Gennadiy Ilyashenko

Synthesis of Aminoboronic Acids and Their Applications in Bifunctional Catalysis

Amino acids have been known to catalyze organic reactions for many years, but their boronic acid counterparts are much less well-studied. Although there are a number of useful general approaches to the synthesis of protected aminoboronic acids, many practical challenges remain in the isolation and purification of free aminoboronic acids. Despite these issues, now several different chiral and achiral aminoboronic acids show promise as bifunctional organic catalysts. In this Account, we describe both advances in the synthesis of these aminoboronic acids and some of their underdeveloped potential in catalysis. The first aminoboronic acids that demonstrated catalytic properties, such as 8-quinoline boronic acid, enabled the hydrolysis and etherification of chlorohydrins. More recently, aminoboronic acids have effectively catalyzed direct amide formation. In addition, these catalysts can enable the kinetic resolution of racemic amines during the acylation process. Aminoboronic acids can also function as aldol catalysts, acting through in situ boronate enolate formation in water, and have facilitated tunable asymmetric aldol reactions, acting through the formation of an enamine. On the basis of these examples, we expect that these molecules can catalyze an even wider range of reactions. We anticipate many further discoveries in this area.

Solvent-mediated selective single and double ring-opening of N-tosyl-activated aziridines using benzylamine

An efficient methodology has been developed for the synthesis of a series of new diamine 2 and triamine ligands 3 for application in asymmetric catalysis via selective single or double ring-opening of tosylaziridines 1, which are derived from chiral pool amino acids. The selectivity of the ring-opening reaction is readily controlled by the solvent employed. Thus, in acetonitrile formation of secondary amines 2 occurs via a single ring-opening step, whilst in methanol the reactions proceed to give the tertiary amines 3 via the ring-opening of two aziridine molecules.

Initial rate kinetic studies show an unexpected influence of para-substituents on the catalytic behaviour of manganese complexes of TMTACN in the epoxidation of styrenes with H2O2

Investigations into the efficacy of a range of enantiomerically pure BINOL additives in the epoxidation of styrene substrates with a number of manganese catalysts prepared from the ligand 1,4,7-trimethyl-1,4,7-triazacyclononane, TMTACN, using hydrogen peroxide as the oxidant have revealed that there are fundamental differences in reactivity between apparently similar systems. Whilst no asymmetric induction was obtained in the styrene oxide products formed, the data obtained from initial rate kinetic studies appear to be consistent with a number of different catalytically active species operating, the nature of which are profoundly affected by the starting materials used.

A synthesis of a 1,1′-desymmetrised ferrocene backbone and its facile one-pot double-“click” functionalisation

A one-pot, four-component, copper-catalysed double-“click” functionalisation of a novel 1,1′-desymmetrised ferrocene backbone is reported. Using an array of alkynes and azides, a library of ferrocene compounds was developed, demonstrating the scope of this methodology for its potential application in the assembly of novel materials, ligands or biological sensors.