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N,N-Dimethyl- and N,N-diisopropyl-1-halo-2-methyl-l-propenylamines are readily available reagents for the mild deoxyhalogenation of alcohols and hydroxyacids. In this study we showed that the reactivity of the reagents can be tuned by varying the size of the alkyl groups on the reagents: the replacement of methyl by isopropyl groups led to a significant increase of reactivity. We then described a unified procedure for all deoxyhalogenations using the readily available α-chloroenamines as reagents with (bromination, iodination) or without (chlorination) an alkaline bromide or iodide. Finally, we showed that deoxyhalogenation reactions of secondary alcohols were highly stereospecific and generally occurred with inversion of configuration.

A protocol for the regioselective cleavage of unsymmetrical alkyl ethers to generate alkyl alcohol and alkyl bromide products is described. A mixture of trihaloboranes triggers this conversion and exhibits improved reactivity profiles (regioselectivity and yield) compared with BBr3 alone. Additionally, this procedure allows the efficient synthesis of (B-Cl) dialkyl boronate esters. There are limited methods to generate acyclic dialkoxyboryl chlorides, and these intermediates constitute important synthons in main-group chemistry.

Non-heme iron based halogenase enzymes promote selective halogenation of the sp3-C-H bond through iron(iv)-oxo-halide active species. During halogenation, competitive hydroxylation can be prevented completely in enzymatic systems. However, synthetic iron(iv)-oxo-halide intermediates often result in a mixture of halogenation and hydroxylation products. In this report, we have developed a new synthetic strategy by employing non-heme iron based complexes for selective sp3-C-H halogenation by overriding hydroxylation. A room temperature stable, iron(iv)-oxo complex, [Fe(2PyN2Q)(O)]2+ was directed for hydrogen atom abstraction (HAA) from aliphatic substrates and the iron(ii)-halide [FeII(2PyN2Q)(X)]+ (X, halogen) was exploited in conjunction to deliver the halogen atom to the ensuing carbon centered radical. Despite iron(iv)-oxo being an effective promoter of hydroxylation of aliphatic substrates, the perfect interplay of HAA and halogen atom transfer in this work leads to the halogenation product selectively by diverting the hydroxylation pathway. Experimental studies outline the mechanistic details of the iron(iv)-oxo mediated halogenation reactions. A kinetic isotope study between PhCH3 and C6D5CD3 showed a value of 13.5 that supports the initial HAA step as the RDS during halogenation. Successful implementation of this new strategy led to the establishment of a functional mimic of non-heme halogenase enzymes with an excellent selectivity for halogenation over hydroxylation. Detailed theoretical studies based on density functional methods reveal how the small difference in the ligand design leads to a large difference in the electronic structure of the [Fe(2PyN2Q)(O)]2+ species. Both experimental and computational studies suggest that the halide rebound process of the cage escaped radical with iron(iii)-halide is energetically favorable compared to iron(iii)-hydroxide and it brings in selective formation of halogenation products over hydroxylation.

The direct selective halogenation of unactivated C(sp3)-H bonds into C-halogen bonds was achieved using a nano Ag/AgCl catalyst at RT under visible light or LED irradiation in the presence of an aqueous solution of NaX/HX as a halide source, in air. The halogenation of hydrocarbons provided mono-halide substituted products with 95% selectivity and yields higher than 90%, with the chlorination of toluene being 81%, far higher than the 40% conversion using dichlorine. Mechanistic studies demonstrated that the reaction is a free radical process using blue light (450-500 nm), with visible light being the most effective light source. Irradiation is proposed to cause AgCl bonding electrons to become excited and electron transfer from chloride ions induces chlorine radical formation which drives the substitution reaction. The reaction provides a potentially valuable method for the direct chlorination of saturated hydrocarbons.

