligand containing hydrides, fluorides, chlorides, and bromide have been synthesized and structurally characterized. The synthetic strategy applied utilizes halide metathesis and reduction of metal chlorides to the corresponding hydrides. Thus, the reaction of LLi.OEt2 with MeMCl2 affords LM(Me)Cl (M = Al (1), Ga (2), In (3)) and LGaBr2 (4) with GaBr3. Reduction of LGa(Me)Cl with LiH.BEt3 leads to the formation of LGa(Me)H (10). Synthesis of LGaH(2) (12) has been accomplished by reacting LGaI2 (8) with LiH.BEt3. LAl(Me)Cl (1) and LAlH2 (6) have been converted to LAl(Me)F (5) and LAlF2 (7), respectively. The former was obtained in a reaction of LAl(Me)Cl with Me3SnF while the latter was isolated in a reaction of LAlH2 with BF3.OEt2. Similarly reaction of LGaI2 (8) with Me3SnF affords LGaF2 (9). Compounds reported herein have been characterized by elemental analyses, IR, NMR, EI-MS, and single-crystal X-ray diffraction techniques.     

Plate, wire, mesh, microsphere, and microtube composed of sodium titanate nanotubes on a titanium metal template

Sodium titanate nanotube/titanium metal composites were synthesized by hydrothermal treatment of titanium metals with various morphologies such as plate, wire, mesh, microsphere, and microtube at 160 degrees C in aqueous NaOH solution and by the subsequent fixation treatment by calcination at 300 degrees C. The surface of the composite was covered with sodium titanate nanotubes with a diameter of approximately 7 nm, and the core part of the composite was titanium metal phase. The raw titanium metal acts as a template or a morphology-directing agent of micrometer size or more to arrange the nanotubes as well as a titanium source for the formation of nanotubes. The concentration of titanium species increases in the reaction solution as the dissolution of titanium metal is accelerated by the reaction between titanium and OH-. Furthermore, with an increase in concentration of titanium species in the reaction solution, the titanium species are re-precipitated as sodium titanate nanotubes onto the titanium metal. Titanium metal with a large surface area and volume can form sodium titanate nanotubes on the surface of the titanium metal, though titanium metal with a small volume and surface area tends to dissolve with the hydrothermal treatment. Even in the synthesis using titanium metal with a small volume and surface area, sodium titanate nanotubes are formed and cover the surface of the titanium metal by adding another titanium metal as a source of titanium species in the reaction solution.     

Tertiary Acetylenic Alcohols,Ethers, and Esters on the Basis of Isocamphanone,Camphor, Fenchone,Isofenchone, and Adamanthanone

Acetylenic lithium alcoholates were synthesized by reactions of 1-hexyne, 1-octyne, and phenylacetylene with butyllithium with subsequent reaction of the resulting acetylides with isocamphanone, (±)-camphor, (+)-fenchone, isofenchone, and adamanthanone. The latter reaction is controlled by steric factors. Lithium alcoholates were used to synthesize the corresponding alcohols, ethers, and esters. Configurational assessment of the products was performed on the basis of quantum-chemical calculations and X-ray diffraction analysis.     

Synthesis of the Indene,THF, and Pyrrolidine Skeletons by Lewis Acid Mediated Cycloaddition of Methylenecyclopropanes with Aldehydes,N‐Tosyl Aldimines,and Acetals

Methylenecyclopropanes (MCPs 1 ) react with aldehydes, N‐tosyl aldimines, and acetals to give the corresponding indene, THF, and pyrrolidine cycloaddition products in the presence of BF₃?OEt₂ under mild reaction conditions. Some special transformations of MCPs 1 with aldehydes have been reported in this paper. A plausible reaction mechanism has been discussed, which is based on a deuterium‐labeling experiment and the Prins‐type reaction mechanism.     

