Di-tert-butylbiphenyl Research Articles

Synthesis and Reduction of a Cyclic (Alkyl)(amino)bromoborane to Generate a Thermally Labile Cyclic (Alkyl)(amino)boryl Anion

Abstract A cyclic (alkyl)(amino)bromoborane (CAABBr) was synthesized by a reaction of the corresponding hydroborane with bromine in the presence of triethylamine. Reduction of the resulting CAABBr with Li powder and 4,4′-di-tert-butylbiphenyl (DBB) generated a thermally labile cyclic (alkyl)(amino)boryllithium (CAABLi) which was characterized by NMR spectroscopy. Quenching of the mixture reduced by Li/DBB with methanol-d1 or MeOTf at low temperature gave a deuterioborane or methylborane, supporting the generation of CAABLi.

Chemically Prelithiated Graphene for Anodes of Li-Ion Batteries

To improve the reversible capacity and electrochemical performance of the Li-ion batteries, prelithiation is one of the promising solutions as it leads to the reduction of irreversible capacity and stabilization of electrode surfaces after prelithiation. However, typical electrochemical prelithiation has drawbacks including a longer reaction period and low efficiency of the process. Here, we demonstrate a facile route for the one-pot synthesis of chemically prelithiated graphene before assembling the battery cell. In the reaction of a mixture consisting of graphene oxide (GO), lithium, and 4,4′-di-tert-butylbiphenyl (DTBP), the prelithiation and reduction of GO have occurred simultaneously by the assistance of DTBP. The prelithiated graphene exhibits improved reversible capacity (643 mAh g–1), cyclic stability (capacity retention of 87.4% after 200th cycle), and rate capability compared to those of GO and reduced graphene oxide (RGO). This chemical prelithiation method is expected to enable the efficient production of prelithiated graphene anodes for improving the performance of Li-ion batteries.

Generation, Stability, and Utility of Lithium 4,4′-Di-tert-butylbiphenylide (LiDBB)

Several procedures were evaluated for the preparation of lithium 4,4'-di-tert-butylbiphenylide (LiDBB, Freeman's reagent) from lithium metal and 4,4'-di-tert-butylbiphenyl (DBB) in THF. Solutions with nominal concentration of 0.4 and 1.0 M were formed. The stability of LiDBB solutions was evaluated over time, and the gradual uptake of lithium metal was observed. At 0 °C the LiDBB solutions were stable for over a week in THF. At 20 °C the LiDBB solution underwent various decomposition pathways, which led to uptake of more lithium metal and the accumulation of side products. These decomposition pathways were studied, and the importance of ethene in the destruction of THF by LiDBB was observed. On a practical note, LiDBB solutions in THF were stable and effective for over a week at 0 °C or for more than 37 weeks when stored under argon at -25 °C. These observations will extend the utility of LiDBB as a reagent in organic synthesis.

Synthesis of N-aryl imidazoles catalyzed by copper nanoparticles on nanosized silica-coated maghemite

A magnetically recoverable catalyst consisting of copper nanoparticles (CuNPs) on nanosized silica-coated maghemite is presented. The catalyst has been prepared under mild conditions by mixing the magnetic support with a freshly prepared suspension of CuNPs obtained by fast reduction of anhydrous CuCl2 with lithium sand and a catalytic amount of DTBB (4,4′-di-tert-butylbiphenyl) as electron carrier. This copper-based catalyst has shown to be very efficient in the N-(hetero)arylation of imidazole using (hetero)aryl bromides and iodides as arylating agents under ligand-free conditions. The catalyst is easily recovered by means of an external magnet and can be reutilized in three N-arylation cycles without apparent loss of catalytic activity.

