Dichlorocarbene Research Articles

Synthesis and trapping of spiro [bicyclo[4.2.0]octa-2,3-diene-7,2'-[1,3]dioxolane

Spiro[bicyclo[3.2.0]hept-2-ene-6,2'-[1,3]dioxolane] was synthesized by the reaction of bicyclo[3.2.0]hept-2-en-6-one with ethylene glycol in yield of 92%. Addition of dichlorocarbene to Spiro[bicyclo[3.2.0]hept-2-ene-6,2'-[1,3]dioxolane] gave the 3',3'-Dichlorospiro[1,3-dioxolane-2,7'-tricyclo[4.2.0.02,4]octane] in 50 % yields. Finally, the 3',3'-Dichlorospiro[1,3-dioxolane-2,7'-tricyclo[4.2.0.02,4]octane] was submitted to Doering-Moore-Skatebol reaction for the synthesis of allene precursors. The reaction of the 3',3'-Dichlorospiro[1,3-dioxolane-2,7'-tricyclo[4.2.0.02,4] octane] with methyl lithium (MeLi) in the presence of 1,3-diphenylisobenzofuran (DBI) as a trapping reagent under a nitrogen atmosphere at ca. 0 ℃ was started and continued at room temperature for four hours, resulting in the formation of four cyclo adduct isomers of spiro[bicyclo[4.2.0]octa-2,3-diene-7,2'-[1,3]dioxolane].

Gram-Scale Robust Synthesis of 1-Chloro-2,3-dimethyl-4-phenylnaphthalene: A Promising Scaffold with Three Contiguous Reaction Positions

AbstractA three-step reaction sequence for the gram-scale synthesis of 1-chloro-2,3-dimethyl-4-phenylnaphthalene was developed. (i) Stereoselective dichlorocarbene addition to methyl angelate afforded methyl (1S*,3S*)-2,2-dichloro-1,3-dimethylcyclopropane-1-carboxylate (78% yield, >98% purity, distillation). (ii) Addition reaction of two molar amounts of PhLi afforded (1S*,3S*)-2,2-dichloro-1,3-dimethylcyclopropyldiphenylmethanol (81% yield, >98% purity, recrystallization). (iii) Key SnCl4-mediated benzannulation produced the desired product (83% yield, >98% purity, recrystallization) with three contiguous reaction sites. Five derivatization examples including benzylic reactions and cross-couplings at the pendant Cl-position are demonstrated. Some relevant distinctive benzannulations are also discussed.

Stereochemistry of Dichlorocarbene Addition to Alkenes: A Collaborative, Discovery-Based Experiment for the Organic Chemistry Laboratory

A multifaceted experiment, accessible to students either in an introductory organic chemistry course or in a more advanced laboratory setting, is described for investigating the addition of dichlorocarbene to E- and Z-β-methylstyrenes. The innovative exercise, which integrates elements of synthesis, mechanisms, instrumental analysis, computational chemistry, and collaboration, provides students with an opportunity to learn important laboratory skills while highlighting key concepts covered in class. In particular, the coupling constants from 1H NMR spectroscopy are used to diagnose the stereochemistry of addition, and integral ratios are evaluated to determine percent conversion of the starting alkenes into dichlorocyclopropanes. The experimental observations are correlated with results from calculations of the singlet–triplet energy gap in the carbene.

Hydrophobically modified chitin/halloysite nanotubes composite sponges for high efficiency oil-water separation.

A high-performance oil-water separation device that built by environment-friendly materials is a promising strategy to solve water pollution problem. In this study, we developed an oil-water separation system with chitin/halloysite nanotubes (C/HNTs) composites. C/HNTs were crosslinked by epichlorohydrin and freeze-dried, then a porous sponge was formed. The C/HNTs sponge was modified to be hydrophobic via immersing into bromohexadecane ethanol solution. The surface structure, mechanical properties, microstructure, oil absorption and oil-water separation ability of the C/HNTs sponge were investigated. The addition of HNTs significantly increased the compressive strength of chitin sponge without influence on porous structure. IR spectra indicated the successful coating of bromohexadecane on the C/HNTs sponge surface, which enabled the hydrophobicity and lipophilicity of this construct. The inside construct of the C/HNTs sponges were full of interconnected pores, and the pore size ranged from 250 to 500 μm. The absorption capability for various oil and grease were measured, including methylbenzene, sunflower seed oil, carbon dichloride, n-hexane, chloroform and acetone. It is found that the total amount of chloroform absorbed by a C/HNTs sponge was ~11.23 times of the sponge's weight, and the absorption for hexane was ~3.94 times of the sponge's weight. The sponge also exhibited an excellent oil-water separation ability with as high as 98.7% separation efficiency. All the results suggested that the chitin/HNTs sponges with improved mechanical property would have a great potential in oil-water separation.

