Phenylselenenyl chloride as a reagent for the facile preparation of cyclic ethers from diolefins

Various cyclic ethers are prepared in good to excellent yields by treating diolefins with phenylselenyl chloride in aqueous acetonitrile. This is the most facile method for organoselenium-induced formation of cyclic ethers from diolefins so far reported.     

A convenient preparative method for cyclic triphosphenium bromide and chloride salts

Analytically pure chloride and bromide salts of two different cyclic triphosphenium cations are prepared by the reaction of PX3 (X=Cl, Br) in the presence of the halogen-scavenging reagent cyclohexene. For the brominated species, the neutral, volatile 1,2-dibromocyclohexane byproduct is readily removed under reduced pressure, and the desired salts are obtained in high yield. Reactions involving phosphorus trichloride are complicated by the formation of salts containing both chloride and hydrogen dichloride anions. Reactivity experiments on potential undesired halogenated diphosphine byproducts suggest that the formation of such species can be prevented by increasing the concentration of cyclohexene employed in the reaction.     

Gold- and silver-catalyzed highly regioselective addition of active methylenes to dienes, triene, and cyclic enol ethers

The combination of gold and silver salts catalyzed the addition of active methylenes to dienes, triene, and cyclic enol ethers with high regioselectivity. The catalysis provides a synthetically useful method for functionalized carbocycles and heterocycles through a highly atom-economical carbon-carbon bond formation. [reaction: see text]     

Facile preparation and reactivity of bifunctional ionic liquid-supported hypervalent iodine reagent: a convenient recyclable reagent for catalytic oxidation

Novel, efficient, and recyclable bifunctional catalysts bearing ionic liquid supported (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO) and iodoarene moieties were developed and used for environmentally benign catalytic oxidation of alcohols. The reactions using peracetic acid as a green and practical co-oxidant afforded the corresponding carbonyl compounds in high yields under mild conditions and convenient work-up. Furthermore, these ionic liquid supported bifunctional catalysts could be simply recovered and reused.     

New methods and reagents in organic synthesis. 62 trimethylsilyldiazomethane: A convenient reagent for the preparation of acylsilanes

The lithium salt of trimethylsilyldiazomethane smoothly reacts with alkyl halides to give α-trimethylsilyldiazoalkanes which are easily oxidized with m-chloroperbenzoic acid (m-CPBA), giving the corresponding acylsilanes (α-ketosilanes) in good yields.     

Cobalt complex in a room temperature ionic liquid: A convenient recyclable reagent for catalytic epoxidation of cyclic alkenes

Co-catalyzed epoxidation of cyclic alkenes proceeds in ionic liquid media (1-ethyl-3-methylimidazolium hexafluorophosphate). Epoxidation of the alkenes to respective epoxides was greatly accelerated by the use of a cobalt-based catalyst in the presence of H₂O₂ as an oxidant. The catalyst in ionic liquid [Emim]PF₆ was recycled and reused for about seven times.     

Platinum-catalyzed intramolecular hydroalkoxylation of gamma- and delta-hydroxy olefins to form cyclic ethers

Reaction of 2,2-diphenyl-4-penten-1-ol with a catalytic mixture of [PtCl2(H2C=CH2)]2 (1 mol %) and P(4-C6H4CF3)3 (2 mol %) at 70 degrees C for 24 h led to the isolation of 2-methyl-4,4-diphenyltetrahydrofuran in 78% yield. The platinum-catalyzed hydroalkoxylation of gamma-hydroxy olefins tolerated substitution at the alpha, beta, and gamma-carbon atoms and at the internal and cis and trans terminal olefinic positions. Platinum-catalyzed hydroalkoxylation tolerated a number of functional groups including pivaloate and acetate esters, amides, silyl and benzyl ethers, and pendant hydroxyl and olefinic groups. Pt-catalyzed olefin hydroalkylation was also applicable to the formation of fused- and spirobicyclic ethers and was effective for the hydroalkoxylation of delta-hydroxy olefins to form tetrahydropyran derivatives.     

A simple and convenient method for the preparation of diborane from tetrabutylammonium borohydride and benzyl chloride for application in organic synthesis

Diborane is readily generated in situ at 25 °C in toluene using the Bu₄NBH₄/PhCH₂Cl and Bu₄NBH₄/I₂ reagent systems. The reagent prepared in this way is used for the reduction of carbonyl compounds and hydroboration-oxidation of olefins to obtain the corresponding alcohols in good yields.     

