The metal-catalyzed rearrangement of aldoximes into primary amides is a completely atom economical synthetic method for the preparation of one of the most important functional groups in chemistry. There have been several reports of various metals successfully catalyzing this reaction, however, there are conflicting views as to the mechanism involved. Herein we report new experimental evidence to support the mechanism and whether this is universal to all catalysts reported or metal specific. We also describe our further studies into the mechanism of the nickel-catalyzed acylation of amines with aldoximes.Keywords: aldoximes; amides; mechanism; rearrangement The efficient synthesis of amide bonds is of great importance in both research and industrial chemistry due to the prevalence of this group in biologically active molecules, agrochemicals and polymer chemistry.[1] The metal-catalyzed rearrangement of aldoximes into primary amides offers a completely atom economical synthesis of this important chemical moiety. This reaction can also be run from the aldehyde oxidation level with the formation of the aldoxime occurring in situ when mixed with hydroxylamine.The first catalytic conditions for this rearrangement were reported by Chang and co-workers in 2003. [2] They found that Wilkinsons complex (at a catalyst loading of 5 mol%) efficiently catalyzed the conversion of a range of aldoximes into their corresponding primary amides at a temperature of 150 8C. Following this initial publication, reports of iridium, [3] ruthenium [4] and palladium [5] catalysts performing the rearrangement appeared in the literature detailing procedures at lower temperatures.Research efforts have more recently been focussed towards finding lower cost metal catalysts and procedures that can be run in the absence of undesirable organic solvents. This is highlighted in the work reported by Mizuno, [6] Nolan [7] and our own group [8,9] (Scheme 1). Mizuno and co-workers reported a reusable supported rhodium hydroxide catalyst to work in this reaction in aqueous conditions, followed later by Nolan and co-workers reporting a gold/silver co-catalyzed reaction proceeding under solvent-free conditions. We have shown that relatively inexpensive copper, zinc and indium salts are as effective as the precious transition metals at catalyzing aldoxime rearrangements. It has been proposed that the mechanism for this metal-catalyzed rearrangement proceeds via a discrete nitrile intermediate which is formed through dehydration of a coordinated oxime species. This is supported by the frequent detection of a small quantity of nitrile by-product on analysis of the crude reaction Scheme 1. Recently reported conditions for aldoxime rearrangements into primary amides.

We report the straight forward synthesis of a series of arene-borazine hybrids (BN-PAHs) called borazatruxenes; the DFT, solid state and solution characterisation are reported along with the separation and chiroptical studies of four optical isomers.

No abstract

No abstract

No abstract