Recent Advances in the Synthesis of Spiro-β-Lactams and Spiro-δ-Lactams

Spirocyclic molecules are widely recognized for their complex three-dimensional features and structural rigidity. Among this class of molecules, the spiro-lactams subclass stands out, being extensively explored due to its bioactivity and utility in a variety of scientific fields such as drug design and organic synthesis. Given the recognition of spirocyclic lactams' broad potential, several efforts have been engaged on the pursuit of new synthetic strategies towards these molecules. The present review gathers advances on the synthesis of both spiro-beta-lactams (spiroazetidin-2-ones) and spiro-delta-lactams (spiropiperidon-2-ones) reported since 2015. The work is divided into two distinct parts, each one dedicated to one of these types of spiro-lactam, with the approach used for building the spirocyclic system being extensively discussed, according to the method's scope, efficiency, selectivity, and reaction mechanism. 1. Introduction 2. Spiro-beta-Lactams 2.1. beta-Lactam Ring Synthesis 2.2. Non-beta-Lactam Ring Synthesis 2.3. beta-Lactam and Non-beta-Lactam Ring Synthesis 3. Spiro-delta-Lactams 3.1. delta-Lactam Ring Synthesis 3.2. Non-delta-Lactam Ring Synthesis 3.3. delta-Lactam and Non-delta-lactam Ring Synthesis 4. Conclusion