1,721,016 research outputs found
Indoloquinolizidine alkaloids. A highly stereoselective synthesis of (±)-deplancheine using a dienetricarbonyliron(0) complex
No full textAn efficient synthesis of (±)-deplancheine (1) is presented. Key steps include a tandem excited-state oxidation-cyclisation of the η4-diene complex (7), and a stereoselective double bond shift [(11) → (12)] induced by Fe2(CO)9
Catalytic oxidation of primary aromatic amines to the corresponding nitroso compounds by H2O2 and [Mo(O)(O2)2(H2O)(hmpa)] (hmpa = hexamethylphosphoric triamide)
No full text[Mo(O)(O2)2(H2O)(hmpa)] 1 catalyses the oxidation of primary aromatic amines to the corresponding nitroso derivatives, in the presence of H2O2 as oxidant
A specific and efficient synthesis of (±)-dihydrocorynantheol
No full textA specific and efficient synthesis of (±)-dihydrocorynantheol (1) is reported. Starting with the easily accessible imine (3), ring D was built via stereoselective reaction with the lactone (4a), thus providing the complete carbon skeleton of (1); subsequent elaboration gave the desired alkaloid (1)
Amination of benzylic C-H bonds by aryl azides catalysed by Co-II(porphyrin) complexes : a new reaction leading to secondary amines and imines
No full textCo-II(porphyrin) complexes catalyse the reaction of aromatic azides, ArN3, with hydrocarbons containing a benzylic group, (RRRCH)-R-1-R-2-C-3, to give the corresponding amines, (RRRC)-R-1-R-2-C-3-NHAr. When at least one of the R-1-R-3 substituents is hydrogen, the catalytic reaction proceeds further to give the imines (RRC)-R-1-C-2=NAr in good yields
Metal carbonyls catalysed reductive carbonylation of substituted nitrobenzenes in presence of alkenes as solvents
No full textSeveral nitrobenzene derivatives were submitted to reaction with carbon monoxide in alkene solvents in the presence of catalytic amounts of Ru3(CO)12. Ureas and amines were formed in this reaction, and the secondary amine derived from insertion of the nitrene intermediate at the allylic position of the alkene solvent was a secondary product. The influence of the electronic factor of the substituents on the urea vs. amine ratio is discussed
Oxidation of primary aromatic amines to nitro derivatives catalyzed by iron(III) and manganese(III) tetraaryl porphyrins
No full textThe oxidation of primary aromatic amines to the corresponding nitro derivatives has been observed in catalytic systems (turnovers/hour up to 18000) containing tert-butyl hydroperoxide and metallo-tetraaryl porphyrins (metal = FeIII or MnIII) in the presence of heterocyclic nitrogen bases acting as axial ligands
Allylic amination of unactivated olefins by nitroarenes, catalyzed by ruthenium complexes. A reaction involving an intermolecular C-H functionalization
No full textA reaction is reported, resulting in the allylic amination of an unactivated olefin, cyclohexene, by a nitroarene, catalyzed by Ru-3(CO)(12)/Ar-BIAN (Ar-BIAN = bis(arylimino)acenaphthene), under CO pressure. The reaction involves an intermolecular catalytic C-H functionalization by a transition metal complex. Best results (selectivity up to 81.9%, with a substrate/Ru-3(CO)(12) ratio = 50) are obtained by using nitroarenes bearing electron-withdrawing substituents and Ph-BIAN as a ligand. Other olefins can also be employed in place of cyclohexene. The reaction mechanism has been investigated. The reaction is first order in nitroarene and olefin, which is used as solvent in most cases, but the rate equation also contains an olefin-independent term. A rate acceleration by small amounts of toluene in the solvent mixture is due to a faster formation of Ru(CO)(3)(Ar-BIAN) from Ru-3(CO)(12) and Ar-BIAN in its presence. This last complex is in equilibrium with the active species Ru(Ar-BIAN)(CO)(2)(cyclohexene), and its direct reaction with the nitroarene accounts for the olefin-independent term in the rate law. The reaction of Ru(CO)(3)(Ar-BIAN) with nitroarenes gives Ru(CO)(2)(Ar-BIAN)(eta(2)-ArNO), which has been isolated in one case, but this complex is not an intermediate in the synthesis of allylamines. Coupling between a coordinated nitrosoarene and a coordinated olefin appears to be responsible for the C-N bond formation
Allylic: Amination of cyclohexene catalyzed by ruthenium complexes. A new reaction involving an intermolecular C-H functionalization
No full text- …