The invention relates to a preparation method of an alkane brominated material. The preparation method comprises the following steps: adding alkane, a bromine-containing compound or elemental bromine,a catalyst and acid into a solvent; adding the solvent into a light-transmission reaction container under air or oxygen atmosphere; sealing; performing stirring reaction under constant pressure and light illumination conditions; then analyzing a nuclear magnetic yield, and performing extraction, drying, filtration, distillation under reduced pressure and column separation to obtain the alkane brominated material. Compared with the prior art, the preparation method disclosed by the invention has the advantages that by using low-cost and safe bromic salt as a bromine source, the air as an oxidizing agent and a nitrogen-containing reagent as the catalyst, reaction is carried out under the conditions of constant temperature and constant pressure, so that energy conservation and economy are realized, and the preparation method is convenient and safe to operate and is environmentally friendly.

Alkyl sp3C-H bonds of cycloalkanes and functional branch/linear alkanes have been successfully brominated with KBr using air or O2 as an oxidant at room temperature to 40 °C. The reactions are carried out in the presence of catalytic NaNO2 in 37% HCl (aq)/solvent under visible light, combining aerobic oxidations and photochemical radical processes. For various alkane substrates, CF3CH2OH, CHCl3, or CH2Cl2 is employed as an organic solvent, respectively, to enhance the efficiency of bromination.

A base-resistant porphyrin metal-organic framework (MOF), namely PCN-602 has been constructed with 12-connected LNi8(OH)4(H2O)2Pz12] (Pz = pyrazolate) cluster and a newly designed Pyrazolate-based porphyrin ligand, 5, 10, 15, 20-tetrakis(4-(pyrazolate-4-yl)-phenyl)porphyrin under the guidance of the reticular synthesis strategy. Besides its robustness in hydroxide solution, PCN-602 also shows excellent stability in aqueous solutions of F-, CO,2-, and PO43- ions. Interestingly, the Mn3+-porphyrinic PCN-602, as a recyclable MOF catalyst, presents high catalytic activity for the C-H bond halogenation reaction in a basic system, significantly outperforming its homogeneous counterpart. For the first time, a porphyrinic MOF was thus used as an efficient catalyst in a basic solution with coordinating anions, to the best of our knowledge.

α-Chloro-, bromo- and iodoenamines, which are readily prepared from the corresponding isobutyramides have been found to be excellent reagents for the transformation of a wide variety of alcohols or carboxylic acids into the corresponding halides. Yields are high and conditions are very mild thus allowing for the presence of sensitive functional groups. The reagents can be easily tuned allowing therefore the selective monohalogenation of polyhydroxylated molecules. The scope and chemoselectivity of the reactions have been studied and reaction mechanisms have been proposed.

Glycerol is produced as a valuable by-product in the transesterification of fatty acids, but it cannot be used directly as a fuel additive. In this study, we developed a systematic conversion for glycerol, which proceeds via synthesizing the key intermediate, 1,2,3-tribromopropane and using the Suzuki coupling reaction to introduce the alkyl group. A series of Pd/SBA-15 catalysts with different wt% of Pd (10%, 15% and 20%) was prepared by a one step sol-gel method. The structure and composition of the catalysts were characterized by X-ray diffraction analysis (XRD), N2 adsorption-desorption isotherms, transmission electron microscopy (TEM) and inductively coupled plasma optical emission spectrometry (ICP-OES). The metallic state of dispersed palladium in SBA-15 is confirmed with X-ray photoelectron spectroscopy (XPS). Pd/SBA-15 with a Pd loading of 20 wt% shows good catalytic activity at 90 °C with methylboronic acid, allowing the complete conversion of 1,2,3-tribromopropane and 64% selectivity of 3-methylpentane. The optimized catalysts were also employed in coupling reactions between various alkylhalides and methylboronic acid, which obtained the desired product with an excellent selectivity. The catalyst can be successfully recycled five times. After the first cycle, we observed a drop in activity with 20% Pd/SBA-15, which was due to the leaching of palladium but in the later cycles, there was no significant decrease in activity.

