Diastereoselective alkylation of chiral derivatives of acetoacetic acid
作者:Marcial Moreno-Mañas、Rosa M. Sebastian、Adelina Vallribera、Elies Molins
DOI:10.1016/0040-4020(95)00643-m
日期:1995.9
N-acetoacetyl-(S)-4-benzyloxazolidin-2-one and N-acctoacetyl-(R)-bornane-10,2-sultam are alkylated at the C-α of the acctoacetyl moiety with significant diastereoisomeric excesses. The diastereoisomers are in general easily separable and configurationally fairly stable.
Relative syn 1,2-hydrazinoalcohols have been prepared through diastereoselective Ni(II)-catalyzed Michael addition of chiral derivatives of acetoacetic acid and of 3-oxostearic acid to dialkyl azodicarboxylates, followed by stereoselective reduction of the keto function.
Nickel(II)-catalyzed Michael additions. Formation of quaternary centers and diastereoselective addition of enantiopure N -acetoacetyl-4-benzyloxazolidin-2-one
Ni(acac)2 and Ni(salicylaldehydate)2 are effective catalysts for conjugate additions of 2-methyl-1,3-dicarbonyl compounds to Michael acceptors. Significant diastereomeric excesses are obtained in the Michael additions of enantiopure N-acetoacetyl-4-benzyloxazolidinones. Reaction of the latter compound with aryl isocyanates affords unsymmetrical diamides of malonic acid.
Reaction of Hydrazines with N-Acetoacetyl Derivatives of (4S)-4-Benzyloxazolidin-2-one and (2R)-Bornane-10,2-sultam in Very Acidic Media to Give Pyrazoles Retaining the Chiral Moiety at C-3(5)
作者:Marcial Moreno-Mañas、Rosa María Sebastián、Adelina Vallribera、Francesca Carini
DOI:10.1055/s-1999-3683
日期:——
Reaction of hydrazines with acetoacetamides affords pyrazoles retaining the amine moiety. Evans oxazolidinone and Oppolzer sultam have been incorporated into pyrazoles.
Cobalt-mediated alkylation of (4R) and (4S)-3-acetoacetyl-4-benzyloxazolidin-2-ones. Preparation of enantiopure diphenylmethyl-, 9-fluorenyl- and (1-adamantyl)glycines
The Co(II) complexes of (4R) and (4S)-3-acetoacetyl-4-benzyloxazolidin-2-ones are alkylated diastereoselectively with diphenylmethyl, 9-fluorenyl, and 1-adamantyl bromide. The resulting products are converted into enantiopure α-substituted glycines. Similar results are obtained by alkylation of the free acetoacetyloxazolidinones under Co(II)-catalysis.