143 research outputs found
Rhodium(II)-Catalysed Intramolecular O-H Insertion of alpha-Diazo-gamma-Azido-delta-Hydroxy-beta-Ketoesters: Evidence for a Novel Sigmatropic Rearrangement of an Allylic Azide Intermediate
The Rh2(OAc)4 catalyzed intramolecular O-H insertion reaction of delta-hydroxy-alpha-diazoesters affords 3(2H)-furanone-2-carboxylates in good yield but with moderate selectivity (d.e. ca 60%). The initially formed 2,5-substituted cis-furanones were found to epimerize to the corresponding 2,5-trans isomers when subjected to silica gel chromatography. The Rh2(OAc)4 catalyzed decomposition of gamma-azido-delta-hydroxy-alpha-diazoesters also furnished 3(2H)-furanone-2-carboxylates. These compounds are derived by a sequential O-H insertion reaction followed by a concerted [3,3]-sigmatropic shift of the allylic azide intermediate
An approach to the cephalotaxine ring skeleton using an ammonium ylide/Stevens [1, 2]-rearrangement
N-[(2-Chloro-3-quinolyl)methyl]-4-fluoroaniline
In the title compound, C16H12ClFN2, the dihedral angle between the quinoline ring system and the flourophenyl ring is 86.70 (4)°. In the crystal, molecules are linked into chains along the a axis by N—H⋯N hydrogen bonds. In addition, C—H⋯π interactions involving the two benzene rings are observed
Synthesis of Polycyclic Ring Systems Using Transition Metal Catalyzed Cyclizations of Diazo Alkynyl Ketones
The rhodium(II)-catalyzed reaction of α-diazo ketones bearing tethered alkyne units represents a new and useful method for the construction of a variety of substituted cyclopentenones. The process proceeds by addition of the rhodium-stabilized carbenoid onto the acetylenic π-bond to give a vinyl carbenoid intermediate. The resulting rhodium complex undergoes a wide assortment of reactions including cyclopropanation, 1,2-hydrogen migration, CH-insertion, addition to tethered alkynes and ylide formation. When 2-alkynyl-2-diazo-3-oxobutanoates were treated with a Rh(II)-catalyst, furo[3,4-c]furans were formed in excellent yield
Gold- and silver-mediated cycloisomerizations of N-propargylamides
Substituted N-propargylamides have proven to be valuable substrates for alkyne-activated cycloisomerization reactions. N-Tosyl-N'-propargylurea underwent reaction with AuCl3 to give the corresponding dihydroimidazolone, while N-propargyl-3-oxobutanamides and esters were used to construct furanyl fused pyrrolldinones and dihydrofuranones via Ag(I)-mediated alkyne activation
Preparation of 2-amido substituted furans using the Curtius re-arrangement of furan-2-carbonyl azide
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