The photobromination of C-H bonds by using molecular bromine was reinvestigated under microfluidic conditions. The continuous-flow method suppressed the production of dibrominated compounds and effectively produced the desired monobrominated products with high selectivity. Rapid bromination of benzylic substrates containing a photoaffinity azide group was achieved without any decomposition. Go with the (micro)flow: Photobromination of C-H bonds by using molecular bromine under microfluidic conditions has been investigated (see scheme). The continuous-flow method suppressed the production of dibrominated compounds and effectively produced the desired monobrominated compounds with high selectivity. Rapid bromination of benzylic substrates containing a photoaffinity azide group was achieved without any decomposition.

Transformations that selectively functionalize aliphatic C-H bonds hold significant promise to streamline complex molecule synthesis. Despite the potential for site-selective C-H functionalization, few intermolecular processes of preparative value exist. Herein, we report an approach to unactivated, aliphatic C-H bromination using readily available N-bromoamide reagents and visible light. These halogenations proceed in useful chemical yields, with substrate as the limiting reagent. The site selectivities of these radical-mediated C-H functionalizations are comparable (or superior) to the most selective intermolecular C-H functionalizations known. With the broad utility of alkyl bromides as synthetic intermediates, this convenient approach will find general use in chemical synthesis.

Various cycloalkanes and straight-chain alkanes were efficiently brominated with an aqueous HBr-H2O2 system. This oxidative brominating process was promoted by catalysis and irradiation with light. The cycloalkanes were converted to the corresponding bromo-cycloalkanes in moderate yields and the straight-chain alkanes produced dominantly secondary bromides. This simple but effective bromination method of alkanes is characterized by high atom efficiency, inexpensive reagents and the absence of organic waste, which make it a good alternative to the existing method for Ci￡H activation through bromination. A simple, effective, environmentally friendly method was researched for bromination of alkanes in good yield with HBr as the origin of bromine.

A novel halogenating reagent system for direct halogenation of alcohols has been developed. tert-Butyl bromide, chloride and iodide in combination with the ionic liquid [pmIm]Br have been found to convert alcohols into the corresponding bromides, chlorides and iodides under sonication conditions (or heating) in good yields. Although a variety of primary and secondary alcohols participated in this reaction without any difficulty, tertiary alcohols remained inert. Several alcohol derivatives such as OTMS, OTBDMS, OAc, OTS and OTHP are also transformed into the corresponding halides in one-pot fashion by this procedure. A plausible rationale for this transformation is also presented. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005.

The direct functionalisation of alkanes through bromination and iodination has been successfully achieved. The combination of stoichiometric mixtures of elemental halogen and sodium alkoxides leads to the formation of alkyl hypobromites and hypoiodites as reagents. The halogenation occurs without external photostimulation under thermal reaction conditions. Georg Thieme Verlag Stuttgart.

Reaction of alkanes with bromine promoted by unactivated MnO2 gave the corresponding alkylbromides in excellent yield with good chemoselectivity. The MnO2 could be easily recovered and reused.

NaIO4 oxidizes lithium bromide efficiently under acidic conditions to functionalize alkylbenzenes and alkanes and produce the corresponding bromo and acetoxy derivatives in excellent yields. The protocol also demonstrates the direct conversion of cyclohexane into trans-1,2- dibromocyclohexane in moderate yield.

Reaction of dialkyl- or diaryl-trans-(3,4-epoxycyclopentyl)phosphine oxides 2 with the lithium derivative of methyldiphenylphosphine oxide gives a mixture of (±)-t-4- and (±)-c-4-(disubstituted phosphinoyl)-t-2-(diphenylphosphinoylmethyl)-r-1-cyclopentanol derivatives 13a-c and 16a-c, which could be obtained in pure form by separation of the corresponding acetates 14a-c and 17a-c followed by methanolysis. Compounds 13b and 16b were transformed into the corresponding dehydroxy derivatives 19 and 21 through the Barton procedure. Additionally, 16a was transformed into a diastereomeric mixture of carbamates 22 and 23 on reaction with (S)-α-phenylethylisocyanate which could be separated by repeated crystallization. The relative configuration of compounds 13b, 17a, 21 and 22 was established by X-ray diffraction analysis.