Investigation of quality and pollution characteristics of groundwater in the Hutuo River Alluvial Plain, North China Plain

Groundwater plays a critical role in northern China, accounting for 62 % of the total water supply in the Beijing–Tianjin–Tangshan region. Groundwater is particularly important in the North China Plain—the largest alluvial plain and one of the most densely populated regions of East Asia. The Hutuo River Plain, which is located in the western portion of the North China Plain, is essential in supplying groundwater to the entire central region of the plain. Groundwater in this region is the main source of industrial, agricultural, and drinking water and therefore directly influences daily life. In this study, 482 groundwater samples including 390 shallow groundwater samples and 92 deep groundwater samples were collected and analyzed to investigate water quality and the effects of anthropogenic activities in the Hutuo River Plain. Application of the improved fuzzy mathematics evaluation method revealed that 21.5 % of the samples exceeded the Class III water standard, and that these samples were primarily in areas containing high concentrations of industrial activity or sewage discharge, and at the same time the native hydrogeological environment is the major factor influencing distribution of most pollution components, groundwater quality in the top of the Hutuo River alluvial–proluvial fan was not very good just as the Vadose zone lithology is a little more coarse, in the leading edge of the alluvial-proluvial fan the vadose zone is mainly formed of clay with very low vertical permeability, these characteristics endow the area with good protective performance, which makes it difficult for surface pollutants to enter the aquifer. Groundwater quality in the region was primarily affected by inorganic materials including total hardness, iron, manganese, total dissolved solids, and nitrate nitrogen, the rates of exceed Class III water standard was 26.45, 17.72, 11.11, 10.58, and 8.47 %, respectively, in shallow groundwater, and 20.20, 16.34, 16.35, 14.43, 2.52 %, respectively, in deep groundwater. There are several organic materials with high detection rates including chloroform, carbon tetrachloride, carbon dichloride, and ortho-dichlorobenzene, the detection rate was 14.02, 2.12, 3.44, 2.48 %, respectively, in shallow groundwater, and there were little organic compounds detected in deep groundwater. Overall, the results indicated that the hydrogeological environment and anthropogenic activities have led to the introduction of toxic metals, nitrogen, and organic materials into groundwater in the Hutuo River Plain. These findings will be useful to future studies of the region and will facilitate the remediation and prevention of contamination in the area.

Synthesis and characterization of new multi-site phase transfer catalyst and its catalytic efficiency in dichlorocarbene addition to (R)-Carvone

A new multi-site phase transfer catalyst (MPTC) was synthesized from 1,4-dibromo-2,3,5,6-tetramethylbenzene that contain 12 active sites per molecule. The MPTC was thoroughly characterized by different spectral techniques, viz., FT-IR, NMR, MALDI-TOF Mass spectroscopic techniques and elemental analysis. The catalytic efficiency was demonstrated by dichlorocarbene addition to (R)-carvone. The MPTC's catalytic efficiency was compared with the commercially available, single site, phase transfer catalysts (PTCs) by monitoring the disappearance of (R)-carvone using gas chromatography. Among these PTCs the newly synthesized MPTC shows higher activity than the four-site, six-site, and commercially available single site PTCs. Further, new MPTC catalyst was selected for thorough kinetic study for the dichlorocarbene addition to (R)-carvone. Furthermore, the experimental parameters such as concentrations of substrate, catalyst, NaOH, stirring speed, and temperature has been found to play a significant role in the reaction rate. Based on the obtained results suitable mechanism was proposed.

Covalent Carbene Functionalization of Graphene: Toward Chemical Band-Gap Manipulation.

In this work, we employ dibromocarbene (DBC) radicals to covalently functionalize solution exfoliated graphene via the formation of dibromocyclopropyl adducts. This is achieved using a basic aqueous/organic biphasic reaction mixture to decompose the DBC precursor, bromoform, in conjunction with a phase-transfer catalyst to facilitate ylide formation and carbene migration to graphene substrates. DBC-functionalized graphene (DBC-graphene) was characterized using a range of spectroscopic and analytical techniques to confirm the covalent nature of functionalization. Modified optical and electronic properties of DBC-graphene were investigated using UV-vis spectroscopy, analysis of electrical I-V transport properties, and noncontact terahertz time-domain spectroscopy. The implications of carbene functionalization of graphene are considered in the context of scalable radical functionalization methodologies for bulk-scale graphene processing and controlled band-gap manipulation of graphene.

