ABSTRACT
The vanadium-catalyzed oxidative coupling of substituted 2-arylimidiazo[1,2-a]pyridines to N-methylmorpholine oxide, which acts as both a coupling partner and an oxidant, has been achieved. This reaction was applied to various substituted imidiazo[1,2-a]pyridine and indole substrates, resulting in yields as high as 90%. Mechanistic investigations indicate that the reaction may proceed via a Mannich-type process. This work demonstrates how oxidative aminomethylation can be used as a useful method to introduce tertiary amines into heterocycles, thus providing an alternative method for conventional Mannich-type reactions.
Subject(s)
Heterocyclic Compounds, 3-Ring/chemistry , Heterocyclic Compounds, 4 or More Rings/chemical synthesis , Imidazoles/chemistry , Morpholines/chemistry , Pyridines/chemistry , Vanadium/chemistry , Catalysis , Heterocyclic Compounds, 4 or More Rings/chemistry , Molecular Structure , Oxidants/chemistry , Oxidation-Reduction , Oxidative CouplingABSTRACT
In(OTf)3 catalyzed microwave-assisted alkenylation of methoxyphenols was investigated. Exclusive formation of either indenes or chromenes was observed depending on the position of the methoxy group on phenol. The structures of 1H-inden-4-ol derivatives (4a-e) and 4H-chromene derivatives (5a-j) were established by NMR ((1)H & (13)C) and high-resolution mass spectra, which were further supported by single crystal X-ray analysis of 4c and 5a.
ABSTRACT
An efficient one-pot sequential procedure is described for the synthesis of novel azole-fused quinazolines through Pd/Cu co-catalyzed, Ullmann-type coupling followed by cross dehydrogenative coupling of various azoles such as 1H-imidazole, 1H-benzimidazole and 1H-1,2,4-triazole with 2-(2-bromophenyl)-1H-imidazole/benzimidazoles. The developed strategy has offered good yields (52-81%) of diverse N-fused tetra-, penta- and hexa-cyclic frameworks in a single step.