Copper nanoparticles supported on silica coated maghemite as versatile, magnetically recoverable and reusable catalyst for alkyne coupling and cycloaddition reactions

A versatile and magnetically recoverable catalyst consisting of copper nanoparticles on silica coated maghemite nanoparticles (MagSilica®) is presented. The catalyst has been prepared under mild conditions by fast reduction of anhydrous CuCl2 with lithium sand and a catalytic amount of DTBB (4,4’-di-tert-butylbiphenyl) as electron carrier, in the presence of the magnetic support. The catalyst has been fully characterized and its performance in different coupling and cycloaddition reactions of terminal alkynes has been studied. This new copper-based catalyst has shown to be very efficient and easily reusable in the Glaser alkyne dimerization reaction in THF, the multicomponent Huisgen 1,3-dipolar cycloaddition reaction in water and the three-component synthesis of propargylamines under solvent free conditions.

Direct reductive amination of aldehydes using lithium-arene(cat.) as reducing system. A simple one-pot procedure for the synthesis of secondary amines

A simple one-pot procedure for the direct reductive amination of aldehydes using lithium powder and a catalytic amount of 4,4′-di-tert-butylbiphenyl (DTBB) or a polymer supported naphthalene as reducing system is described. The direct reductive amination of a variety of aldehydes with primary amines was achieved simply by adding a mixture of the corresponding carbonyl compound and the amine, over a solution of the lithium arenide in THF at room temperature. For most of the substrates tested the main reaction products were the secondary amines along with variable amounts of the corresponding alcohol and/or imine products. Theoretical DFT calculations have been applied in order to explain the differences in reactivity observed for aromatic substrates.

An effective synthesis of N, N-dimethylamides from carboxylic acids and a new route from N, N-dimethylamides to 1,2-diaryl-1,2-diketones

Carboxylic acids were heated at 150 °C in DMF in the presence of 1.25 equiv of thionyl chloride to give corresponding N, N-dimethylamides in good yields. Tandem chlorination and amidation reactions occurred in the one-pot procedure. Dicarboxylic acids needed prolonged reaction time to produce bisamides in good yields. Some benzamides were efficiently converted into corresponding 1,2-diaryl-1,2-diketones (benzils) under acyloin condensation conditions in the presence of 4,4′-di- tert-butylbiphenyl (DBB) in THF. Ultrasonic irradiation effectively accelerates the reaction, but it is not critical. However, the presence of DBB is fatal to the reaction. Although a few synthetic methods for benzils from benzoic acids have been reported so far, this method is one of the most convenient and highly reproducible procedures.

ChemInform Abstract: Highly Reactive Organolithiums (from “Freeman′s Reagent”) and Their Additions to Naphthalene Oxazolines.

Abstract Generation of organolithium reagents using lithio ditert-butyl biphenyl (Freeman's Reagent) leads to facile additions to the naphthalene oxazolines.

ChemInform Abstract: Reductive Cleavage of 2-Methyleneoxetanes with Lithium and 4,4′-Di-tert-butylbiphenyl.

Abstract 3,3-Dimethyl-2-methylene-4-phenyloxetane (5) undergoes reductive cleavage with lithium and 4,4′-di-tert-butylbiphenyl (DTBB) to give an intermediate dianion, which reacts regioselectively with aldehydes and ketones to give aldol adducts in modest yields. Alternatively, the enolate can be trapped with TMSCl to give the corresponding silyl enol ether.

Nanosized Iron- or Copper-Catalyzed Homocoupling of Aryl, Heteroaryl, Benzyl, and Alkenyl Grignard Reagents

Under very mild reaction conditions, iron or copper nanoparticles efficiently promoted the homocoupling of different Grignard reagents in tetrahydrofuran at room temperature. The nanosized iron or copper particles were generated in situ in a simple and economical way from commercially available FeCl2 or CuCl2, respectively, an excess of lithium powder, and a catalytic amount (5 mol%) of 4,4′-di-tert-butylbiphenyl (DTBB) as electron carrier. The reaction of a series of aryl, heteroaryl, benzyl, and alkenyl Grignard reagents in the presence of a substoichiometric amount of the iron or copper nanoparticles led to the formation of the corresponding homocoupling products in good yield.

