Cyclometallated Gold(III) Complexes as Effective Catalysts for Synthesis of Propargylic Amines, Chiral Allenes and Isoxazoles

Abstract

Cl 2 ] 1a-l (HC _ N = arylpyridines) and a PEG-linked complex 1m were synthesized. Complexes 1a-m are effective in catalyzing the synthesis of propargylic amines, chiral allenes and isoxazoles. Six-membered ring cyclometallated goldA C H T U N G T R E N N U N G (III) complexes 1f-l exhibited higher catalytic activity than five-membered ring cyclometallated goldA C H T U N G T R E N N U N G (III) complexes 1a-e. The diastereoselectivity of propargylic amines could be tuned by using chiral aldehyde and/ or amine substrates. Excellent enantioselectivities (90-98% ee) were achieved in chiral allene synthesis. Chiral allene racemization could be minimized by using 1f as catalyst. The PEG-linked catalyst 1m is the most catalytically active towards synthesis of propargylic amines, in which case a product turnover of 900 was achieved. Moreover, 1m could be repeatedly used for 12 reaction cycles, leading to an overall turnover number of 872.

Cyclometalated Gold(III) Complexes: Synthesis, Reactivity, and Physicochemical Properties

“…More recently,i nvestigations have also showcased catalytic applications of these complexes in the synthesis of chiral allenes, oxazoles,and isoxazoles. [93,94] In 2015, Youa nd co-workers described the utilization of the cyclometalated [(C^N)Au(X)(Y)] complexes 101 a and 101 b to study the mechanism of the gold-catalyzed oxidative C À Ha rylation of 2-aryl pyridines with aryl boronic acids (Scheme 28). [95] Thes toichiometric reaction of 101 a or 101 b with phenylboronic acid in the presence of KF delivered the desired cross-coupling product 102 in excellent yield.…”

“…Complex 56 proved to be highly robust so that ten successive cycles could be performed with overall turnover numbers of >800. More recently, investigations have also showcased catalytic applications of these complexes in the synthesis of chiral allenes, oxazoles, and isoxazoles …”

Direct intramolecular carbon(sp2)–nitrogen(sp2) reductive elimination from gold(iii)

“…Compounds 1 and 1′ were prepared according to literature procedures and well characterized prior to usage. 43,44 All reactions were carried out under normal atmospheric conditions. Deuterated solvents were purchased from Cambridge Isotope Laboratories (Andover, MA).…”

Synthesis of 3,5-Disubstituted Isoxazoles and Isoxazolines in Deep Eutectic Solvents

“…Different metallic derivatives have been used to perform the regioselective cycloaddition reaction, including aluminum, 25 40 and Pb(OAc) 2 . 41 Conversely, in the case of cyclopentadienyl ruthenium derivatives, 42 the regioselective formation of the related 4,5-disubstituted heterocycles was observed.…”