The conversion of primary and secondary alcohols to chlorides and bromides using 1,2-bis(diphenylphosphino)ethane (diphos) is described. Use of this reagent in lieu of the typical triphenylphosphine-carbontetrahalide complex provides a facile means of purifying the desired halide from the phosphine-oxide byproduct.

The present invention relates to triazole and imidazole derivatives of formula I and to their pharmaceutically acceptable acid addition salts. These compounds are NMDA receptor subtype blockers and are useful for the treatment of diseases related to the NMDA receptor.

Reactions of 5-(alkoxy)thianthrenium perchlorates (1) with weakly basic nucleophiles Br-, I- and PhS- (X-) in MeCN and DMSO led to SN2 substitution, E2C elimination, and reaction at sulfornium sulfur to extents depending on the structure of the alkoxy group (RO) in 1 and the nucleophile. Three types of reaction occurred with R = cyclopentyl (1a), cyclohexyl (1b), cis- (1c) and trans- 4-methylcyclohexyl (1d) and cycloheptyl (1e), and X- = Br and I-. That is, SN2 reaction gave RX and thianithrene 5-oxide (ThO), E2C reaction gave cycloalkene and ThO and reaction at sulfonium sulfur gave X2, thianthrene (Th) and cycloalkanol (ROH). Earlier work with R = Me (1f) and Et (1g) and X- = I-. Br- had shown that only SN2 reaction occurred. In contrast with reactions of halide ions, reactions of PhS- with 1b-g occurred only at sulfonium sulfur, giving Th, ROH and PhSSPh (DPDS). For comparison with 1, reactions of Ph2S+OMe (2) with I- and PhS- were carried out. Reaction with I- gave only Ph2S=O and Mel (SN2), Reaction with PhS- gave very little PhSMe (SN2) but mainly Ph2S, MeOH, and DPDS from reaction at sulfonium sulfur. The differences in nucleophilic pathways (PhS- vs Br- and I-) in reactions with 1 and 2 are attributed to differences in thiophilicities of the nucleophiles. The thiophilicity of PhS- dominates its reactions with 1 and 2. The direction toward products (Th, ROH and DPDS) in these reactions is compounded by the ease of displacement of alkoxide from 1 and 2 by PhS-, and the ease with which, subsequently, thiophilic PhS- attacks sulfenyl sulfur in the resulting phenylthiosulfonium ion. Copyright

Mono- or polycarboxylic acid esters are prepared by reacting a salt of such carboxylic acid with an organic halocompound, e.g., a (cyclo)alkyl, (cyclo)alkenyl, aryl or aralkyl halide, in an aqueous reaction medium, in the presence of a catalytically effective amount of a phase transfer catalyst, for example an onium salt.

Aprotic organic superacids CBr4 · 2AlBr3, CBr4 · AlBr3, · CCl4 · 2AlBr3, CCl4 · 2AlBr3, and C6F5CF3 · 2AlBr3 efficiently catalyze the bromination of alkanes and cycloalkanes with Br2. Ethane is selectively brominated at 55-65 °C to give mostly 1,2-dibromoethane (stoichiometric reaction). Propane, butane, cyclopentane, cyclohexane, and methyl-cyclopentane react with Br2 at -40 to -20 °C with good selectivity affording monobromides in high yields (catalytic reactions).

The polyhalomethane*2AlBr3 aprotic organic superacids were shown to effectively catalyze low-temperature ionic bromination of (cyclo)alkanes.Ethane readily reacts with Br2 at 55-65 deg C, affording mainly 1,2-dibromoethane.Propane, butane, and C5-C6 cycloalkanes react at -40 - -20 deg C, resulting in monobromides with high yields and good selectivity.

