Mechanistic Investigation into the Acetate-Initiated Catalytic Trimerization of Aliphatic Isocyanates: A Bicyclic Ride.

The acetate-initiated aliphatic isocyanate trimerization to isocyanurate was investigated by state-of-the-art analytical and computational methods. Although the common cyclotrimerization mechanism assumes the consecutive addition of three equivalents of isocyanate to acetate prior to product formation, we found that the underlying mechanism is more complex. In this work, we demonstrate that the product, in fact, is formed via the connection of two unexpected catalytic cycles, with acetate being only the precatalyst. The initial discovery of a precatalyst activation by quantum chemical computations and the resulting first catalysis cycle were corroborated by mass spectrometric and NMR experiments, thereby additionally revealing a catalyst migration to the second catalytic cycle. These results were further confirmed by computations, completing the full mechanistic understanding of this catalytic system. Identification of a side product with undesired properties for final coating applications allows for process optimization in the chemical industry.

Identifying high-performance catalytic conditions for carbon dioxide reduction to dimethoxymethane by multivariate modelling.

In times of a warming climate due to excessive carbon dioxide production, catalytic conversion of carbon dioxide to formaldehyde is not only a process of great industrial interest, but it could also serve as a means for meeting our climate goals. Currently, formaldehyde is produced in an energetically unfavourable and atom-inefficient process. A much needed solution remains academically challenging. Here we present an algorithmic workflow to improve the ruthenium-catalysed transformation of carbon dioxide to the formaldehyde derivative dimethoxymethane. Catalytic processes are typically optimised by comprehensive screening of catalysts, substrates, reaction parameters and additives to enhance activity and selectivity. The common problem of the multidimensionality of the parameter space, leading to only incremental improvement in laborious physical investigations, was overcome by combining elements from machine learning, optimisation and experimental design, tripling the turnover number of 786 to 2761. The optimised conditions were then used in a new reaction setup tailored to the process parameters leading to a turnover number of 3874, exceeding by far those of known processes.

Selective Ruthenium-Catalyzed Transformation of Carbon Dioxide: An Alternative Approach toward Formaldehyde.

Formaldehyde is an important precursor to numerous industrial processes and is produced in multimillion ton scale every year by catalytic oxidation of methanol in an energetically unfavorable and atom-inefficient industrial process. In this work, we present a highly selective one-step synthesis of a formaldehyde derivative starting from carbon dioxide and hydrogen gas utilizing a homogeneous ruthenium catalyst. Here, formaldehyde is obtained as dimethoxymethane, its dimethyl acetal, by selective reduction of carbon dioxide at moderate temperatures (90 °C) and partial pressures (90 bar H2/20 bar CO2) in the presence of methanol. Besides the desired product, only methyl formate is formed, which can be transformed to dimethoxymethane in a consecutive catalytic step. By comprehensive screening of the catalytic system, maximum turnover numbers of 786 for dimethoxymethane and 1290 for methyl formate were achieved with remarkable selectivities of over 90% for dimethoxymethane.