The regio- and stereoselective addition of dibromocarbene and dichlorocarbene onto β-himachalene

In this work we used DFT B3LYP/6-31G (d) to study the mechanism, the regio- and stereoselectivity of the [1+2] cycloaddition reaction between β-himachalene and dihalogenocarbene. Analysis of the reactivity indices and calculation of the activation energies of the transition states showed that this reaction is stereoselectives, the treatment of β-himachalene with one equivalent of dibromocarbene leads via an exothermic reaction to the formation of a single product P 1 resulting from the attack of the most substituted double bond C 6 =C 7 of β-himachalene. Treatment of product P 1 with one equivalent of dichlorocarbene leads, again via an exothermic reaction, to formation of the two products P 3 and P 4 , but dibromocarbene does not react with the product P 1 due to the high activation energy of this reaction.

Dichlorocarbene Addition of N-Vinylimidazole under Ultrasound Assisted a New Multi-Site Phase-Transfer Catalyst - A Kinetic Study

The kinetics for dichlorocyclopropanation of N-vinylimidazole with an excess of chloroform has been studied under multi-site phase-transfer catalyst and ultrasound irradiation conditions using aqueous sodium hydroxide as the base. The reaction was carried out at 40°C and a pseudo-first order rate is used to describe the reaction rate at high alkaline concentration (>30 wt.%). Kinetics of the reaction including the effects of the reaction conditions on the conversion of N-vinylimidazole was investigated. A rational explanation was made for a peculiar phenomenon that the conversion of N-vinylimidazole was increased and then decreased with an increase in the amount of sodium hydroxide and the kapp value increases with increasing other kinetic parameters that is the amount of multi-site phase-transfer catalyst, viz., N,N’-dihexyl-4,4’-bipyridinium dibromide, concentration of substrate, ultrasonication, stirring speed, temperature, etc.

Dibromocarbene Functionalization of Boron Nitride Nanosheets: Toward Band Gap Manipulation and Nanocomposite Applications

We report the covalent functionalization of exfoliated boron nitride nanosheets (BNNSs) using dibromocarbene (DBC) species. The functionalization of BNNSs is enabled as the nanosheets are utilized as two-dimensional phase-transfer catalysts for the migration of carbenes across the organic–aqueous phase boundary. We postulate that BNNSs stabilize carbenes by forming B-CBr2 ylides and in turn act as the reaction substrate. DBC functionalization of BNNSs results in the formation of B–C and B–N bonds to the sp2-hybridized BNNS lattice via the formation of dibromo-bridged bicyclo BCN systems. The covalent functionalization was characterized using HR-TEM, AFM, EELS, XRD, EDX, ToF-SIMS, TGA, Raman, XPS, FTIR, and UV–vis techniques. Utilization of CBr2 groups as a means by which BNNSs may be integrated and interfaced with solvents, molecular species, and condensed-phase materials was demonstrated by grafting alkyl chains from the functional groups via alkyl/halogen exchange. Alkyl-functionalized BNNSs were integr...

The Synthesis of 3-Phosphabicyclo[3.1.0]- hexane 3-Oxides and 1,2-Dihydrophosphinine 1-Oxides with Lipophilic P-Alkoxy Substituents by Ring Enlargement

A series of 1-alkoxy-3-phospholene 1-oxides available from the microwave-assisted direct esterification of 1-hydroxy-3-phospholene oxide was converted to the two diastereomers of 6,6-dichloro-3-phosphabicyclo[3.1.0]hexane 3-oxides by the addition of dichlorocarbene to the double bond. Thermolysis of the 3-phospholene oxide–dichlorocarbene adducts afforded the corresponding 1,2-dihydrophosphinine 1-oxides as a ca. 3:1 mixture of two double bond isomers. Relative stability of the isomers of the intermediates and the products and their stereostructures were evaluated by B3LYP/6-31G(d,p) calculations.

