Synthesis of Indolizine and Pyrrolo[1,2- a]azepine Derivatives via a Gold(I)-Catalyzed Three-Step Cascade
Linear N-alkenyl or alkynyl N-sulfonyl 1-aminobut-3-yn-2-ones are converted into bicyclic indolizines and pyrrolo[1,2-a]azepine-type alkaloids upon gold(I) catalysis (17 examples, 10-85%). The reaction cascade allowed formation of C-N, O-S, and C-C bonds via a cycloisomerization/sulfonyl migration/cyclization process using 10 mol % of [(2-biphenyl)di-tert-butylphosphine]gold(I) triflimide complex in dichloromethane.
On the silver effect and the formation of chloride-bridged digold complexes
Abstraction of chloride anion from Au(I) complexes such as JohnPhosAuCl in noncoordinating solvents with 1 equiv of a silver salt, or even larger amounts, leads to the formation of chloride-bridged dinuclear gold(I) complexes, irrespective of the counteranion, which are substantially less reactive as catalysts. This incomplete removal of chloride ligand could lead to false negative results when using the in situ generation of the gold(I) active species by silver-promoted chloride abstraction.
Synthesis of Substituted Quinolizidines via a Gold-Catalyzed Double Cyclization Cascade
A novel synthesis of quinolizidines by a cationic gold-catalyzed double cyclization cascade has been developed. The reaction was initiated by the gold-catalyzed 6-exo-dig cyclization of ynamides, which was followed by a second cyclization of an enamide intermediate to provide the corresponding quinolizidine derivatives. The utility of this reaction was demonstrated by application to the synthesis of multi-substituted quinolizidines and by the total synthesis of a quinolizidine alkaloid, (±)-lupinine.
Gold catalysis: Biarylphosphine ligands as key for the synthesis of dihydroisocoumarins
Agold-catalyzed phenol synthesis was successfully used in the synthesis of dihydroisocoumarins for the first time.Alarge number of gold(I) complexes were prepared and tested; only complexes based on the biarylphosphine motif were successful. CSIRO 2014.
Hashmi, A. Stephen K.,Bechem, Benjamin,Loos, Annette,Hamzic, Melissa,Rominger, Frank,Rabaa, Hassan
p. 481 - 499
(2014/04/03)
Gold-catalyzed oxidative cyclizations on 1,4-enynes: Evidence for a γ-substituent effect on Wagner-Meerwein rearrangements
Gold-catalyzed oxidative cyclizations of 1,4-enynes were used to study the γ-effect on the Wagner-Meerwein rearrangement. Both experimental and theoretical work disclose that a gold substituent in the γ-position can direct a stereospecific 1,2-shift of the anti-β-substituent regardless of its intrinsic properties. Copyright
Ghorpade, Satish,Su, Ming-Der,Liu, Rai-Shung
supporting information
p. 4229 - 4234
(2013/05/08)
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