Reductive Functionalization of Single-Walled Carbon Nanotubes with Lithium Metal Catalyzed by Electron Carrier Additives

Lithium metal can be used to reduce single-walled carbon nanotubes (SWNT) to carbide-like species under the catalytic effect of di-tert-butyl-biphenyl (DTBP). The resulting nanotube polycarbanions show a significantly increased dispersability THF and react in situ with trimethylchlorosilane, methyl methacrylate, and methyl N-acetamidoacrylate to afford covalently functionalized silyl nanotubes and polymer-wrapped SWNT. The density and average length of the polymer chains attached to the nanotube wall can be widely modified by varying the amount of monomer, lithium, and catalyst.

Modification of styrene polymer with organosilicon groups

AbstractThe homopolymer of 4‐chloromethylstyrene (P1) and its copolymers with styrene (in various mole ratios) were synthesized by bulk and solution free radical polymerizations, respectively, at 70 ± 1°C using α,α′‐azobis(isobutyronitrile) as an initiator. Lithiation of these soluble polymers in THF at −78°C was done and reacted with electrophiles such as tert‐BuMe2Si, Et3Si, and Me3SiCH2 in the presence of 4,4′‐di‐tert‐butylbiphenyl (DTBB) as a catalyst to produce modified polystyrene. In the other way, trimethylsilylmethyl lithium substitute as a nucleophile was covalently linked to the homopolymer and copolymer. The polymers were characterized by IR, 1H NMR, 13C NMR, differential scanning calorimetry (DSC), and gel permeation chromatography. DSC showed that incorporation of silyl substitute in the side chains of homopolymer and copolymers increases the rigidity of the polymers and, subsequently, their glass transition temperature. © 2007 Wiley Periodicals, Inc. Heteroatom Chem 18:414–420, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20314

Regiochemistry in the reductive opening of phthalan derivatives

The lithiation of phthalan derivatives 4, 9 and 12 with an excess of lithium in the presence of a catalytic amount of 4,4′-di- tert-butylbiphenyl (DTBB) in THF at −78 °C gives dianionic intermediates 5, 10 and 13, respectively, which by reaction with different electrophiles [H 2O, t-BuCHO, Me 2CO, (EtO) 2CO] at the same temperature, followed by hydrolysis, leads to regioselective functionalised naphthalenes 7, and biphenyls 11 and 14. The reductive opening takes place with high or total regioselectivity and can be explained considering the electron density in the dianion or in the radical anion, which are formed previous to the carbon–oxygen bond excision. The lithiation of the dihydrofurophthalan derivative 18 with the same reaction mixture but at higher temperature (0 °C) leads to intermediates 19 and 20, resulting from a single and a double reductive cleavage, respectively, which after addition of H 2O and benzaldehyde as electrophiles gives a mixture of compounds 21 and 22.

Active-iron-promoted hydrodehalogenation of organic halides

Under very mild reaction conditions, the active-iron-based reducing system composed of FeCl 2·4H 2O, an excess of lithium powder and a catalytic amount (5 mol%) of 4,4′-di- tert-butylbiphenyl (DTBB) as electron carrier, efficiently performed the hydrodehalogenation of alkyl and aryl halides in tetrahydrofuran at room temperature. The reaction of a series of alkyl and aryl chlorides, bromides, and iodides with this reducing combination led to the formation of the corresponding products resulting from a halogen/hydrogen exchange. Interestingly, the reducing system was efficient in the hydrodehalogenation of aryl fluorides and polychlorinated aromatics. The use of deuterium oxide instead of water in the iron salt allowed the preparation of the corresponding deuterated products. A reaction mechanism has been proposed on the basis of different experiments.

The ammonia-free partial reduction of substituted pyridinium salts

This paper reports a study into the partial reduction of N-alkylpyridinium salts together with subsequent elaboration of the intermediates thus produced. Activation of a pyridinium salt by placing an ester group at C-2, allows the addition of two electrons to give a synthetically versatile enolate intermediate which can be trapped with a variety of electrophiles. Furthermore, the presence of a 4-methoxy substituent on the pyridine nucleus enhances the stability of the enolate reaction products, and hydrolysis in situ gives stable dihydropyridone derivatives in good yields. These versatile compounds are prepared in just three steps from picolinic acid and can be derivatised at any position on the ring, including nitrogen when a p-methoxybenzyl group is used as the N-activating group on the pyridinium salt. This publication describes our exploration of the optimum reducing conditions, the most appropriate N-alkyl protecting group, as well as the best position on the ring for the methoxy group. Electrochemical techniques which mimic the synthetic reducing conditions are utilised and they give clear support for our proposed mechanism of reduction in which there is a stepwise addition of two electrons to the heterocycle, mediated by di-tert-butylbiphenyl (DBB). Moreover, there is a correlation between the viability of reduction of a given heterocycle under synthetic conditions and its electrochemical response; this offers the potential for use of electrochemistry in predicting the outcome of such reactions.

