Synthesis of tertiary α-amino phosphonate by one-pot three-component coupling mediated by LPDE

A very mild, efficient and simple method for the synthesis of tertiary α-amino phosphonates is reported by reaction of an aldehyde, a secondary amine and trialkylphosphite in ethereal solution of lithium perchlorate, LPDE, at ambient temperature with high yields.     

ULTRASOUND ACCELERATED REDUCTIVE COUPLING OF IMINE OR IMINIUM ION GENERATED IN 5 M LITHIUM PERCHLORATE SOLUTION BY LITHIUM METAL

A novel one-pot reductive coupling of imine or iminium ion generated in the concentrated ethereal lithium perchlorate solution was achieved in the presence of lithium metal. The yield of the reaction depends on the reactivity preformed imine or iminium ion. Diamines were formed with high diastereoselectivity in some cases in about 5 h. The reaction time was doubled without the use of ultrasound acceleration.     

Solvent-Free Thiolysis of Epoxides under Lithium Perchlorate Catalysis

Solvent-free ring opening of 1,2-epoxides with thiols using catalytic amounts of lithium perchlorate affords high yields of β-hydroxy sulfides. Nucleophilic attack of the thiols occurs regioselectively at the sterically less hindered side of the epoxides.     

Solvent-Free Thiolysis of Epoxides under Lithium Perchlorate Catalysis

Summary. Solvent-free ring opening of 1,2-epoxides with thiols using catalytic amounts of lithium perchlorate affords high yields of β-hydroxy sulfides. Nucleophilic attack of the thiols occurs regioselectively at the sterically less hindered side of the epoxides.     

Lithium perchlorate-catalyzed regioselective ring-opening of aziridines with potassium thiocyanate

Aziridines react smoothly with potassium thiocyanate in the presence of a catalytic amount of lithium perchlorate in acetonitrile under mild reaction conditions to afford the corresponding β-aminothiocyanates in high yields and with high regioselectivity. The combination of lithium perchlorate and acetonitrile provides a convenient catalytic medium to perform the reactions under neutral conditions.     

Synthesis of chiral vicinal C2 symmetric and unsymmetric bis(sulfonamide) ligands based on trans-1,2-cyclohexanediamine by aminolysis of N-tosylaziridines

The ring opening of N-tosylaziridines with aliphatic amines can be efficiently catalyzed by lithium perchlorate to provide derivatives of the trans-1,2-diamine in high yields. The reaction was used in desymmetrization of several cyclic N-tosylaziridines using chiral amines. Using this strategy, an efficient synthesis of chiral vicinal C₂ symmetric bis(sulfonamide) and unsymmetrical bis(sulfonamide) ligands based on trans-1,2-cyclohexanediamine was developed.     

Solvent effects on the aggregation state of lithium dialkylaminoborohydrides

DFT calculations were performed to determine the effects of ethereal solvents on the aggregation state of lithium dialkylaminoborohydrides (LABs). The calculations included dimerization energies in the gas phase, with continuum solvation only, microsolvation with coordinating ethereal ligands, and a combination of the microsolvation and continuum models. The continuum model alone overestimates the stability of the dimers, apparently due to the lack of steric effects from the coordinating ethereal ligands. The use of the combined microsolvation and continuum solvation models predicts lithium dimethylaminoborohydride to be a mixture of monomer and dimer in THF, and more sterically hindered lithium aminoborohydrides to exist primarily as monomers. The kinetics of amination of 1-chlorodecane by lithium dimethylaminoborohydride showed no detectable change in reaction rate with time, suggesting that the LAB reagent may exist primarily as a monomer in THF.     

Racemic and chiral expanded salen-type complexes derived from biphenol and binaphthol: Salbip and salbin

The reaction of 2-fluoronitrobenzene with 2,2′-biphenol or (R)-binaphthol, followed by reduction and subsequent reaction of the resulting diamine with two equivalents of a salicylaldehyde, affords expanded salen-type ligands having backbones based on biphenol or binaphthol: salbipH₂, (R)-salbinH₂ and (R)-salbin(t-Bu)₄H₂. Deprotonation of these ligands with sodium methoxide or potassium hydride, followed by metallation with M(OAc)₂ (M = Mn, Co, Ni, or Cu), affords the corresponding metal complexes in good yield (61-85%). The species containing Mn, Co, and Ni all have distorted octahedral geometry, as determined by X-ray crystallography. The ethereal oxygen atoms occupy two coordination sites with metal-oxygen distances ranging from 2.19 to 2.36 Å. The imine nitrogen atoms are trans to each other in the solid state, an impossible geometry in traditional salen-type complexes. The species containing Cu are distorted square planar and show much longer metal-ethereal oxygen distances ranging from 2.79 to 3.22 Å. The manganese complexes are competent catalysts for the epoxidation of olefins.     

Lithium perchlorate suspend in methylene chloride, a mild, efficient and reusable catalyst for the synthesis of ferrocene aminonitrile derivatives

A practical and efficient method for the synthesis of α-aminonitriles of ferrocene by one-pot three-component reaction of ferrocenecarboxaldehyde, trimethylsilyl cyanide and amines catalyzed by lithium perchlorate suspend in CH₂Cl₂ is reported under mild and neutral reaction conditions in high yields and short reactions times.     

