Carbon dioxide exits in the atmosphere and is produced by the combustion of fossil fuels, the fermentation of sugars and the respiration of all living organisms. An active goal in organic synthesis is to take this carbon-trapped in a waste product-and re-use it to build useful chemicals. Recent advances in organometallic chemistry and catalysis provide effective means for the chemical transformation of CO 2 and its incorporation into synthetic organic molecules under mild conditions. Such a use of carbon dioxide as a renewable one-carbon (C1) building block in organic synthesis could contribute to a more sustainable use of resources.A more sensible resource management is the prerequisite for the sustainable development of future generations. However, when dealing with the feedstock of the chemical industry, the level of sustainability is still far from satisfactory. Until now, the vast majority of carbon resources are based on crude oil, natural gas and coal. In addition to biomass, CO 2 offers the possibility to create a renewable carbon economy. Since pre-industrial times, the amount of CO 2 has steadily increased and nowadays CO 2 is a component of greenhouse gases, which are primarily responsible for the rise in atmospheric temperature and probably abnormal changes in the global climate. This increase in CO 2 concentration is largely due to the combustion of fossil fuels, which are required to meet the world's energy demand 1 . Obviously, there is an urgent need to control CO 2 emissions and develop efficient carbon capture systems. Although the extensive use of carbon dioxide for chemical production cannot solve this problem alone, CO 2 is a useful one-carbon (C1) building block in organic synthesis due to its abundance, availability, nontoxicity and recyclability. As a result, valorization of CO 2 is currently receiving considerable and ever increasing attention by the scientific community 2-4 . However, activation and utilization of CO 2 is still problematic due to the fact that it is the most oxidized form of carbon, which is also thermodynamically stable and/or kinetically inert in certain desired transformations. Consequently, most of the known studies used highly reactive substrates and/or severe reaction conditions to activate CO 2 , limiting the application of such methods. In particular, the catalytic coupling of CO 2 with energy-rich substrates, such as epoxides and aziridines, to generate polycarbonates/polycarbamates and/or cyclic carbonates/carbamates has drawn significant attention over the past decades. To create C-C bonds with CO 2 , the use of carbon nucleophiles is specifically limited to strong nucleophilic organolithiums and Grignard reagents, as well as phenolates.

Renewable resources and bio-based feedstocks may present a sustainable alternative to petrochemical sources to satisfy modern society's ever-increasing demand for energy and chemicals. However, the conversion processes needed for these future bio-refineries will likely differ from those currently used in the petrochemical industry. Biotechnology and chemocatalysis offer routes for converting biomass into a variety of molecules that can serve as platform chemicals. While a host of technologies can be leveraged for biomass upgrading, condensation reactions are significant because they have the potential to upgrade these bio-derived feedstocks while minimizing the loss of carbon and the generation of by-products. This review surveys both the biological and chemical catalytic routes to producing platform chemicals from renewable sources and describes advances in condensation chemistry and strategies for the conversion of these platform chemicals into fuels and high-value chemicals.

Carbon monoxide was discovered and identified in the 18th century. Since the first applications in industry 80 years ago, academic and industrial laboratories have broadly explored CO's use in chemical reactions. Today organic chemists routinely employ CO in organic chemistry to synthesize all kinds of carbonyl compounds. Despite all these achievements and a century of carbonylation catalysis, many important research questions and challenges remain. Notably, apart from academic developments, industry applies carbonylation reactions with CO on bulk scale. In fact, today the largest applications of homogeneous catalysis (regarding scale) are carbonylation reactions, especially hydroformylations. In addition, the vast majority of acetic acid is produced via carbonylation of methanol (Monsanto or Cativa process). The carbonylation of olefins/alkynes with nucleophiles, such as alcohols and amines, represent another important type of such reactions. In this Account, we discuss our work on various carbonylations of unsaturated compounds and related reactions. Rhodium-catalyzed isomerization and hydroformylation reactions of internal olefins provide straightforward access to higher value aldehydes. Catalytic hydroaminomethylations offer an ideal way to synthesize substituted amines and even heterocycles directly. More recently, our group has also developed so-called alternative metal catalysts based on iridium, ruthenium, and iron. What about the future of carbonylation reactions? CO is already one of the most versatile C1 building blocks for organic synthesis and is widely used in industry. However, because of CO's high toxicity and gaseous nature, organic chemists are often reluctant to apply carbonylations more frequently. In addition, new regulations have recently made the transportation of carbon monoxide more difficult. Hence, researchers will need to develop and more frequently use practical and benign CO-generating reagents. Apart from formates, alcohols, and metal carbonyls, carbon dioxide also offers interesting options. Industrial chemists seek easy to prepare catalysts and patent-free ligands/complexes. In addition, non-noble metal complexes will interest both academic and industrial researchers. The novel Lucite process for methyl methacrylate is an important example of an improved catalyst. This reaction makes use of a specific palladium/bisphosphine catalyst, which led to the successful implementation of the technology. More active and productive catalysts for related carbonylations of less reactive olefins would allow for other large scale applications of this methodology. From an academic point of view, researchers continue to look for selective reactions with more functionalized olefins. Finally, because of the volatility of simple metal carbonyl complexes, carbonylation reactions today remain a domain of homogeneous catalysis. The invention of more stable and recyclable heterogeneous catalysts or metal-free carbonylations (radical carbonylations) will be difficult, but could offer interesting challenge...

Alkene carbonylation reactions are important for the production of value-added bulk and fine chemicals. Nowadays, all industrial carbonylation processes make use of highly toxic and flammable carbon monoxide. In fact, these properties impede the wider use of carbonylation reactions in industry and academia. Hence, performing carbonylations without the use of CO is highly desired and will contribute to the further advancement of sustainable chemistry. Although the use of carbon monoxide surrogates in alkene carbonylation reactions has been reported intermittently in the last 30 years, only recently has this area attracted significant interest. This Minireview summarizes carbonylation reactions of alkenes using different carbon monoxide surrogates.