[Show abstract][Hide abstract] ABSTRACT: ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
[Show abstract][Hide abstract] ABSTRACT: Pd-N-heterocyclic carbene (NHC)-catalyzed Buchwald-Hartwig amination protocols mediated by Pd-PEPPSI precatalysts is described. These protocols provide access to a range of hindered and functionalized drug-like aryl amines in high yield with both electron-deficient and electron-rich aryl- and heteroaryl chlorides and bromides. Variations in solvent polarity, base and temperature are tolerated, enhancing the scope and utility of this protocol. A mechanistic rationalization for base strength (pKb) requirements is also provided.
[Show abstract][Hide abstract] ABSTRACT: An easily employed, highly versatile Kumada-Tamao-Corriu (KTC) protocol utilizing the PEPPSI (Pyridine, Enhanced, Precatalyst, Preparation, Stabilization and Initiation) precatalysts 1 and 2 is detailed. The ease-of-use of these catalysts and the synthesis of a wide range of hindered biaryls, large coupling partners and drug-like heterocycles, in high yield, makes the PEPPSI-KTC protocol very attractive. The high reactivity of the PEPPSI system allowed a tetra-ortho-substituted heterocycle, 11 to be synthesized at room temperature for the first time using any protocol. The PEPPSI protocols also tolerated the Boc protecting group and phenols required no protection in modified conditions. A relatively large scale (10 g) reaction was also performed with no loss in performance. Furthermore, PEPPSI-IPr, 1, was compared to previously reported highly active phosphine ligands 42, 43, and 44 and was shown to result in significantly better yields under identical conditions. Finally, we demonstrated that the PEPPSI catalyst system is very adept at performing sequential KTC coupling reactions, analogous to multicomponent reactions, which allow complex polyaryl and polyheteroaryl architectures to be produced in one single operation.