Activated Zinc Dust Research Articles

Multicomponent consecutive Barbier propargylation and CuAAC click reactions using Zn/CuFe2O4 reagent: Entry to anti-fungal triazole compounds

In this article an effort has been made to highlight the utility of copper-based magnetically separable nanocatalyst in combination with activated zinc dust towards environment friendly and efficient one pot synthesis of a variety of novel β-hydroxy 1,4-disubstituted 1,2,3-triazole derivatives in high yield. In addition to its simplicity and milder reaction conditions, this method has the ability to tolerate a wide variety of substitutions in the components. Among the synthesized β-hydroxy 1,4-disubstituted 1,2,3-triazoles,1-Phenyl-2-(1-p-tolyl-1H- [1,2,3]triazol-4-yl)-ethanol (P8) and 1-Phenyl-2-(1-phenyl-1H- [1,2,3]triazol-4-yl)-ethanol (P1) exhibited good antifungal activity.

Selective Synthesis of Trifluoromethyl β‐Lactams by a Zn‐Promoted 2‐Bromo Ester Addition on C‐CF3‐Substituted Aldimines

Starting from C‐CF3‐substituted aldimines, trifluoromethyl β‐lactams were obtained as only products in the reaction with some α‐bromo esters in the presence of activated zinc dust. Different solvents, molar ratios, and temperature were tested to determine the best reaction conditions that led only to desired cyclic compounds. The influence of another ester group on the aldimine chain and the reaction diastereoselectivity were also considered.

Titanocene(III) chloride mediated formal synthesis of magnofargesin and 7′-epimagnofargesin

Formal synthesis of two bioactive lignans, magnofargesin and 7′-epimagnofargesin has been accomplished in both racemic and optically active forms through titanocene(III) chloride (Cp2TiCl) mediated radical induced cyclization reaction. Ti(III) species was generated in situ from the commercially available titanocene dichloride (Cp2TiCl2) and activated zinc dust in dry THF.

Hydantoin-Free Synthesis of Peptide Ester Isocyanates, Isothiocyanates, and Dipeptidyl Ureas: The Application of Zinc Dust in a Carbonylation Procedure without Base

Non-Schotten-Baumann conditions are described for the hydantoin-free synthesis of peptide ester isocyanates using activated zinc dust as a non-basic HCl scavenger. Also, the procedure gives no N-acylated products in the case of the conversion of amino acid and peptide amides into isocyanates.

The stereoselective synthesis of ( Z)-HFC [dbnd]CFZnI and stereospecific preparation of ( E)-1,2-difluorostyrenes from ( Z)-HFC [dbnd]CFZnI via an unusual Pd(PPh 3) 4–Cu(I)Br co-catalysis approach or ( Z)-HFC [dbnd]CFSnBu 3

( Z)-HFC CFZnI was stereoselectively synthesized from activated zinc dust and ( Z)-HFC CFI that was synthesized from chlorotrifluoroethene in a sequential manner. Compared to ( E)-HFC CFZnI, ( Z)-HFC CFZnI was more challenging to prepare in terms of sluggish metallation and formation of by-products, and underwent slower and incomplete Negishi coupling with aryl iodides. In a modification of Negishi coupling, ( E)-α,β-difluorostyrenes were stereospecifically prepared in good to excellent yields under mild conditions from aryl iodides and ( Z)-HFC CFZnI with the co-catalysis of Pd(PPh 3) 4/Cu(I)Br. Experimental investigation and mechanistic rationalization suggested that Cu(I)Br would be a scavenger of free ligands for the facilitation of Pd(PPh 3) 2 formation, and a supplier of ligand for the metathesis process. Alternatively, ( Z)-HFC CFSnBu 3 and aryl iodides with an electron-withdrawing group underwent Stille–Liebiskind coupling to afford ( E)-α,β-difluorostyrenes.

A Practical Approach for the Preparation of Regioregular Poly(3-hexylthiophene)

Scheme 1. Preparation of monomer Polythiophenes have been intensively studied over the last three decades. And major studies have been focused on poly 3-alkylthiophene especially poly 3-hexylthiophene (P3HT), which has shown very unique properties in conducting polymer applications. Of these, the most notable property is electrical conductivity, which is contributed to the delocalization of πelectrons through overlap of π-orbitals. In addition to this, since it is very soluble in normal organic solvents, a good processability has been observed. In general, preparation of P3HT could be achieved by either chemical or electrochemical method. For electrochemical polymerization including FeCl3 catalyzed polymerization, a potential was applied to a solution containing monomer and electrolyte. Chemical synthesis was performed by metal-mediated polymerization of monohalogenated and/or dihalogenated thiophene derivatives under appropriate conditions. An advantage in chemical polymerization over electrochemical method is that this method generally affords a highly regioregular polymer in excellent yields. Since regioregularity of P3HT is a critical element for the application of this polymer, a lot of different procedures have been developed especially in chemical synthetic methods. Generally accepted methods include metal (Ni) catalyzed self-condensation of thienyl organozinc and thienyl Grignard reagents. A big breakthrough for the preparation of regioregular P3HT has been reported by Rieke and McCullough, separately. From these works, high regioregular (> 98%) head-to-tail P3HT has been achieved with reasonable molecular weight. As mentioned above, 2,5-dibromo-3-alkylthiophenes have been extensively used as a monomer in the chemical synthetic method. However, only a few examples of using 2-bromo-5iodo-3-alkylthiopenes have been appeared in the chemical method. Recently, Knochel and co-workers introduced the application of commercially available and relative cheap zinc powder to organic synthesis. This work prompted us immediately to study the possibility of using zinc powder in the preparation of P3HT. To this end, 2-bromo-5-iodo-3-alkylthiopene could be the most proper candidate since zinc dust showed excellent insertion reactivity to carbon-iodine bond. Here, we wish to report the first result obtained from the application of the activated zinc dust to the preparation of regioregular P3HT.

