On Scalability, Synthetic Efficiency, and Convergency

Terms like scalability, synthetic efficiency, and convergency are often used by development chemists to qualify the merits of their processes. However, these are often qualitative designations, devoid of any quantitative assessment. We propose some guidelines to support the judicious use of these terms. In particular, we would like to bring to the attention of process chemists the work of J. B. Hendrickson, who─almost 50 years ago─first proposed a meaningful quantitative evaluation of a synthetic plan and defined consistency and convergency in a quantitative way. After a brief analysis of the term scalability, this perspective presents a simplified version of Hendrickson’s ideas and extends it to multicomponent reactions. The metrics proposed herein are very easy to use and should allow chemists to verify the efficiency of their synthetic plan by calculating a consistency index and a convergency index which could complement qualitative descriptors like “efficient process” or “highly convergent synthesis”.