Nouvelle méthode de préparation d'éthers vinyliques à partir d'acétals

2-Methoxy-5-(2-Bromoethyloxy)-2,5-Dihydrofuran: A Useful Building Block for the Synthesis of Dihydro- and Tetrahydro-Furan Moieties

New syntheses of structures of biological interest containing the tetrahydro-, dihydro- and furo-furan rings are reported employing simple experimental procedures and mild reaction conditions.

Lewis acid catalysis and Green oxidations: sequential tandem oxidation processes induced by Mn-hyperaccumulating plants

Among the phytotechnologies used for the reclamation of degraded mining sites, phytoextraction aims to diminish the concentration of polluting elements in contaminated soils. However, the biomass resulting from the phytoextraction processes (highly enriched in polluting elements) is too often considered as a problematic waste. The manganese-enriched biomass derived from native Mn-hyperaccumulating plants of New Caledonia was presented here as a valuable source of metallic elements of high interest in chemical catalysis. The preparation of the catalyst Eco-Mn1 and reagent Eco-Mn2 derived from Grevillea exul exul and Grevillea exul rubiginosa was investigated. Their unusual polymetallic compositions allowed to explore new reactivity of low oxidative state of manganese-Mn(II) for Eco-Mn1 and Mn(IV) for Eco-Mn2. Eco-Mn1 was used as a Lewis acid to catalyze the acetalization/elimination of aldehydes into enol ethers with high yields; a new green and stereoselective synthesis of (-)-isopulegol via the carbonyl-ene cyclization of (+)-citronellal was also performed with Eco-Mn1. Eco-Mn2 was used as a mild oxidative reagent and controlled the oxidation of aliphatic alcohols into aldehydes with quantitative yields. Oxidative cleavage was interestingly noticed when Eco-Mn2 was used in the presence of a polyol. Eco-Mn2 allowed direct oxidative iodination of ketones without using iodine, which is strongly discouraged by new environmental legislations. Finally, the combination of the properties in the Eco-Mn catalysts and reagents gave them an unprecedented potential to perform sequential tandem oxidation processes through new green syntheses of p-cymene from (-)-isopulegol and (+)-citronellal; and a new green synthesis of functionalized pyridines by in situ oxidation of 1,4-dihydropyridines.

Regioselective Synthesis of 5-Alkylsalicylates, 5-Alkyl-2-hydroxy-acetophenones, and 5-Alkyl-2-hydroxy-benzophenones by [3 + 3] Cyclization of 1,3-Bis(silyl enol ethers) with 2-Alkyl-1,1,3,3-tetraethoxypropanes

A variety of 5-alkylsalicylates, 5-alkyl-2-hydroxy-acetophenones, and 5-alkyl-2-hydroxy-benzophenones was regioselectively prepared by TiCl4 mediated formal [3 + 3] cyclization of 1,3-bis(silyl enol ethers) with 2-alkyl-1,1,3,3-tetraethoxypropanes.

Lewis acid-directed cyclocondensation of piperidone enol ethers with 2-methoxy-4-(N-phenylsulfonyl)-1,4-benzoquinoneimine: a new regioselective synthesis of oxygenated carbolines

Lewis acid-directed cyclocondensations of piperidone enol ethers with 2-methoxy-4-(N-phenylsulfonyl)-1,4-benzoquinoneimine are reported. Benzofurans are obtained with BF3.OEt2 as a promoter, whereas use of excess amounts of TiCl4:Ti(OiPr)4 leads to tetrahydrocarbolines. The latter reactions provide expedient routes to oxygen-substituted tetrahydrocarbolines and carbolines. As applications of this new methodology, the preparations of 1-[3-(dimethylamino)propyl]amino-7-methoxy- and 1-[3-(dimethylamino)propyl]amino-7,8-dimethoxy-5H-pyrido[4,3-b]indoles are described.