On Using Tree Analysis to Quantify the Material, Input Energy, and Cost Throughput Efficiencies of Simple and Complex Synthesis Plans and Networks: Towards a Blueprint for Quantitative Total Synthesis and Green Chemistry

Reaction Optimization for Greener Chemistry with a Comprehensive Spreadsheet Tool

Green chemistry places an emphasis on safer chemicals, waste reduction, and efficiency. Processes should be optimized with green chemistry at the forefront of decision making, embedded into research at the earliest stage. To assist in this endeavor, we present a spreadsheet that can be used to interpret reaction kinetics via Variable Time Normalization Analysis (VTNA), understand solvent effects with linear solvation energy relationships (LSER), and calculate solvent greenness. With this information, new reaction conditions can be explored in silico, calculating product conversions and green chemistry metrics prior to experiments. The application of this tool was validated with literature case studies. Reaction performance was predicted and then confirmed experimentally for examples of aza-Michael addition, Michael addition, and an amidation. The combined analytical package presented herein permits a thorough examination of chemical reactions, so that the variables that control reaction chemistry can be understood, optimized, and made greener for research and education purposes.

Green Chemistry Metrics, A Review

Attending both the United Nations Decade of Education for Sustainable Development (2005–2014) and the United Nations 2030 Agenda for Sustainable Development, this review is presented, bearing in mind that green chemistry is essential to contribute to sustainability. This work has compiled all the information relating to green chemistry metrics, so that stakeholders can select an appropriate model, under the Green Chemistry Protocol, to evaluate how much green is a process. The review was organized considering the following convenient sections: the mass valuation, the recognition of the human health and environmental impact, metrics using computational programs (software and spreadsheets), and finally global metrics. This review was developed by consulting the principal databases, since the appearance of the first green chemistry textbook in 1998. A massive number of references were attained involving the keywords proposed below, with six languages observed, highlighted by the English language. It is important to emphasize that the 12 Principles of Green Chemistry are conceptual and offer little quantitative information. In addition, almost all the reported metric green propositions do not consider the 12 principles and few papers offer how to obtain an appropriate evaluation about the greenness of a research. In this sense, it is convenient to note that only in the Spanish literature are there two metrics that consider all the principles. Finally, to our knowledge, and after a deep search in the literature, it is the first review that covers the different features of green chemistry: mass, environment/human health. and in some cases, the use of computational programs.

Chemical data intelligence for sustainable chemistry

This study highlights new opportunities for optimal reaction route selection from large chemical databases brought about by the rapid digitalisation of chemical data. The chemical industry requires a transformation towards more sustainable practices, eliminating its dependencies on fossil fuels and limiting its impact on the environment. However, identifying more sustainable process alternatives is, at present, a cumbersome, manual, iterative process, based on chemical intuition and modelling. We give a perspective on methods for automated discovery and assessment of competitive sustainable reaction routes based on renewable or waste feedstocks. Three key areas of transition are outlined and reviewed based on their state-of-the-art as well as bottlenecks: (i) data, (ii) evaluation metrics, and (iii) decision-making. We elucidate their synergies and interfaces since only together these areas can bring about the most benefit. The field of chemical data intelligence offers the opportunity to identify the inherently more sustainable reaction pathways and to identify opportunities for a circular chemical economy. Our review shows that at present the field of data brings about most bottlenecks, such as data completion and data linkage, but also offers the principal opportunity for advancement.

Mechanochemical Thiocyanation of Aryl Compounds via C-H Functionalization

Aryl thiocyanate compounds are important building blocks for the synthesis of bioactive compounds and intermediates for several functional groups. Reported thiocyanation reactions via C-H functionalization have limited substrate scope and low RME. The ball-milling method reported here uses ammonium persulfate and ammonium thiocyanate as reagents and silica as a grinding auxiliary. It afforded aryl thiocyanates with moderate to excellent yields for a wide variety of aryl compounds (36 examples, 8-96% yield), such as anilines, phenols, anisoles, thioanisole, and indole, thus tolerating substrates with sensitive functional groups. New products such as benzo[d][1,3]oxathiol-2-ones were obtained with C-4 substituted phenols. Thus, to our knowledge, we report, for the first time, aryl thiocyanation reaction by ball-milling at room temperature and solvent-free conditions, with short reaction times and no workup. Analysis of several mass-based green metrics indicates that it is an efficient greener method.

Green Chemistry Metrics with Special Reference to Green Analytical Chemistry

The concept of green chemistry is widely recognized in chemical laboratories. To properly measure an environmental impact of chemical processes, dedicated assessment tools are required. This paper summarizes the current state of knowledge in the field of development of green chemistry and green analytical chemistry metrics. The diverse methods used for evaluation of the greenness of organic synthesis, such as eco-footprint, E-Factor, EATOS, and Eco-Scale are described. Both the well-established and recently developed green analytical chemistry metrics, including NEMI labeling and analytical Eco-scale, are presented. Additionally, this paper focuses on the possibility of the use of multivariate statistics in evaluation of environmental impact of analytical procedures. All the above metrics are compared and discussed in terms of their advantages and disadvantages. The current needs and future perspectives in green chemistry metrics are also discussed.

Designing Safer and Greener Antibiotics

Since the production of the first pharmaceutically active molecules at the beginning of the 1900s, drug molecules and their metabolites have been observed in the environment in significant concentrations. In this review, the persistence of antibiotics in the environment and their associated effects on ecosystems, bacterial resistance and health effects will be examined. Solutions to these problems will also be discussed, including the pharmaceutical industries input, green chemistry, computer modeling and representative ionic liquid research.

Sustainable chemistry metrics

Green chemistry has developed mathematical parameters to describe the sustainability of chemical reactions and processes, in order to quantify their environmental impact. These parameters are related to mass and energy magnitudes, and enable analyses and numerical diagnoses of chemical reactions. The environmental impact factor (E factor), atom economy, and reaction mass efficiency have been the most influential metrics, and they are interconnected by mathematical equations. The ecodesign concept must also be considered for complex industrial syntheses, as a part of the sustainability of manufacturing processes. The aim of this Concept article is to identify the main parameters for evaluating undesirable environmental consequences.