Reduction of nitrates,the no donors,by hemoglobin in the presence of cysteine

Hemoglobin (Hb) reduces 3,3-bis(nitroxymethyl)oxetane (NMO) only in the presence of cysteine (Cys) via intermediate cysteine thionitrate. The kinetics of the reaction of NMO with Cys and the kinetics and mechanism of formation of NO in the ternary system Hb-NMO-Cys were studied. The formation rate of Hb-NO in the ternary system is higher than that of Hb-NO in the reaction of Hb only with NO ₂ ⁻ generated in the binary system NMO-Cys. The second-order rate constants of the main reaction steps in the system Hb-NMO-Cys were estimated by simulating the kinetics of the reactions with a system of equations taking into account equilibria between all components of the reaction mixture. Hemoglobin reduces cysteine thionitrate, the intermediate in the reaction of NMO with Cys, to NO. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 725–731, April, 2007.     

Dual reactivity of diphenylphosphinous and phenylphosphonous acid amides in reactions with N-acetoxymethyl-substituted diethylamine,benzamide, and acetamide

Conclusion N-Acetoxymethyldiethylamine reacts with tetraethyldiamidophenylphosphonite and diethylamidodiphenylphosphinite, and N-acetoxymethylbenzamide with tetraethyldiamidophenylphosphonite at the phosphorus atom only to form Arbuzov reaction products. The reaction of N-acetoxymethylacetamide with tetraethyldiamidophenylphosphonite and diethylamidodiphenylphosphinite, and the reaction of N-acetoxymethylbenzamide with diethylamidodiphenylphosphinite proceed at two reaction centers at the phosphorus atom to form the Arbuzov reaction products, and at the nitrogen atom to form acetoxyphosphinites (phosphonites) and N-diethylaminomethylamides.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, pp. 2765–2769, December, 1986.     

Stability, reactivity, solution, and solid-state structure of halomethylzinc alkoxides.

In this paper, we report our findings regarding the development of a Lewis acid-catalyzed cyclopropanation of allylic alcohols with bis(iodomethyl)zinc. Iodomethylzinc alkoxides can be formed by treatment of an alcohol with bis(iodomethyl)zinc. These species are not prone to undergo cyclopropanation at low temperature but the addition of a Lewis acid in catalytic amounts induces the cyclopropanation reaction. Using this procedure, we demonstrated that the Lewis acid-catalyzed pathway significantly overwhelms the uncatalyzed one. This paper describes fundamental issues regarding the preparation and stability of halomethyl zinc alkoxides in solution as well as their aggregation state in solution and solid-state structures. Furthermore, the competition reaction between the inter- vs intramolecular cyclopropanation will be studied. Finally, we will discuss the possible activation pathways to explain the Lewis acid activation of halomethylzinc alkoxides. These findings provided new insights on the reactivity of ROZnCH(2)I and established the groundwork for the elaboration of an enantioselective version of the reaction.     

阻燃中间体3,9-二氯-2,4,8,10-四氧代-3,9-二磷杂螺[5.5]十一烷的合成

以PCl3和季戊四醇为原料合成了中间体3,9$C二氯-2,4,8,10$C四氧代-3,9-二磷杂螺[5.5]十一烷,产率达99.6%.对反应条件进行了优化,最佳反应条件为:PCl3和季戊四醇摩尔比为2.5∶1,反应温度80℃,反应时间1.5h.     

The Baylis-Hillman reaction: a novel source of attraction, opportunities, and challenges in synthetic chemistry

The Baylis-Hillman reaction is a successful, useful, and atom-economical carbon-carbon bond forming reaction, which has grown from an obscure level to the level of high synthetic popularity due to its operational simplicity and also due to the enormous applications of the Baylis-Hillman adducts in organic synthesis. In this tutorial review, we briefly describe the way this reaction has grown to its present heights and the opportunities, attractions, and challenges the reaction offers with respect to its asymmetric and intramolecular versions, and mechanistic aspects.     

Regioselective trapping of terminal di-, tri-, and tetraynes with benzyl azide

[Structure: see text] The reaction of benzyl azide with terminal di-, tri-, and tetraynes appended with a range of functional groups has been explored. Standard reaction conditions for BnN3 catalyzed by CuSO4.5H2O gave alkynyl, butadiynyl, and hexatriynyl triazoles in moderate to good yields. The reaction proceeds regioselectively as determined by the X-ray crystallographic analysis of three derivatives (1c, 1d, and 3c), and no evidence of multiple azide addition to the polyyne framework is observed.