Stereo- and chemodivergent enantioselective reaction pathways are observed upon treatment of alkylarylketenes and trichloroacetaldehyde (chloral) with N-heterocyclic carbenes, giving selectively either β-lactones (up to 88:12 dr, up to 94 % ee) or α-chloroesters (up to 94 % ee). Either 2-arylsubstitution or an α-branched iPr alkyl substituent within the ketene favours the chlorination pathway, ...

The selective construction of a diverse array of five-membered aromatic heterocycles from common starting materials is an attractive and challenging task. We report here that 5-alkylthio-pyrroles, 4-alkylthiocarbonyl-pyrroles and 2-alkylthio-4-tosyl-furans can be prepared, selectively, in a single operation using the readily available α-formyl ketene dithioacetals as common precursors, through ...

Asymmetric, catalytic reactions of oxocarbenium ions are reported. Simple, chiral urea and thiourea derivatives are shown to catalyze the enantioselective substitution of silyl ketene acetals onto 1-chloroisochromans. A mechanism involving anion binding by the chiral catalyst to generate a reactive oxocarbenium ion is invoked. Catalysts bearing tertiary benzylic amide groups afforded highest en...

A new route to 5-(imidazolidin-2-ylidene)-2-methylsulfanyl-3,5-dihydro-imidazol-4-ones 4a-c using ketene dithioacetal intermediates 3a-c is described. The reactivity of thiohydantoin derivatives 2a-c towards N,N-dimethylformamide diethylacetal (DMF-DEA) was also explored using solvent-free technique under microwave irradiation (mu omega). The (1)H- and (13)C-NMR spectra of some representative p...