Ligand Effects in the Rhodium(II)-Catalyzed Reactions of .alpha.-Diazoamides. Oxindole Formation is Promoted by the Use of Rhodium(II) Perfluorocarboxamide Catalysts
摘要:
An improved procedure for the preparation of ethyl 2-diazomalonyl chloride ws developed which involves the reaction of ethyl diazoacetate with triphosgene. Using this diazo acid chloride, it was possible to prepare a variety of diazoamides from substituted amines. The rhodium(II)-catalyzed decomposition of these diazoamides was studied in order to probe the chemoselectivity of the carbenoid intermediates in intramolecular insertion reactions. Rhodium(II) acetate decomposition of N-benzyl-2-diazo-N-phenylmalonamic acid ethyl ester resulted in intramolecular C-H insertion to give ethyl 1,4-diphenyl-2-oxoazetidine-3-carboxylate. By changing the catalyst ligand to trifluoroacetamide, beta-lactam formation was completely suppressed in favor of the aromatic C-H insertion which produces an oxindole as the only detectable product. The competition between aliphatic and aromatic carbon-hydrogen insertion of 2-diazo-N-phenylmalonamic acid ethyl ester provides another example of ligand effectiveness in controlling chemoselectivity in dirhodium(II)-catalyzed metal carbene reactions. Thus, treatment of the N-isobutyldiazoanilide with rhodium(II) acetate results in exclusive aliphatic C-H insertion giving 4,4-dimethyl-2-oxo-1-phenylpyrrolidine-3-carboxylic acid ethyl ester, while the perfluorobutyramide ligand promotes oxidinole formation by aromatic C-H insertion. Several other rhodium(II)-catalyzed reactions were studied and were found to be highly catalyst dependent, rhodium(II) perfluorocarboxamides promoting aromatic C-H insertion, and hence oxindole formation, over O-H insertion, cyclization onto adjacent triple bonds, or cyclization to generate 1,3-dipolar intermediates.
Studies towards the Synthesis of AlkylN-(4-Nitrophenyl)-3/2-oxomorpholine-2/3-carboxylates
摘要:
AbstractThe syntheses of methyl 4‐(4‐nitrophenyl)‐3‐oxomorpholine‐2‐carboxylate (3a) and ethyl 4‐(4‐nitrophenyl)‐2‐oxomorpholine‐3‐carboxylate (5b), important building blocks for the synthesis of factor Xa inhibitor rivaroxaban analogs with potential dual antithrombotic activity, via Rh2(OAc)4‐catalyzed OH and NH carbene insertion reactions are described.
Ethyl 2-diazomalonyl chloride. An efficient diazoacylating reagent
作者:Joseph P. Marino、Martin H. Osterhout、Alan T. Price、Scott M. Sheehan、Albert Padwa
DOI:10.1016/s0040-4039(00)75980-6
日期:1994.1
Ethyl 2-diazomalonyl chloride readily reacts with aromatic and aliphatic amines, alcohols, thiols, and amides for form a variety of alpha-diazo carbonyl species.