The bromination of saturated hydrocarbons was studied in the GoAggIII system using CBrCl3 and other polyhaloalkanes. This bromination reaction was compared to free radical processes by (i) evaluating the rates of reactions for a series of polyhaloalkanes, by (ii) measuring the selectivity of the different systems towards various saturated hydrocarbons and by (iii) analyzing the product distribution arising from the bromination of cyclohexyl bromide under both the GoAggIII type conditions and from known processes for alkyl radical generation. Some chlorine containing reagents were also examined for C - Cl bond formation in the GoAggIII system. All the experimental findings support a mechanism for the reaction that is different from one involving free radicals. This non-radical pathway is common in all Gif-type systems, as seen in common patterns of selectivity, conditions is in agreement with a non-radical reaction pathway for the Gif-type bromination and chlorination reactions.

Cyclopentadienyl iodide reacts with tetrabutylammonium bromide to afford cyclopentadienyl bromide ca. 10 times as rapidly as cyclopentyl iodide reacts under the same conditions. Cyclopentadienyl bromide reacts with tetrabutylammonium iodide ca. 103 times as rapidly as does cyclopentyl bromide. To check for allylic substitution, 5-iodocyclopentadiene was metallated with potassium hexamethyldisilazide, and the resulting anion was quenched with D2O/CF3CO2D to afford 5-iodo-5-deuteriocyclopentadiene. This could be trapped when kept very cold, but on warming to room temperature it underwent iodine migration that rapidly scrambled the deuterium position. The high reactivity of the cyclopentadienyl halides in substitution under these conditions is in sharp contrast to their low reactivity under solvolytic SN1 conditions. The possible mechanisms and reasons involved are discussed.

A precise comparison has been made between radical bromination of a series of saturated hydrocarbons using BrCCl3 and the bromination of the same series with the same reagent under Gif-type (GoAggIII) conditions. The relative reactivities in the two series are completely different and confirm a difference in mechanism. Experiments with n-butane and with propane have shown that these gases react with the usual Gif selectivity to furnish 2-butanone and acetone respectively.

Aprotic organic superacids with the composition AcBr*2AlX3 (X = Cl, Br) are efficient catalysts (Cat) for the bromination of n-alkanes and cycloalkanes by molecular bromine.Under the given conditions, the reactions afford (predominantly or exclusively) monobromides in high yields.

The reaction of trialkylboranes with bromine is greatly accelerated by base.Bromination in the presence of sodium hydroxide provides alkyl bromide along with a large amount of the corresponding alcohol.The use of sodium methoxide as a base eliminates this undesirable side reaction and provides an improved yield of alkyl bromide.Consequently, hydroboration, followed by bromination in the presence of sodium methoxide, provides a convenient new procedure for the conversion of alkenes into alkyl bromides.The organoboranes, obtained via hydroboration of terminal alkenes, react with the utilization of all three alkyl groups attached to boron, providing nearly quantitative yields of alkyl bromides. This procedure also accommodates common organic functional groups, as demonstrated by the preparation of methyl 11-bromoundecanoate and 11-bromoundecyl acetate from the corresponding functionally substituted alkenes.Under these conditions, secondary and bulky primary alkyl groups react more sluggishly.However, a procedure involving simultaneous addition of bromine and methanolic sodium methoxide provides improved results for such derivatives.Surprisingly, the base-induced bromination of tri-exo-nobornylborane results in an inversion of configuration at the reaction center to give predominantly endo-2-bromonorbornane.A mechanism is proposed to account for this remarkable inversion.

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Alkyldiphenylbismutanes 1 have been synthesized for the first time (61-92 percent).These compounds are air sensitive, not spontaneously inflammable liquids which decompose not below ca. 170 deg C.The diphenylbismutino group is very good equivalent for Cl- or Br-substituents at aliphatic residues since halogenolysis of the Bi-Alk bond with SO2Cl2 or Br2 already occurs at -40 to 0 deg C (corresponding fissions of As-Alk and Sb-Alk bonds afford heating to ca. 130 or ca. 220 deg C).