A New Mild Deprotecting Method for O‐Benzylsulfonyl Phenols and Alcohols Based on a DTBB‐Catalyzed Lithiation.

A variety of alcohols and phenols, protected as the corresponding benzylsulfonic esters, were efficiently deprotected by selective reductive cleavage of the sulfur-oxygen bond, using an excess of lithium sand and a catalytic amount (5 mol%) of 4,4'-di-tert-butylbiphenyl (DTBB) as electron carrier, in THF at 0° C. This deprotection system was also efficient at -50 °C and was compatible with a wide range of other functional groups.

Reductive Ring Opening of Dihydrodibenzothiepine and Dihydrodinaphtho‐oxepine and ‐thiepine.

AbstractFor Abstract see ChemInform Abstract in Full Text.

A New Straightforward and Mild Preparation of Nickel(0) Nanoparticles

Abstract Very fine nickel nanoparticles with diameters of 2.5 ± 1.5 nm have been prepared by reduction of anhydrous nickel(II) chloride with lithium powder and a catalytic amount of 4,4′-di-tert-butylbiphenyl (DTBB) in THF at room temperature.

Reductive ring opening of dihydrodibenzothiepine and dihydrodinaphtho-oxepine and -thiepine

The 4,4′di- tert-butylbiphenyl (DTBB)-catalysed lithiation of dihydrodibenzothiepine ( 1 ) at −78 °C for 30 min followed by reaction with a carbonyl compound [ t BuCHO, Ph(CH 2) 2CHO, PhCHO, ( n-C 5H 11) 2CO, (CH 2) 5CO, (CH 2) 7CO, (−)-menthone] at the same temperature leads, after hydrolysis with 3 M hydrochloric acid, to sulphanyl alcohols 2 . If after addition of a carbonyl compound as the first electrophile [Me 2CO, (CH 2) 5CO, (−)-menthone], the resulting dianion of type II is allowed to react at room temperature for 30 min, a second lithiation takes place to give an intermediate of type III , which by reaction with a second electrophile [Me 2CO, Et 2CO, (CH 2) 5CO, ClCO 2Et], yields, after hydrolysis, difunctionalised byphenyls 4 . The cyclisation of the sulphanyl alcohol 2c under acidic conditions yields the eight-membered sulphur containing heterocycle 3 . The lithiation of dihydrodinaphthoheteroepines 7 and 10 with 2.2 equiv of lithium naphthalenide in THF at −78 °C followed by reaction with different electrophiles [H 2O, D 2O, t BuCHO, Me 2CO, Et 2CO, (CH 2) 4CO, (CH 2) 5CO] at the same temperature leads, after hydrolysis, to unsymmetrically 2,2′-disubstituted binaphthyls 9 and 12 , respectively. When the lithiation is performed with an excess of lithium in the presence of a catalytic amount of DTBB (10% molar), a double reductive cleavage takes place to give the dianionic intermediate VII , which by reaction with different electrophiles [H 2O, Me 2CO, Et 2CO, (CH 2) 4CO, (CH 2) 5CO], followed by hydrolysis with water, yields symmetrically 2,2′-disubstituted binaphthyls 8 and 11 . In the case of starting from ( R)- or ( S)-dihydrodinaphthoheteroepines 7 and 10 , these methodologies allow us to prepare enantiomerically pure compounds 8 , 11 and 12 .

Reduction of Alkyl and Vinyl Sulfonates Using the CuCl2×2H2O—Li—DTBB(cat.) System.

AbstractFor Abstract see ChemInform Abstract in Full Text.