No abstract

Research progress is often promoted by unexpected results that open the way to new scenarios. In this communication, an unprecedented condensation of arylacetic acids and isocyanides and the unusual base-mediated rearrangement of the resulting products to give two novel classes of polysubstituted pyrrolones and pyrrolidinediones are reported.

Enantiomerically pure 4,5-dihydro-1H-benzo[c]azepines with three contiguous stereogenic centers have been assembled by convergent strategy with a good control of diastereoselectivity. The two steps are as follows: an asymmetric organocatalytic Mannich reaction performed on Boc-imines of o-(azidomethyl)benzaldehydes, followed by a one-pot Staudinger/aza-Wittig/Ugi-Joullié sequence. The latter reaction represents one of the first examples of diastereoselective Ugi three-component reaction on a seven-membered cyclic imine. The o-azidomethylbenzaldehydes have been synthesized employing a simple and efficient chemoenzymatic strategy from commercially available building blocks.

α-Azido aldehydes can be employed in Passerini reactions with isocyanides and various propiolic acids to afford the three-component adducts in moderate to good yields. These compounds undergo a straightforward azide-alkyne dipolar cycloaddition to furnish triazolo-fused dihydrooxazinones.