Reductive cyclisations of amidines involving aminal radicals

The first general study of aminal radical cyclisations, triggered by reduction of amidines with SmI2, delivers quinazolinones with complete diastereocontrol.

Synthesis of substituted γ- and δ-lactams based on titanocene(iii)-catalysed radical cyclisations of trichloroacetamides

Straightforward synthesis of dehalogenated γ- and δ-lactams based on a Cp2TiCl-catalysed radical cyclisation of trichloroacetamides under mild conditions.

Tuneable radical cyclisations: a tin-free approach towards tricyclic and spirocyclic heterocycles via a common precursor

A novel common precursor approach towards both tricyclic and spirocyclic heterocycles is described. Cyclisations are based on thiyl radical/isocyanide methodology and avoid the use of tin.

Interplay of ortho- with spiro-cyclisation during iminyl radical closures onto arenes and heteroarenes

Sensitised photolyses of ethoxycarbonyl oximes of aromatic and heteroaromatic ketones yielded iminyl radicals, which were characterised by EPR spectroscopy. Iminyls with suitably placed arene or heteroarene acceptors underwent cyclisations yielding phenanthridine-type products from ortho-additions. For benzofuran and benzothiophene acceptors, spiro-cyclisation predominated at low temperatures, but thermodynamic control ensured ortho-products, benzofuro- or benzothieno-isoquinolines, formed at higher temperatures. Estimates by steady-state kinetic EPR established that iminyl radical cyclisations onto aromatics took place about an order of magnitude more slowly than prototypical C-centred radicals. The cyclisation energetics were investigated by DFT computations, which gave insights into factors influencing the two cyclisation modes.