The complex [(H2O)5Cr-c-C5H9]2+ is formed in the reaction of Cr2+ with H2O2 in aqueous solution saturated with cyclopentane. Reaction of Cr2+ with cyclopentyl radical, a step observed directly by pulse radiolysis (k = (8.0 ± 1.0) × 107 M-1 s-1), yields (H2O)5Cr-c-C5H92+, the radical being formed by abstraction from the hydrocarbon with HO?. The complex was isolated chromatographically and characterized by its absorption spectrum and the products of reactions (C5H9Br from Br2, C5H9OH from homolysis in the presence of Fe3+ and Cu2+). It decomposes by parallel unimolecular pathways of acidolysis (→OOH2+ + c-C5H10, k298 = (4.86 ± 0.12) × 10-4 s-1, ΔH≠ = 73.5 ± 2.4 kJ mol-1, ΔS≠ = -61.5 ± 7.9 J mol-1 K-1 and homolysis (→Cr2+ + ?C5H9, k298 = (1.07 ± 0.16) × 10-4 s-1, ΔH≠ = 126 ± 2.9 kJ mol-1, ΔS≠ = 102.5 ± 9.3 J mol-1 K-1), although the latter is a reversible and thermodynamically unfavorable process, which occurs only in the presence of oxidizing agents. The complex also reacts in bimolecular displacement reactions (SE2 mechanism) with Hg2+ (k298 = 1.08 ± 0.20 M-1 s-1), Br2 (k298 = 1.30 ± 0.19 × 104 M-1 s-1), and I2 (k298 = 8.2 M-1 s-1).

The competitive N-bromosuccinimide (NBS) bromination of cyclopentane vs. cyclohexane was shown to proceed by a mechanism dominated by either a bromine atom chain, a succinimidyl chain, or a mixed chain.The dominance of each of the major chain-carrying processes depends upon the solvents used, to some degree upon the reactivity of the substrate, and upon the additives (molecular bromine or ethylene) used to moderate or enhance one or the other of the chain processes.No evidence was obtained, from studies of the NBS halogenation of the two substrates used, which required the intermediacy of an excited-state succinimidyl radical to explain the reactivities obtained.The observation that β-bromopropionyl isocyanate is produced under all of the reaction conditions precludes the requirement that brominations using the NBS-Br2 reagent proceed exclusively by a radical species whose reactions do not correlate with a ring-opening process.

The reactions of N-bromosuccinimide with a series of radicals have been studied.These reactions fall into two categories, the more reactive radicals producing ?-succinimidyl and the less reactive radicals producing ?-succinimidyl.The threshold for the changeover from one reaction domain to the other occurs with radicals less reactive than secondary alkyls.These results are interpreted with two transition states, an in-line transition state for the more reactive radicals and an out-of-plane transition state for the less reactive radicals. An upper limit of 18 kcal/mol is established for the enthalpy difference, HS? - HS?.Two new methods for generating S? radicals are indicated.

The photochemical reactions of bicyclopentane with bromine, bromotrichloromethane, t-butyl hypochlorite, di-t-butyl peroxide, and N-bromosuccinimide have been investigated.Trichloromethyl, t-butoxyl, and succinimidyl radicals abstract hydrogen from the C4 ring.The expected bicyclopentyl radicals were not detected and if they are discrete intermediates they must rearrange by fission of the C(1)-C(4) bond common to the two rings to form cyclopent-3-enyl radicals.The e.s.r. spectrum of the latter radicals was obtained.Bromine (and chlorine) atoms may abstract hydrogen, but their major pathway involves attack at the bridgehead carbon atoms in an SH2 reaction with fission of the C(1)-C(4) bond to give 3-halogenocyclopentyl radicals.