1,720,997 research outputs found
Tsuji-Trost Type functionalization of allylic substrates with challenging Leaving Groups : recent developments
No full textThe Review reports the recent developments of palladium-catalyzed nucleophilic substitution of allylic alcohols and allylic amines used as electrophiles. The poor ability of the hydroxyl and amino groups to serve as good leaving groups has been overcome by the employment of additives which promote the palladium-catalyzed C-N and C-O bond cleavage. However, allylic alcohol and amine activation can be achieved by using appropriate catalytic systems or solvents, without any external activators. Significant expansion of the nucleophile scope allows to obtain various allylic compounds through the regio- and stereoselective formation of carbon-carbon and carbon-heteroatom bonds
Stereoselective synthesis of 1,3-substituted tetrahydroisoquinolines through palladium-catalyzed three-component reaction
No full textChiral 1,3-substituted 1,2,3,4-tetrahydroisoquinolines have been synthesized in acceptable yield and diastereoselectivity through a three component reaction, starting from aromatic halides, enantiopure bromoalkyl derivatives and methyl acrylate, under palladium catalysis
A simple synthesis of (Z) 3-arylmethylene-2-methyl-1,2-benzothiazin-4-(3H) ones 1,1-dioxide
No full textA one-pot approach to 3-arylmethylene-2-methyl-1,2-benzothiazin-4-(3H)ones 1,1-dioxide (3) starting from 2-methyl-1,2-benzothiazin-4-one and the appropriate aldehydes, in the presence of sodium methoxide/methanol, is described
Steric configuration and reactivity of 2-benzylidene-4-methyl-2H-1,4-benzoxazin-3(4H)-one
No full textThe reactivity of 2-benzylidene-4-methyl-2H-1,4-benzoxazin-3(4H)-one (1) towards N- and C-nucleophiles, nucleophilic and electrophilic alkenes, dienes and 1,3-dipoles was investigated. Nitrones (2) reacted with 1 giving through a regioselective process a mixture of the two diastereoisomeric spiro compounds (3) and (4) whose structure and relative steric configuration have been assigned on the basis of 1H and 13C nmr data
Reaction of 2,4-diphenyl-4,5-dihydro-1,3-oxazol-5-one with 4-phenyl-N-tosyl-1-azabuta-1,3-diene : C=C versus C=N double bond addition
No full textThe reaction of 2,4-diphenyl-4,5-dihydro-1,3-oxazol-5-one 1 with 4-phenyl-N-tosyl-1-azabuta-1,3-diene 2 has been investigated using different experimental conditions. Whereas at room temperature the kinetically controlled Michael adduct 3 was isolated, at 110°C products 4, 5, 6 and 7 were obtained. Their formation is explained according to 1,3-dipolar cycloaddition and nucleophilic addition, both related to the dual nature of the azlactone 1. The reactivity of azlactone 1 towards imine 2, which is different from that observed with N-alkyl- and N-aryl-1-azabuta-1,3-dienes, is explained on the basis of the electronic effects exerted by the tosyl substituent
Reaction of mesoionic compounds deriving from cyclic N-acyl-alpha-aminoacids with N-(phenylmethylene)benzenesulfonamide
No full textWe studied the behaviour of bicyclic mesoionic compounds derived from the cyclodehydration of cyclic N-acyl-α-aminoacids 1-4 with N- (phenylmethylene)benzenesulfonamide 5. The reaction affords spirocyclic β- lactams and/or imidazo-condensed products (the 1,3-dipolar cycloaddition adducts) depending on the experimental conditions and on the nature of the substituent R on the mesoionic ring
Enantioselective synthesis of 1-vinyltetrahydroisoquinolines through palladium-catalysed intramolecular allylic amidation with chiral PhthalaPhos ligands
No full textThe PhthalaPhos ligands, chiral BINOL monophosphites endowed with a phthalamide group, have been screened in the synthesis of 1-vinyltetrahydroisoquinolines by intramolecular palladium-catalysed asymmetric allylic amidation (AAA) of achiral tosylamidocarbonates. Identification of the best ligand followed by optimisation of the reaction conditions allowed the desired product to be obtained with up to 83% ee. Remarkably, the reaction is stereoconvergent, affording the same enantiomer of the desired product regardless of the geometry of the allylic carbonate’s double bond, which allows, in principle, the use of E/Z mixtures
2-(Tosylamino)benzyltrimethylammonium halides as precursors of 2-substituted indoles
No full textThe reactions of 2-(tosylamino)benzyltrimethylammonium halides (1) with dimethylsulfonium 2-oxo-2-phenylethylide (6b), dimethylsulfonium 2-ethoxy-2-oxo-ethylide (6c) and dimethylsulfonium cyanomethylide (6d) are useful synthetic routes to 2-substituted indoles (8b-d). The relationship between reaction conditions and selectivity is discussed
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