Strategic Approach on N‐Oxides in Gold Catalysis – A Case Study

Abstract

An extensive kinetic study of selected key reactions of (oxidative) gold catalysis concentrates on the decrease of the catalytic activity due to inhibition of the gold(I) catalyst caused by pyridine derivatives that are obtained as by-products if N-oxides are applied as oxygen donors. The choice of the examined pyridine derivatives and their corresponding N-oxides has been made regardless of their commercial availability; particular attention has been paid to the practical benefit which up to now has been neglected in most of the reaction screenings. The test reactions were monitored by GC and 1 H NMR spectroscopy. The received reaction constants provide information concerning a correlation between the electronic structure of the heterocycle and the catalytic activity. Based on the collected kinetic data, it was possible to develop a basic set of three N-oxides which have to be taken into account in further oxidative gold(I)-catalyzed reactions.

Gold(I)-Catalyzed Reactivity of Furan-ynes with N-Oxides: Synthesis of Substituted Dihydropyridinones and Pyranones

“…α-Oxo gold(I) carbenes can undergo several reaction pathways, including cyclopropanations, migrations, ring expansions, insertions, and reactions with nucleophiles. 7 …”

Water Can Accelerate Homogeneous Gold Catalysis

“…[42][43] The selection of the N-oxides was based on our recent work. [44] For the present study, we examined the efficient 8-methylquinoline N-oxide 6 a reagent, the fast-reacting 3,5-dibromopyridine N-oxide 6 b and pyridine N-oxide 6 c as reference compounds.…”

Gold(I)‐Catalyzed Cycloisomerization of 3‐Alkoxyl‐1,6‐diynes: A Facile Access to Bicyclo[2.2.1]hept‐5‐en‐2‐ones

“…Simple salts like AuCN, AuCl, and KAuBr 4 exhibited no catalytic activity (entry 12). A brief screening of counter anions [11] revealed that SbF 6 À and BF 4 À were much worse than NTf 2 À with regard to the reaction yield (entries 13,14). No further improvement was observed when screening at different temperatures (entries 15,16).…”