Lithiated imines: solvent-dependent aggregate structures and mechanisms of alkylation

We describe efforts to understand the structure and reactivity of lithiated cyclohexanone N-cyclohexylimine. The lithioimine affords complex solvent-dependent distributions of monomers, dimers, and trimers in a number of ethereal solvents. Careful selection of solvent provides exclusively monosolvated dimers. Rate studies on the C-alkylations reveal chronic mixtures of monomer- and dimer-based pathways. We explore the factors influencing reactants and alkylation transition structures and the marked differences between lithioimines and isostructural lithium dialkylamides with the aid of density functional theory calculations.     

Expedient synthesis of 3-substituted-1,2,3,6-tetrahydropyridines

The treatment of alkyl or aryl halides with an excess of tetrakis(pyridine)lithium tetrakis(N-dihydropyridyl)aluminate affords the corresponding 3-substituted-1,2,3,6-tetrahydropyridines in moderate to good yields via a tandem alkylation-reduction reaction.     

LiClO4- or LiOTf-accelerated 1,3-dipolar cycloaddition reactions: a facile synthesis of cis-fused chromano[4,3-c]isoxazoles

Acetonitrile solutions of lithium perchlorate or lithium triflate are found to accelerate considerably the intramolecular 1,3-dipolar cycloaddition reactions of nitrones derived in situ from hydroxylamines and the O-prenyl derivatives of salicylaldehydes to afford enhanced rates and improved yields of tetrahydrochromano[4,3-c]isoxazole derivatives with high diastereoselectivity. The stereochemistry of the products has been assigned by using extensive NMR studies.     

One-pot three-step thioconjugate addition-oxidation-Diels-Alder reactions of ethyl propiolate

Ethyl propiolate undergoes one-pot three-step thioconjugate addition-oxidation-Diels-Alder cycloaddition when treated with a variety of thiols in the presence of catalytic base, meta-chloroperbenzoic acid, lithium perchlorate, and cyclopentadiene. The reaction of S-aryl thiols is catalyzed by trialkylamines, and the reaction of aliphatic thiols requires catalytic alkoxide base. Yields of the major diastereomer of the conveniently functionalized bicyclic products range from 47% to 81% depending upon the thiol reactant, which compares favorably to yields observed when the entire synthesis is performed step-by-step.     

Lithium perchlorate-induced electrophilic activation: one-pot synthesis of 3-aryl-2-thioxotetrahydropyrimidin-4-one derivatives from aryl isothiocyanates

A novel methodology for the synthesis of N-substituted-3-aryl-2-thioxotetrahydropyrimidin-4(1H)-one derivatives had been developed by the condensation of aryl isothiocyanates with β-amino esters using lithium perchlorate as a catalyst and triethylamine as a base. This strategy not only overcomes the disadvantages of the reported methods but also provides high yield of the product in short span of time by an easily workable procedure.     

Aminoalkylation with Aldehydes Mediated by Solid Lithium Perchlorate

The solid LiClO₄-mediated one-pot reaction of aldehydes with secondary amines and C nucleophiles afforded the corresponding aminoalkylation products in high yields. Unlike the previous reported procedure, the aminoalkylation of aldehyde was achieved in the presence of only 0.5 equivalents of solid lithium perchlorate in dichloromethane as the solvent with good to high yields at room temperature.     

Aminoalkylation with Aldehydes Mediated by Solid Lithium Perchlorate

Summary. The solid LiClO₄-mediated one-pot reaction of aldehydes with secondary amines and C nucleophiles afforded the corresponding aminoalkylation products in high yields. Unlike the previous reported procedure, the aminoalkylation of aldehyde was achieved in the presence of only 0.5 equivalents of solid lithium perchlorate in dichloromethane as the solvent with good to high yields at room temperature.     

Magnesium perchlorate as an efficient catalyst for the synthesis of imines and phenylhydrazones

Magnesium perchlorate has been found to be an efficient catalyst for the synthesis of imines and phenylhydrazones by the reaction of carbonyl compounds with amines and phenylhydrazine in high yields at room temperatures and in short times. The condensation of less electrophilic carbonyl compounds with poorly nucleophilic amines affords the imines in excellent yields.     

LiClO4-catalyzed highly diastereoselective synthesis of cis-aziridine carboxylates

Aldimines (generated in situ from aldehydes and amines) undergo ready addition with ethyl diazoacetate in the presence of a catalytic amount of lithium perchlorate in acetonitrile to afford the corresponding cis-aziridine carboxylates in high yields with high diastereoselectivity. 10 mol% LiClO₄ in acetonitrile provides a convenient catalytic media to perform the reactions under mild and neutral conditions.     

Synthesis of aminopyridines from 2-fluoropyridine and lithium amides

Lithium amides promote the amination of 2-fluoropyridine under mild reaction conditions, providing 2-aminopyridines in good yields and purity. Treatment of 2-fluoropyridine with 1 equiv of lithium amide at room temperature affords complete conversion after 2 h. To our knowledge, this is the first study of lithium amide-promoted amination of fluoropyridines that are not further activated by electron-withdrawing groups.     

Asymmetric synthesis of pent-3-yl (R)-6-methyl-cyclohex-1-ene carboxylate

An expeditious asymmetric synthesis of pent-3-yl (R)-6-methyl-cyclohex-1-enecarboxylate has been achieved in four steps in 42% overall yield employing as the key step a domino reaction initiated by a highly diastereoselective lithium amide 1,4-conjugate addition to a nona-2,7-diendioic diester followed by a 6-exo-trig cyclisation of the thus formed enolate. Cope elimination protocol of the cyclic adduct affords, depending on the lithium amide used, the corresponding nitro-compound or the expected cyclohexene derivative. The methyl group attached to the cyclohexane ring is achieved by selective ester hydrolysis and subsequent Barton decarboxylation.