An Organocatalytic Approach to the Synthesis of Six-Membered Heterocycles

In the last few years, the new era of organocatalysis opened up an effective and efficient way to high yielding metal free, enantio- and diastereoselective reactions leading to six-membered heterocycles. This review provides an overview of the current achievements in the organocatalytic synthesis of these crucial building blocks. Ranging from hetero-Diels-Alder to cycloadditions, from one step cyclizations to cascade reactions, recent results offer new powerful tools to obtain six membered heterocycles with facile procedures in high yields and stereoselection, often leading to many new stereogenic centres in a single reaction. The total syntheses of natural products having heterocyclic ring formation as crucial stage, are also reported. When available, alternative supported organocatalysts have been examined.