Kinetic Study of the CCl2Radical Recombination Reaction by Laser-Induced Fluorescence Technique

Fil: Gomez, Nicolas Damian. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Instituto de Investigaciones Cientificas y Tecnicas para la Defensa. Centro de Investigacion en Laseres y Aplicaciones; Argentina

Two-Dimensional Carbon Compounds Derived from Graphyne with Chemical Properties Superior to Those of Graphene

Computational studies considering both thermodynamic and kinetic aspects revealed that graphyne, a carbon material that has recently been of increasing interest, favours unprecedented homogeneous “in-plane” addition reactions. The addition of dichlorocarbene to the C(sp)-C(sp) bond, a site with outstanding regioselectivity in graphyne, proceeds via a stepwise mechanism. Due to their homogeneous nature, additions occurring at C(sp)-C(sp) bonds yield structurally ordered two-dimensional carbon compounds (2DCCs). 2DCCs have electronic band structures near the Fermi level that are similar to those of graphene and are either electrically semi-conductive or metallic depending on whether the reactions break the hexagonal symmetry. Notably, 2DCCs can be further functionalised through substitution reactions with little damage to the extended π-electron conjugation system. These results suggest that 2DCCs derived from graphyne have physical properties comparable to those of graphene and chemical properties superior to those of graphene. Therefore, 2DCCs are expected to be better suited to practical applications.

Study of addition of difluorocarbene on double bond of triterpenes

In this work, we describe synthesis and characterization of novel triterpenic derivatives formed by the addition of difluorocarbene on activated double bonds of natural and semisynthetic triterpenes. Despite the general trend that introducing hydrophobicity into the triterpenic molecule often causes decrease in cytotoxic activity, there are examples in literature where addition of dichlorocarbene to a terpenic double bond had the opposite effect. That sparked our interest to synthesize similar analogues from our active triterpenes. The reaction only worked with limited amount of substrates and the cytotoxicity of resulting products was very low. We obtained several interesting structures and the major problem was to accurately determine their structures, especially the configuration at newly introduced chiral carbon atoms. For that, we used 2D-NMR methods combined with molecular modeling and one structure was also confirmed by X-ray crystallography.

A Theoretical Study on the Electronic and Electrical Properties of the Single-Walled Carbon Nanotubes with Dichlorocarbene Addition

Electronic and electrical properties of several single-walled carbon nanotubes as well as their derived structures with multi-dichlorocarbene addition are investigated by using self-consistent field crystal orbital method based on density functional theory. The addition can convert metallic tubes into semiconducting ones and increase their carrier mobilities, which are comparable with those of the pristine semiconducting tube. With small amount of dichlorocarbenes, the mobility of semiconducting single-walled carbon nanotube does not decrease. The dichlorocarbene addition can be a good pathway for processing high mobility electronic devices for mixtures of semiconducting and metallic single-walled carbon nanotubes.

Diameter Effect on the Sidewall Functionalization of Single‐Walled Carbon Nanotubes by Addition of Dichlorocarbene

AbstractDichlorocarbene is added to the sidewalls of single‐walled carbon nanotubes (SWNTs) with diameters ranging from 1.2 to 2.2 nm. Small diameter SWNTs are found to react much more easily than large diameter SWNTs. Upon functionalization, the conductance could be largely preserved for almost all SWNTs, while an effective bandgap increase for functionalized metallic SWNTs (m‐SWNTs) and a bandgap reduction for functionalized semiconducting SWNTs (s‐SWNTs) are generally observed. The results suggest that [2 + 1] cycloaddition is an excellent choice of processing, resulting in SWNTs over a large diameter range with electronic properties that are almost unaffected. Furthermore, possible separation of SWNTs according to their diameters could be achieved due to the apparent diameter‐dependent reactivity.

Kinetic study of dichlorocarbene addition to olefins via a quaternized highly branched polyacrylamide as a new multi-site phase transfer catalyst

