Pyridazine N-Oxides as Precursors of Metallocarbenes: Rhodium-Catalyzed Transannulation with Pyrroles
摘要:
Pyridazine N-oxides are used for the first time as precursors of metallocarbenes. These nitrogen-rich heterocycles led to the discovery of a novel acceptor and donor-acceptor enalcarbenoids. The synthetic utility of these metallocarbenes was demonstrated in the rhodium-catalyzed denitrogenative transannulation of pyridazine N-oxides with pyrroles to the valuable alkyl, 7-aryl, and 7-styryl indoles. The transannulation strategy was applied to the synthesis of a potent anticancer agent.
Pyridazine N-Oxides as Precursors of Metallocarbenes: Rhodium-Catalyzed Transannulation with Pyrroles
摘要:
Pyridazine N-oxides are used for the first time as precursors of metallocarbenes. These nitrogen-rich heterocycles led to the discovery of a novel acceptor and donor-acceptor enalcarbenoids. The synthetic utility of these metallocarbenes was demonstrated in the rhodium-catalyzed denitrogenative transannulation of pyridazine N-oxides with pyrroles to the valuable alkyl, 7-aryl, and 7-styryl indoles. The transannulation strategy was applied to the synthesis of a potent anticancer agent.
Facile, One-Step Production of Niacin (Vitamin B3) and Other Nitrogen-Containing Pharmaceutical Chemicals with a Single-Site Heterogeneous Catalyst
作者:Robert Raja、John Meurig Thomas、Michael Greenhill-Hooper、Steven V. Ley、Filipe A. Almeida Paz
DOI:10.1002/chem.200701679
日期:2008.3.7
Niacin (3-picolinic acid), which is extensively used as vitaminB3 in foodstuffs and as a cholesterol-lowering agent, along with other oxygenated products of the picolines, 4-methylquinoline, and a variety of pyrimidines and pyridazines, may be produced in a single-step, environmentally benign fashion by combining single-site, open-structure, heterogeneouscatalysts with a solid source of active oxygen
Despite many efforts, one of the smallest heterocycles containing two nitrogen atoms, pyridazine, could not be converted to its N,N-dioxide (see, however, Nakadate et al. Chem. Pharm. Bull. 1970, 18, 1211–1218). HOF·CH3CN, made easily from diluted fluorine, was able to accomplish this task in a fast reaction with good yields.