An Efficient and Diastereoselective Intramolecular 1,3-Dipolar Cycloaddition of Cyclic Azomethine Ylides and Nitrones

[3 + 2]-Dipolar Cycloaddition of Aldehyde-Tethered Alkynamides and Trimethylsilyl Amino Esters: A Gateway to Uniquely Functionalized Polycyclic N-Heterocycles via Post-Ugi Functionalization

An efficient method for the generation of uniquely functionalized pyrrolo-pyrrolizinones, pyrido-pyrrolizinones, and azepino-pyrrolizinones via [3 + 2]-dipolar cycloaddition is described. The method involves the synthesis of tethered alkynamides using Ugi condensation and oxidation that were subsequently subjected to a dipolar cycloaddition reaction with trimethylsilyl amino esters. Further transformations to demonstrate the utility of these scaffolds were also investigated.

A New Synthetic Route to Polyhydrogenated Pyrrolo[3,4-b]pyrroles by the Domino Reaction of 3-Bromopyrrole-2,5-Diones with Aminocrotonic Acid Esters

A new synthetic approach to polyfunctional hexahydropyrrolo[3,4-b]pyrroles was developed based on cyclization of N-arylbromomaleimides with aminocrotonic acid esters. A highly chemo- and stereoselective reaction is a Hantzsch-type domino process, involving the steps of initial nucleophilic C-addition or substitution and subsequent intramolecular nucleophilic addition without recyclyzation of imide cycle.

Ethyl 1-benzyl-1,2,3,3a,4,10b-hexa-hydro-pyrrolo-[2',3':3,4]pyrrolo-[1,2-a]benzimidazole-2-carboxyl-ate

The title mol­ecule, C₂₂H₂₃N₃O₂, was obtained via an intra­molecular cyclo­addition of an azomethine ylide and an alkene tethered by a benzimidazole unit. The benzoimidazole unit is essentially planar, with an r.m.s. deviation of 0.0087 Å from the nine constituent atoms. It has a cis fusion of the two pyrrolidine rings as well as a cis ester appendage. The two pyrrolidine rings rings have envelope conformations. The crystal packing is stabilized by aromatic π–π stacking of parallel benzimidazole ring systems, with a centroid-to-centroid distance of 3.518 (6) Å. Weak inter­molecular C—H⋯O contacts may also play a role in the stability of the packing.