An Overview of One and Two Carbon Homologation and Homologation-Functional Group Interconversion Reactions in Organic Synthesis

The extension of carbon chains, known as homologation, is one of the most fundamental operations of organic synthesis. One and two-carbon homologation reactions are of immense importance because they can be used for synthesizing members of a homologous series by iterative operations. Homologation reactions produce higher analogues of the same functional group, whereas homologation-functional group interconversion (FGI) generates higher analogues with a change in functionality. This general synthesis strategy may be counted for a number of reasons, such as higher accessibility to the successive homologs, a chance for the introduction of additional functionality, or solely to create a regular series of homologs. The advantages of homologation reactions could be measured by the efficiency, technical simplicity, and regio- and/or stereo-selectivity of the overall operations in a synthetic plan. Homologation reactions constitute powerful and versatile tools for preparative chemistry which uses different concepts underpinning the use of homologating reagents in addition to their applications in organic synthesis. A compilation and comparison of diverse methods available for homologation cum functional group interconversion will empower synthetic chemists to undertake studies that require a series of analogues. In this review, we have categorized and summarized such methods and synthetic applications of one and two-carbon homologation-functionalization of various functional groups in organic synthesis.