Formal Bimolecular [2 + 2 + 2] Cycloaddition Strategy for the Synthesis of Pyridines: Intramolecular Propargylic Ene Reaction/Aza Diels-Alder Reaction Cascades.

Two methods for the synthesis of multisubstituted pyridines are described. In each strategy, a highly reactive vinylallene is generated via an intramolecular propargylic ene reaction in the presence of an azadienophile. Reactions employing ethyl N-(tosyl)iminoacetate furnish an intermediate that undergoes elimination and isomerization upon the addition of DBU.

Aza Diels-Alder Reactions of Nitriles, N,N-Dimethylhydrazones, and Oximino Ethers. Application in Formal [2 + 2 + 2] Cycloadditions for the Synthesis of Pyridines.

Metal-free, formal [2 + 2 + 2] cycloaddition strategies for the synthesis of polycyclic pyridine derivatives are described. The overall transformation proceeds via a two-stage pericyclic cascade mechanism. In the first step, an intramolecular propargylic ene reaction generates a vinylallene that is necessarily locked in the s-cis conformation.

Reactions of oxetan-3-tert-butylsulfinimine for the preparation of substituted 3-aminooxetanes.

The oxetane ring is useful in drug discovery as a bioisostere for both the geminal dimethyl group and the carbonyl group. A convenient, straightforward approach to access structurally diverse 3-aminooxetanes through the reactivity of oxetan-3-tert-butylsulfinimine and the corresponding sulfinylaziridine is described.