A quaternized highly branched polyacrylamide was synthesized and used as an efficient multi-site polymeric phase transfer catalyst in dichlorocyclopropanation reaction. The quaternized highly branched polyacrylamide was synthesized via two steps. First, a highly branched polyacrylamide was synthesized via self-condensing vinyl polymerization using appropriate molar ratio of monomer to diperiodatocuprate(III) solution. In the second step, 3-acrylamidopropyltrimethylammonium iodide was polymerized on peripheral area of the highly branched polyacrylamide in the presence of diperiodatocuprate(III) solution. The thermal behavior of highly branched polyacrylamide and that of the quaternized highly branched polyacrylamide was studied by DSC and TGA analyses. Then the activity of the synthesized quaternized highly branched polyacrylamide was investigated as phase transfer catalyst in dichlorocyclopropanation of olefins in biphasic medium. To this purpose, the synthesized catalyst was used in generating dichlorocarbene from chloroform in aqueous sodium hydroxide solution which was subsequently added to olefins. This catalyst is very active and its application yields high volume of products which are obtained in relatively short time. Various factors which influence the rate of dichlorocyclopropanation reaction, such as base concentration, stirring speed, temperature and amount of catalyst, are studied and a mechanism for addition reaction of dichlorocarbene to olefins is proposed. This efficient phase transfer catalyst was reused several times without any loss of activity.

New soluble multi-site phase transfer catalysts and their catalysis for dichlorocarbene addition to citronellal assisted by ultrasound—A kinetic study

Two new soluble multi-site phase transfer catalysts (MPTCs), viz., 1,4-bis-(triethylmethylene ammonium chloride)-2,5-dimethyl benzene (BTMACD) containing di-site and 1,4-bis((3,5-bis(triethylmethyleneammonium chloride)phenoxy)methyl)benzene (TEMACPB) containing tetra-site were prepared and proved by FT-IR, 1H NMR, 13C NMR, mass and elemental analysis. The enhancement of CN peak intensity at 1179cm−1 noticed in FT-IR, the agreement of m/z values, viz., 405 and 888 for di-site and tetra-site respectively with their theoretical values and the percentage of C, H, N elements noticed in elemental analysis has strongly supported the presence of di-site and tetra-site in the BTMACD and TEMACPB catalysts. Further, the presence of number of active-sites in each catalyst was again confirmed by determining their pseudo-first order rate constant for dichlorocarbene addition to citronellal in the presence of ultrasonic irradiation/mechanical stirring. The comparative study reveals that the kobs determined with the combination of ultrasound and mechanical stirring has shown more activity (3 fold) than with their individual effect. Further, the detailed kinetic study performed with superior tetra-site MPTC (TEMACPB) reveals that the kobs are dependent with the stirring speed, [substrate], [catalyst], [NaOH] and temperature. Based on the kinetic results, thermodynamic parameters are evaluated and an interfacial mechanism is proposed.

Effect of Silica on Uncompatibilized and Compatibilized Styrene Butadiene Rubber and Nitrile Rubber Blends

The present paper investigates the interaction of silica filler in uncompatibilized and compatibilized styrene butadiene rubber/nitrile rubber (SBR/NBR) blends of varying compositions. The use of a dynamic mechanical analyzer as a tool for confirming the compatibility by the addition of dichlorocarbene modified styrene butadiene rubber (DCSBR) in these blends has been described. The addition of silica in uncompatibilized as well as compatibilized blends has been found to be increasing the rheometric-processing characteristics such as maximum viscosity and rate of cure. The magnitude of these values has been found to be higher for compatibilized blends and for 50/50 composition. The optimum cure time has been found to be decreasing with silica loading regardless of the presence of the compatibilizer. The magnitude of optimum cure time has been found to be higher for uncompatibilized system and for the composition with higher SBR content. Enhancement in mechanical properties with the addition of silica has been observed for compatibilized blends, more intensely than uncompatibilized samples. A good correlation between mechanical properties and solvent sorption behavior has also been observed.

Dynamic control of dichlorocarbene addition to cyclopropene

The addition of dichlorocarbene to cyclopropene has been studied with direct dynamics quasiclassical trajectories using B3LYP/6‐31G*. The trajectories yielded 1,1‐dichlorobicyclo[1.1.0]butane and 1,1‐dichloro‐1,3‐butadiene in a ratio of 4.7:1, which is consistent with the experimental ratio of 4:1. The large majority of trajectories formed products within 100 fs of the start of the trajectory and proceeded in a concerted manner to the bicyclobutane or butadiene; no zwitterion or biradical intermediate was observed. Eight trajectories generated bicyclobutane and subsequently dissociated chloride to form an ion pair, which recombined to form 2,3‐dichlorocyclobutene. The lifetime of the ion pair averaged 95 fs, which was too short to be considered an intermediate, consistent with previous calculations that characterized the ion pair as a transition state. This study lends strong support to the previous proposition that the addition of CCl2 to cyclopropene is controlled by dynamic effects. Copyright © 2011 John Wiley & Sons, Ltd.