Cobalt(II) chloride catalyzed one-pot synthesis of alpha-aminonitriles

A simple and efficient method has been developed for the synthesis of alpha-aminonitriles by a one-pot three- component condensation of aldehydes, amines, and potassium cyanide in acetonitrile in the presence of a catalytic amount of CoCl2 at room temperature.     

Cobalt(II) porphyrazine catalysed reduction of nitrite

Studies on the catalytic reduction of nitrite on carbon electrodes modified with Co(II) tetra-2,3-pyridinoporphyrazine (CoTppa, 1), N,N′,N′′,N′′′-tetramethyltetra-2,3-pyridinoporphyrazine ([CoTm-2,3-tppa]⁴⁺, 2) and Co(II) N,N′,N′′,N′′′-tetramethyltetra-3,4-pyridinoporphyrazine ([CoTm-3,4-tppa]⁴⁺, 3) are reported. There is a close correspondence between the proximity of the methyl groups to the porphyrazine ring and the catalytic activity of the porphyrazine complexes. Bulk electrolysis gave ammonia and hydroxylamine as some of the products. The catalytic activity of the cationic complex, 3, towards the detection of low concentrations of nitrite (<10⁻⁹ M) in water containing sodium sulfate, was compared with the activities of the anionic cobalt(II) tetrasulfophthalocyanine ([CoTSPc]⁴⁻, 4) and the mixed [Co^IITm-3,4-tppa]⁴⁺·[CoTSPc]⁴⁻ (5) complexes. Complex 5 showed the best catalytic activity of the three in that large currents were obtained for very low concentrations of nitrite.     

Gold(III) chloride catalysed synthesis of 5-alkylidene-dihydrothiazoles

A two step synthesis of dihydrothiazoles is presented. First, the previously unknown N-propargylic dithiocarboimidates are produced in good yields from easily available, cheap starting materials. The subsequent gold catalysed ring closure is fast and efficient, leading to dihydrothiazoles through a cascade of 5-exo-dig cyclisation and 1,3-alkyl migration. The yields range from 74% to 95%.     

Ketone synthesis under neutral conditions. Cu(I) diphenylphosphinate-mediated,palladium-catalyzed coupling of thiol esters and organostannanes

[reaction: see text] A versatile approach to ketone synthesis is described. The reaction relies on the palladium-catalyzed, copper diphenylphosphinate-mediated coupling of thiol esters with organostannanes under neutral reaction conditions. This reaction complements the previously described coupling of thiol esters with boronic acids that used dual thiophilic-borophilic activation methodology.     

Cobalt(II) chloride complexes in molten acetamide

The absorption spectra of Co(II) chloride species were studied in molten acetamide containing variable concentration of chloride ligand, in the wavelength range 400–800 nm, at 90°C. The stepwise formation of CoCl_j^(2-j) complexes (J = 1–4) was observed. Addition of chloride ligand (up to 4 molar) dramatically changed Co(II) absorption spectra due to change in co-ordination from octahedral through a severely distorted octahedral to tetrahedral co-ordination. Overall equilibrium constants β_j and consecutive stability constants K_j(j = 1–4) were calculated using SPELMA program for simultaneous computation of equilibrium constants and molar absorption coefficients for each complex species. Distribution of the Co(II) species was also calculated in the studied ligand concentration range.     

Cobalt(II)chloride catalyzed chemoselective thioacetalization of aldehydes

A mild and chemoselective dithioacetalization procedure for the protection of various aldehydes in the presence of catalytic amount of cobalt(II)chloride is described.     

First examples of enantioselective palladium-catalyzed thiocarbonylation of prochiral 1,3-conjugated dienes with thiols and carbon monoxide: efficient synthesis of optically active beta,gamma-unsaturated thiol esters

A catalyst system based on [Pd(OAc)(2)]/(R,R)-DIOP has been found to effect asymmetric thiocarbonylation of certain prochiral 1,3-dienes to produce good yields of optically enriched beta,gamma-unsaturated thiol esters. The reaction was performed under an atmosphere of carbon monoxide (400 psi) at 110 degrees C in methylene chloride for 60 h. The asymmetric thiocarbonylation proceeded with good to excellent enantioselectivities (up to 89% ee). The stereoselectivity is strongly influenced by the structure of the chiral phosphine ligands and substrates, as well as by the reaction conditions. The enantiodetermination step is assumed to be CO insertion to a pi-allylpalladium intermediate.     

Rhodium catalysed addition of boronic acids to anhydrides: a new method for the synthesis of ketones

The efficient transmetalation from boron to rhodium is exploited in a new synthesis of aryl and alkenyl ketones.     

An efficient and facile one-pot synthesis of cyanohydrin esters from carbonyl compounds catalyzed by iron(III) chloride

A variety of cyanohydrin esters were readily prepared from carbonyl compounds with trimethylsilyl cyanide and acid anhydride under the influence of a catalytic amount of iron(III) chloride in a convenient one-pot procedure.     

A new and efficient one-pot synthesis of aromatic alkynyl ketones from aromatic esters

The reaction of aromatic esters with alkynyllithiums in the presence of lithium morpholinide and BF₃·OEt₂ gave aromatic alkynyl ketones in good yield (78-87%).     

Bis(diphosphaferrocene) palladium(II) dimer complexes as efficient catalysts in the synthesis of arylboronic esters

Bis(diphosphaferrocenes)PdCl₂ dimers efficiently catalyse cross-coupling reactions between aryl iodides and pinacol borane in dioxane at 80 °C to afford the corresponding aryl boronic esters derivatives in excellent yields.     

A simple synthesis of thiol esters from copper-I-mercaptides and acyl chlorides

Thiol esters are obtained from acyl chlorides and copper-I-mercaptides in excellent yields.     

Copper(II) chloride as a new,efficient additive suppressing racemization in peptide synthesis by the carbodiimide method

Copper(II) chloride was found to be an extremely efficient additive suppressing racemization in the carbodiimide mediated couplings.     

Solid supported synthesis of phosphinates via palladium (0) catalysed coupling reactions

In order to gain a broad access to phosphinic acid derivatives, a palladium catalysed coupling reaction of aryl iodides with hypophosphorous acid derivatives has been developed on the solid phase. The resulting arylphosphorous acids (or esters) were derivatised using addition reactions with aldehydes, imines and isocyanates, to give phosphinic acids (or esters) with alpha-hydroxy, alpha-amino or aminoacyl groups attached to the aryl phosphorus moiety. This approach provided a broad chemical entry into a class of polar phosphinates compounds which were rather difficult to handle using normal solution phase synthesis. The synthetic potential of this solid phase based methodology was demonstrated by the synthesis of targeted libraries against the enzyme dihydrodipicolinate synthase (DHDPS).     

Cobalt(II) chloride as a novel and efficient catalyst for the synthesis of 1,2,5‐trisubstituted pyrroles under solvent‐free conditions

CoCl₂ is used as an efficient catalyst in the Paal–Knorr condensation of 2,5‐hexadione with primary amines under solvent‐free conditions, leading to the formation of pyrrole derivatives in excellent yield. This method is very easy, rapid, and high yielding reaction for the synthesis N‐substituted pyrrole derivatives. © 2008 Wiley Periodicals, Inc. Heteroatom Chem 19:592–595, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20482     

A new one-pot synthesis of difluoro(organylsulfinyl)acetic acid esters

A novel single-step method for the synthesis of esters of difluoro(organylsulfinyl)acetic acids, by reacting aromatic compounds with isopropyl chlorosulfinyldifluoroacetate, was developed. The feasibility of transforming the sulfoxide intermediates into corresponding sulfides and sulfones was demonstrated.