Dialkyl aluminium chloride: a reagent for removal of trityl group from trityl ethers of deoxynucleosides,deoxynucleotides, and oligodeoxynucleotides

Detritylation of N-acyl-5′-o-tritylated deoxynucleosides, deoxynucleotides, and oligodeoxynucleotides have been quantitatively achieved in minutes at room temperature by using diethylaluminium chloride or diisobutylaluminium chloride. Reactions take place in unpolar solvents in homogeneous phase under completely aprotic conditions.     

Immobilized porcine liver esterase: a convenient reagent for the preparation of chiral building blocks.

A simple method for the effective, covalent, immobilization of porcine liver esterase ( PLE ) is described, and the application of this reagent for the preparation of chiral building blocks on a 50 – 500 mmol scale is demonstrated.     

Reactions of pyridyl and quinolyl sulfoxides with grignard reagent: A convenient preparation of pyridyl and quinolyl grignard reagents

3-,4-Pyridyl and 4-quinolyl Grignard reagents were generated by the reaction of the corresponding phenyl sulfoxides with PhMgBr and give the adducts upon treatment with various aldehydes and ketones. The stereochemistry for the reaction was investigated.     

A convenient procedure for the synthesis of allyl and benzyl ethers from alcohols and phenols

Allyl and benzyl ethers of alcohols can be prepared conveniently and in high yield with allyl and benzyl bromide in the presence of solid potassium hydroxide without use of any solvent. Phenols can be converted to allyl ethers but are inert to benzylation under above conditions.     

Phenylsulfenyl chloride/N,N-diisopropylethylamine: A useful reagent for cyclic ether formation (sulfenyletherification)

A general method for the formation of cyclic ethers and lactones is described. The procedure employs phenylsulfenyl chloride and N,N-diisopropylethylamine to generate an episulfonium ion intermediate from which the cyclic products arise by internal nucleophilic displacement.     

Facile preparation and reactivity of polystyrene-supported (dichloroiodo)benzene: a convenient recyclable reagent for chlorination and oxidation

A facile one-pot preparation of polystyrene-supported (dichloroiodo)benzene (loading of -ICl₂ up to 1.35 mmol/g) from polystyrene, iodine, and bleach has been developed. This recyclable reagent is useful for efficient chlorination of organic substrates and selective oxidation of various alcohols to the corresponding carbonyl compounds in high yields under mild conditions. The final products are conveniently separated from the polymeric byproduct by simple filtration and isolated in good purity after evaporation of solvent.     

Bismesitylmagnesium: a thermally stable and non-nucleophilic carbon-centred base reagent for the efficient preparation of silyl enol ethers

Bismesitylmagnesium has been established as an accessible, practical, convenient, and non-nucleophilic carbon-centred base reagent for efficient access to silyl enol ethers from a series of ketone substrates at readily utilisable temperatures.     

Regio- and stereoselective synthesis of aziridino epoxides from cyclic dienes

Two different routes for the regio- and stereoselective synthesis of aziridino epoxides from cyclic dienes have been explored. The first strategy involves regiospecific aziridination of cyclic diene derivatives and subsequent epoxidation with m-CPBA to yield cis-aziridino epoxides as major products. The second strategy utilizes regiospecific epoxidation of cyclic diene derivatives followed by Sharpless aziridination to provide exclusively trans-aziridino epoxides. Synthesis of both enantiomers of cis-aziridino epoxides from (R)-(-)- and (S)-(+)-carvones are also reported.     

A new reagent pair sodium percarbonateacetic anhydride for epoxidation of olefins

A new convenient method for epoxidation of olefins by sodium percarbonate — acetic anhydride is reported. It is found that the epoxides in 60–80% yields can be obtained in 18–24 h without ultrasonication. However, higher yields (some nearly quantitative) can be reached only within 1–3 h under ultrasonication. A comparison between the ultrasonicated epoxidations by use of sodium percarbonate and sodium perborate is also made. The experimental results have revealed that ultrasonication plays a main role in accelerating the interaction of both sodium percarbonate and sodium perborate with acetic anhydride, but it does not alter the mechanism of these two epoxidations.