One Sentence Summary: A modular platform for synthesis is demonstrated that makes purified organic compounds autonomously without physical reconfiguration and is driven using a chemical programming language.Abstract: The synthesis of complex organic compounds is largely a manual process that is often incompletely documented. To address these shortcomings, we developed an abstraction that maps commonly reported methodological instructions into discrete steps amenable to automation. These unit operations were implemented in a modular robotic platform using a chemical programming language which formalizes and controls the assembly of the molecules.We validated the concept by directing the automated system to synthesize three pharmaceutical compounds, Nytol, Rufinamide, and Sildenafil, without any human intervention. Yields and purities of products and intermediates were comparable to or better than those achieved manually. The syntheses are captured as digital code that can be published, versioned, and transferred flexibly between platforms with no modification, thereby greatly enhancing reproducibility and reliable access to complex molecules.The automation of chemical synthesis is currently expanding, and this is driven by the availability of digital labware. The field currently encompasses areas as diverse as the design of new reactions (1), chemistry in reactionware (2), reaction monitoring and optimization (3,4), flow chemistry (5) for reaction optimization and scale up, to full automation of the synthesis

The oxidation of the C–H and C=C bonds of hydrocarbons with H2O2 catalyzed by non-heme iron complexes with pentadentate ligands is widely accepted as involving a reactive FeIV=O species such as [(N4Py)FeIV=O]2+ formed by homolytic cleavage of the O–O bond of an FeIII–OOH intermediate (where N4Py is 1,1-bis(pyridin-2-yl)-N,N-bis(pyridin-2-ylmethyl)methanamine). We show here that at low H2O2 concentrations the FeIV=O species formed is detectable in methanol. Furthermore, we show that the decomposition of H2O2 to water and O2 is an important competing pathway that limits efficiency in the terminal oxidant and indeed dominates reactivity except where only sub-/near-stoichiometric amounts of H2O2 are present. Although independently prepared [(N4Py)FeIV=O]2+ oxidizes stoichiometric H2O2 rapidly, the rate of formation of FeIV=O from the FeIII–OOH intermediate is too low to account for the rate of H2O2 decomposition observed under catalytic conditions. Indeed, with excess H2O2, disproportionation to O2 and H2O is due to reaction with the FeIII–OOH intermediate and thereby prevents formation of the FeIV=O species. These data rationalize that the activity of these catalysts with respect to hydrocarbon/alkene oxidation is maximized by maintaining sub-/near-stoichiometric steady-state concentrations of H2O2, which ensure that the rate of the H2O2 oxidation by the FeIII–OOH intermediate is less than the rate of the O–O bond homolysis and the subsequent reaction of the FeIV=O species with a substrate.

Although the automatic synthesis of molecules has been established, each reaction class uses bespoke hardware. This means that the connection of multi-step syntheses in a single machine to run many different protocols and reactions is not possible, as manual intervention is required. Here we show how the Chemputer synthesis robot can be programmed to perform many different reactions, including solid-phase peptide synthesis, iterative cross-coupling and accessing reactive, unstable diazirines in a single, unified system with high yields and purity. Developing universal and modular hardware that can be automated using one software system makes a wide variety of batch chemistry accessible. This is shown by our system, which performed around 8,500 operations while reusing only 22 distinct steps in 10 unique modules, with the code able to access 17 different reactions. We also demonstrate a complex convergent robotic synthesis of a peptide reacted with a diazirine-a process requiring 12 synthetic steps.The synthesis of organic small molecules is still largely performed by hand in the laboratory, a paradigm that has barely changed in decades, despite predictions of imminent change 1,2 . The issue is that organic synthesis is not only labour intensive but also highly specialized, requiring years of training. Given these characteristics of organic synthesis, the automation of small-molecule synthesis has the potential to improve reproducibility and accessibility. However, the lack of a universal approach means that current technologies are highly specialized and focus on specific niches, for example, for the automated synthesis of oligopeptides 3 , oligonucleotides 4 , oligosaccharides 5 and, recently, with MIDA boronate building blocks 6 . All these approaches are based on the successive iteration of a small number of robust reactions; hence, they are not generally programmable nor are the unit operations reusable. Such systems are ideal for process intensification but require extensive method development and specific hardware 7 . These limitations have been partly addressed by the development of reconfigurable flow systems addressing a wider range of chemistries 8,9 . What is needed is a paradigm that not only captures the expertise and numerous hours spent discovering and optimizing batch reactions but also is amenable to the development of an overarching ontology that allows universality. Previously, the concept of the Chemputer, a programmable batch synthesis robot, was designed and developed to demonstrate the proof of principle for a general approach to the synthesis of any organic molecule, whereby a range of different molecules could be automatically synthesized on the same hardware 10 . However, the ability to

Reaction bifurcation processes are often encountered in the oxidation of substrates by enzymes and generally lead to a mixture of products. One particular bifurcation process that is common in biology relates to electron transfer versus oxygen atom transfer by high-valent iron(IV)-oxo complexes, which nature uses for the oxidation of metabolites and drugs. In biomimicry and bioremediation, an important reaction relates to the detoxification of ClO in water, which can lead to a mixture of products through bifurcated reactions. Herein we report the first three water-soluble non-heme iron(II) complexes that can generate chlorine dioxide from chlorite at ambient temperature and physiological pH. These complexes are highly active oxygenation oxidants and convert ClO into either ClO or ClO¯ via high-valent iron(IV)-oxo intermediates. We characterize the short-lived iron(IV)-oxo species and establish rate constants for the bifurcation mechanism leading to ClO and ClO products. We show that the ligand architecture of the metal center plays a dominant role by lowering the reduction potential of the metal center. Our experiments are supported by computational modeling, and a predictive valence bond model highlights the various factors relating to the substrate and oxidant that determine the bifurcation pathway and explains the origins of the product distributions. Our combined kinetic, spectroscopic, and computational studies reveal the key components necessary for the future development of efficient chlorite oxidation catalysts.