Hypervalent Iodine(III)-Induced Domino Oxidative Cyclization for the Synthesis of Cyclopenta[b]furans.

A new strategy for cyclopenta[]furan synthesis mediated by hypervalent iodine(III) has been described. The approach employs diacetoxyiodobenzene-induced initial dehydrogenation to a putative trienone intermediate and triggered sequential cycloisomerization to form the cyclo-penta[]furan targets.

Stereoselective preparation of conjugated (Z)-1,3-enynes by dehydration reactions of allenic bromohydrins and the use of the enynes in base-mediated tandem allylation ene-carbocyclization reactions with β-ketoesters.

A procedure has been developed for the concise, stereoselective synthesis of (Z)-5-bromo-4-aryl-pent-3-en-1-ynes through Sc(OTf) catalyzed dehydration reactions of allenic bromohydrins. (Z)-1,3-Enynes are transformed to methylenecyclopentenes when subjected to a sequential, one-pot process involving base mediated allylation reactions with ethyl acetoacetate followed by ene-carbocyclization reactions. An unprecedented rearrangement reaction involving 1,5-acyl migration takes place when the methylenecyclopentenes are treated with acid to form highly substituted cyclopentadienes.

Synthesis of 2-Alkenyl-2H-indazoles from 2-(2-Carbonylmethyl)-2H-indazoles.

A procedure has been developed for synthesis of 2-alkenyl-2H-indazoles starting from 2-(2-carbonylmethyl)-2H-indazoles, which are prepared by gallium/aluminium- and aluminium-mediated, direct, regioselective alkylation of indazoles with α-bromocarbonyl compounds. The structure of 3-(2H-indazol-2-yl)-2H-chromen-2-one was proven by X-ray crystallography. The styrene- and coumarin-2H-indazoles produced by using the new method were found to have interesting fluorescence properties.

Regioselective synthesis of 2H-indazoles through Ga/Al- and Al-mediated direct alkylation reactions of indazoles.

A procedure has been developed for the regioselective, high yielding synthesis of 2H-indazoles that involves direct alkylation of indazoles with various allyl and benzyl bromides, and α-bromocarbonyl compounds.

Synthesis of hexahydro-1H-isoindole derivatives from arylacyl bromides via homoallenic bromohydrins.

A procedure has been developed for the concise synthesis of hexahydro-1H-isoindole derivatives starting from phenacyl bromides. The approach employs a sequence involving an initial indium-mediated allenylation reaction of an arylacyl bromide with propargyl bromide. This process is followed by FeBr3-mediated SN2'-type substitution reaction of the formed homoallenic bromohydrin to produce a 2,5-dibromo-4-aryl-1,3-pentadiene, which then is subjected to a sequential, one-pot N-alkylation reaction with N-allyl-N-(p-tosyl)amine and a highly diastereoselective intramolecular Diels-Alder reaction of the formed ene-diene to generate the target hexahydro-1H-isoindole.

γ-Halo-enones: a method for their synthesis from arylacyl halides and their application to the preparation of five-membered ring heterocycles.

A simple method has been developed for synthesis of γ-halo-enones. The approach employs a sequence involving initial indium-mediated allenylation reactions of phenacyl halides with propargyl bromide. This process is followed by acid-promoted rearrangement reactions of the formed homoallenic halohydrins.

Nitroalkenes as carbonyl surrogates in arylmethyl-homoallylic alcohol forming one-pot allylation reactions in water.

A simple and practical approach has been developed for conducting direct, homoallylic alcohol forming allylation reactions of nitroalkenes in water. Employing the new method, various arylmethyl-homoallylic alcohols can be produced from the corresponding, readily prepared β-nitrostyrenes.

SnCl2/TiCl3-mediated deoximation of oximes in an aqueous solvent.

A simple procedure for SnCl(2)/TiCl(3)-mediated deoximation of ketoximes in an aqueous solvent is reported. Under the conditions developed in this effort, various ketones and aldehydes are produced in good to excellent yields.

Methods for the preparation of allenes employing indium- and zinc-mediated dehalogenation reactions in aqueous solutions.

Simple and mild methods for the synthesis of allenes, employing indium- and zinc-mediated dehalogenation reactions of vicinal dihalides in an aqueous solvent, are described. By using these procedures, various allenylmethyl aryl ethers and monosubstituted allenes have been prepared in good to excellent yields.

Tin mediated allylation reactions of enol ethers in water.

Under tin-mediated Barbier-type reaction conditions, hydration of enol ethers takes place to form aldehydes that undergo allylation reactions. By using this process, various homoallylic alcohols and 2-halohomoallylic alcohols are produced in good to excellent yields.

Exceptionally active yttrium-salen complexes for the catalyzed ring opening of epoxides by TMSCN and TMSN(3).

Halide or alkoxide free yttrium-salen complexes are excellent catalysts for the ring opening of epoxides mediated by TMSCN and TMSN3. Substrate to catalyst ratios up to 10000 have been realized in these potentially useful reactions, which can be run under solvent-free conditions. Even though the enantioselectivities for the TMSCN-mediated reaction remains modest (best 77% ee), these studies with a highly tunable ligand system may provide further impetus for work in this important area of catalysis.

Fe/Cr- and Co/Cr-mediated catalytic asymmetric 2-haloallylations of aldehydes.

The first example to couple aldehydes and 3-bromo-2-halopropenes in a catalytic asymmetric manner is reported. The coupling reaction is effected by the use of a chiral sulfonamide-Cr complex (prepared in situ from 1d, CrBr3, Fe(III) or from Co(II), Et3N, and Mn), TMSCl, and 2,6-lutidine. The method reported here is operationally simple and scalable, furnishing 3-halohomoallylic alcohols with a synthetically useful level of enantiomeric excess.

Ligand-assisted rate acceleration in transacylation by a yttrium-salen complex. Demonstration of a conceptually new strategy for metal-catalyzed kinetic resolution of alcohols.

[reaction: see text]. Yttrium-salen complexes effect transacylation between enolesters and chiral secondary alcohols, resulting in varying degrees of kinetic resolution. Even though the enantioselectivity remains modest (k(fast)/k(slow) up to 4.