Activated Zinc Dust

Activated Zinc Dust

Titanocene(III) mediated radical cyclizations of epoxides for the synthesis of medium-sized cyclic ethers

Titanocene(III) chloride (Cp 2TiCl) mediated 7- exo and 8- endo radical cyclizations of epoxides towards the synthesis of 7- and 8-membered cyclic ethers have been described. Titanocene(III) chloride was prepared in situ from commercially available titanocene dichloride (Cp 2TiCl 2) and activated zinc dust in THF.

Titanocene(III) chloride mediated radical-induced one-pot synthesis of α-methylene-γ-butyrolactones

A simple and efficient methodology has been developed for the one-pot preparation of α-methylene-γ-butyrolactones by free-radical induced Barbier-type reaction of methyl 2-(bromomethyl)acrylate and aldehydes followed by in situ lactonization. The radical initiator titanocene(III) chloride (Cp 2TiCl) was easily generated in situ from commercially available Cp 2TiCl 2 and activated zinc dust in THF. Ketones remained unaffected under the reaction conditions.

Efficient Synthesis of Aryl Hydroxylactams by Reducing Imides with Activated Zinc Dust.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Efficient Synthesis of Aryl Hydroxylactams by Reducing Imides With Activated Zinc Dust

A series of aryl hydroxylactams (2a, 2b, 2d–2g, 2i–2k, 2m, and 2n) was synthesized by partially reducing aryl cyclic imides in moderate to excellent yields with activated zinc dust alone in acetic acid. This method was regiospecific and can be employed as an alternative for reported methods to partially reduce aryl cyclic imides.

Titanocene(III) mediated 8- endo radical cyclizations for the synthesis of eight-membered cyclic ethers

Titanocene(III) chloride (Cp 2TiCl) mediated 8- endo radical cyclizations towards the synthesis of eight-membered cyclic ethers have been described. Titanocene(III) chloride was prepared in situ from commercially available titanocene dichloride (Cp 2TiCl 2) and activated zinc dust in THF.

Free radical-promoted conjugate addition of activated bromo compounds using titanocene(III) chloride as the radical initiator

Free radical-promoted conjugate addition of activated bromo compounds to α,β-unsaturated ketones and reactive α,β-unsaturated esters has been described using titanocene(III) chloride (Cp 2TiCl) as the radical initiator. Cp 2TiCl was prepared in situ from commercially available Cp 2TiCl 2 and activated zinc dust in THF.

Selective Removal of 2,2,2-Trichloroethyl- and 2,2,2-Trichloroethoxycarbonyl Protecting Groups with Zn?N-Methylimidazole in the Presence of Reducible and Acid-Sensitive Functionalities.

Activated zinc dust in the presence of N-methylimidazole in ethyl acetate or acetone at reflux or room temperature removes 2,2,2-trichloroethyl- and 2,2,2-trichloroethoxycarbonyl protecting groups while azido-, nitro-, chloro-, phenacyl-, and tert-butyl ester functionalities as well as double bonds remain intact.

Concise Enantioselective Synthesis of Furan Lignans (-)-Dihydrosesamin and (-)-Acuminatin and Furofuran Lignans (-)-Sesamin and (-)-Methyl Piperitol by Radical Cyclization of Epoxides

Enantioselective syntheses of furan lignans (-)-dihydrosesamin and (-)-acuminatin and furofuran lignans (-)-sesamin and (-)-methyl piperitol were achieved in up to only three steps in 43%, 42%, 63%, and 60% overall yield,respectively, with high optical purity through stereoselective intramolecular radical cyclization of suitably substituted epoxy olefinic ethers using bis(cyclopentadienyl)titanium(III) chloride as the radical initiator. The key intermediate, chiral epoxy alcohol 4, was prepared by the Sharpless kinetic resolution method. The titanium(III) initiator was prepared in situ from commercially available titanocene dichloride and activated zinc dust in tetrahydrofuran.

