Efficient Access to Cyclic Ureas via Pd-Catalyzed Cyclization
摘要:
An efficient regioselective method for the preparation of structurally diverse imidazopyridinones and benzoimidazolones starting from readily available and economical starting materials is described. High-yielding reductive alkylation of electron-deficient o-haloarylamines followed by treatment with inexpensive N-chlorosulfonyl isocyanate afforded primary ureas in good overall yields. A Pd-catalyzed urea cyclization reaction furnished imidazopyridinones and benzoimidazolones in excellent yields. Overall, the developed chemistry provides rapid access to pharmaceutically important heterocyclic compounds with high efficiency.
An expedient, catalytic method for the synthesis of diverse azaindoles and indoles, starting from readily available and inexpensive starting materials, is described. Conditions were developed for effective reductive alkylation of electron-deficient o-chloroarylamines, substrates previously viewed as poor partners in this reaction. The derived N-alkylated o-chloroarylamines were elaborated to N-alkylazaindoles and N-alkylindoles via a novel one-pot process comprising copper-free Sonogashira alkynylation and a base-mediated indolization reaction.
An Improved Synthesis of Imidazo[4,5-<i>b</i>]pyridines and Imidazo[4,5-<i>b</i>]pyrazines by Palladium Catalyzed Amidation using Xantphos in a 1,4-Dioxane:<i>tert</i>-Amyl Alcohol Solvent System
作者:Adam J. Rosenberg、Ijaz Ahmed、Robert J. Wilson、Theresa M. Williams、Lauren Kaminsky、Daniel A. Clark
DOI:10.1002/adsc.201400465
日期:2014.11.3
AbstractHerein an improved protocol for the synthesis of imidazo[4,5‐b]pyridines and imidazo[4,5‐b]pyrazines using a palladium‐catalyzed amidation that utilizes Xantphos as an ancillary phosphine ligand is reported. The use of a binary solvent system comprised of 1,4‐dioxane and tert‐amyl alcohol was crucial in eliminating unwanted by‐products.magnified image