RESUMO
A procedure has been developed for the concise, stereoselective synthesis of (Z)-5-bromo-4-aryl-pent-3-en-1-ynes through Sc(OTf)3 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.
RESUMO
A new strategy for cyclopenta[b]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[b]furan targets.
Assuntos
Compostos Bicíclicos Heterocíclicos com Pontes/síntese química , Furanos/síntese química , Iodo/química , Iodobenzenos/química , Catálise , Ciclização , Isomerismo , Estrutura Molecular , OxirreduçãoRESUMO
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.
RESUMO
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.
RESUMO
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. The new method can be incorporated into routes for the efficient synthesis of various five-membered heterocyclic compounds.
RESUMO
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 ß-nitrostyrenes.
RESUMO
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.
Assuntos
Oximas/química , Solventes/química , Compostos de Estanho/química , Titânio/química , Água/química , Acetofenonas/química , Catálise , HidróliseRESUMO
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.
Assuntos
Alcadienos/síntese química , Antineoplásicos/síntese química , Química Farmacêutica/métodos , Éteres/síntese química , Química Verde , Halogênios/química , Alcadienos/farmacologia , Antineoplásicos/farmacologia , Catálise , Éteres/farmacologia , Humanos , Índio/química , Estrutura Molecular , Neoplasias/tratamento farmacológico , Soluções , Estereoisomerismo , Água , Zinco/químicaRESUMO
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.
RESUMO
[reaction: see text] The enantioselective conjugate addition of alpha-substituted malonates to aromatic nitroalkenes generates a stereocenter at the carbon bearing the aromatic group and an adjacent prochiral center from the alpha-substituted malonate. Nitro reduction followed by diastereoselective cyclization provides pyrrolidinones with two contiguous stereocenters, one of which is quaternary. This sequence was used for the preparation of the PDE4 inhibitor IC86518. Additional examples of the enantioselective Michael addition illustrate the scope of the reaction.
Assuntos
3',5'-AMP Cíclico Fosfodiesterases/antagonistas & inibidores , Alcenos/química , Malonatos/química , Nitrocompostos/química , Pirrolidinas , Nucleotídeo Cíclico Fosfodiesterase do Tipo 4 , Estrutura Molecular , Pirrolidinas/síntese química , Pirrolidinas/química , Pirrolidinas/farmacologia , EstereoisomerismoRESUMO
A series of acyl silanes including aliphatic-, aromatic-, and bis-acyl silanes, as well as the acyl silanes bearing other substituents such as a bromine atom and alkenyl, succinimide, and carbonyl groups, were prepared, and their reactions with samarium diiodide or tributylstannane were studied. The reactions of acyl silanes occurred in various manners such as reductions, reductive alkylations, intramolecular radical cyclizations, pinacol couplings, aldol reactions, and Tishchenko reactions, depending on the nature of substrates and reaction conditions. Acyl silanes were generally reduced to give the corresponding alpha-silyl alcohols without transfer of silyl groups. Intramolecular radical cyclizations of 5-hexenoyl silanes and 1-silyl-1,5-pentanedione were realized to give alpha-silyl cyclopentanols and 1,2-cyclopentanediol derivatives, respectively. On treatment with samarium diiodide in tetrahydrofuran, 1-(trimethylsilyl)-1,6-hexanedione underwent a pinacol coupling reaction in the presence of t-BuOH, whereas it underwent a Tishchenko reaction in the presence of MeOH. The Tishchenko reaction of 1-silyl-1,5-pentanedione gave a delta-silyl-delta-lactone. On treating with samarium diiodide, 1-(trimethylsilyl)-1,5-hexanedione and 1,5-bis(trimethylsilyl)-1,6-hexanedione, underwent, respectively, intramolecular aldol reactions.