Selective removal of 2,2,2-trichloroethyl- and 2,2,2-trichloroethoxycarbonyl protecting groups with Zn– N-methylimidazole in the presence of reducible and acid-sensitive functionalities

Activated zinc dust in the presence of N-methylimidazole in ethyl acetate or acetone at reflux or room temperature removes 2,2,2-trichloroethyl- and 2,2,2-trichloroethoxycarbonyl protecting groups while azido-, nitro-, chloro-, phenacyl-, and tert-butyl ester functionalities as well as double bonds remain intact.

A novel, mild, and facile method to prepare 6-methylidene penem derivatives.

A novel and mild method was established to synthesize 6-methylidene penem compounds. This method entails a MgBr(2)/Et(3)N-promoted aldol-type condensation on 6-bromopenem 12 with an appropriately substituted aldehyde to yield the intermediate acetylated bromohydrin, which was smoothly converted to the final product with simultaneous deprotection of C3 carboxylic acid ester using activated zinc dust and phosphate buffer at pH 6.5. This process provides a useful variation of C-C bond formation method for penem derivatives and also serves as a practical synthetic method to prepare 6-exomethylenepenem derivatives without racemization at the C5 position.

Short and Stereoselective Total Synthesis of Furano Lignans (.+‐.)‐Dihydrosesamin, (.+‐.)‐Lariciresinol Dimethyl Ether, (.+‐.)‐Acuminatin Methyl Ether, (.+‐.)‐Sanshodiol Methyl Ether, (.+‐.)‐Lariciresinol, (.+‐.)‐Acuminatin, and (.+‐.)‐Lariciresinol Monomethyl Ether and Furofuran Lignans (.+‐.)‐Sesamin, (.+‐.)‐Eudesmin, (.+‐.)‐Piperitol Methyl Ether, (.+‐.)‐Pinoresinol, (.+‐.)‐Piperitol, and (.+‐.)‐Pinoresinol Monomethyl Ether by Radical Cyclization of Epoxides Using a Transition‐Metal Radical Source.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Short and stereoselective total synthesis of furano lignans (+/-)-dihydrosesamin, (+/-)-lariciresinol dimethyl ether, (+/-)-acuminatin methyl ether, (+/-)-sanshodiol methyl ether, (+/-)-lariciresinol, (+/-)-acuminatin, and (+/-)-lariciresinol monomethyl ether and furofuran lignans (+/-)-sesamin, (+/-)-eudesmin, (+/-)-piperitol methyl ether, (+/-)-pinoresinol, (+/-)-piperitol, and (+/-)-pinoresinol monomethyl ether by radical cyclization of epoxides using a transition-metal radical source.

Intramolecular radical cyclization of suitably substituted epoxy ethers 4a-g using bis(cyclopentadienyl)titanium(III) chloride as the radical source resulted in trisubstituted tetrahydrofurano lignans and 2,6-diaryl-3,7-dioxabicyclo[3.3.0]octane lignans depending on the reaction conditions. The titanium(III) species was prepared in situ from commercially available titanocene dichloride and activated zinc dust in THF. Upon radical cyclization followed by acidic workup, epoxy olefinic ethers 4a-g afforded furano lignans dihydrosesamin 1a, lariciresinol dimethyl ether 1b, acuminatin methyl ether 1e, and sanshodiol methyl ether 1g directly and lariciresinol 1h, acuminatin 1i, and lariciresinol monomethyl ether 1j after removal of the benzyl protecting group by controlled hydrogenolysis of the corresponding cyclized products. The furofuran lignans sesamin 2a, eudesmin 2b, and piperitol methyl ether 2e were also prepared directly by using the same precursors 4a-f on radical cyclization followed by treatment with iodine and pinoresinol 2h, piperitol 2i, and pinoresinol monomethyl ether 2j after controlled hydrogenolysis of the benzyl protecting group of the corresponding cyclized products. Two naturally occurring acyclic lignans, secoisolariciresinol 5h and secoisolariciresinol dimethyl ether 5b, have also been prepared by exhaustive hydrogenolysis of 2h and 2b, respectively.

Indenylidene complexes of ruthenium: optimized synthesis, structure elucidation, and performance as catalysts for olefin metathesis--application to the synthesis of the ADE-ring system of nakadomarin A.

An optimized and large scale adaptable synthesis of the ruthenium phenylindenylidene complex 3 is described which employs commercially available diphenyl propargyl alcohol 5 as a stable and convenient carbene source. Previous ambiguities as to the actual structure of the complex have been ruled out by a full analysis of its NMR spectra. A series of applications to ring closing metathesis (RCM) reactions shows that complex 3 is as good as or even superior to the classical Grubbs carbene 1 in terms of yield, reaction rate, and tolerance towards polar functional groups. Complex 3 turns out to be the catalyst of choice for the synthesis of the enantiopure core segment 77 of the marine alkaloid nakadomarin A 60 comprising the ADE rings of this target. Together with a series of other examples, this particular application illustrates that catalyst 3 is particularly well suited for the cyclization of medium-sized rings by RCM. Other key steps en route to nakadomarin A are a highly selective intramolecular Michael addition setting the quaternary center at the juncture of the A and D rings and a Takai-Nozaki olefination of aldehyde 73 with CH2I2, Ti(OiPr)4 and activated zinc dust.