Kinetic Rationalization of Nonlinear Effects in Asymmetric Catalytic Cascade Reactions under Curtin-Hammett Conditions

Multicomponent Cyclizative 1,2-Rearrangement Enabled Enantioselective Construction of 2,2-Disubstituted Pyrrolinones

The 1,2-rearrangement reaction is one of the most important approaches to construct carbon-carbon bonds in organic synthesis. However, the development of catalytic asymmetric 1,2-rearrangements is still far from mature and often suffers from problems such as complex substrates, single product structure, and lack of synthetic application. Multicomponent reaction has been recognized as a robust tool for the synthesis of diverse and tunable products from readily available starting material. Conceptionally and practically, the development of multicomponent asymmetric 1,2-rearrangements is highly desirable. In this regard, we report herein a three-component benzilic acid-type rearrangement of 2,3-diketoesters, aromatic amines and aldehydes for the asymmetric construction of synthetically challenging pyrrolinones bearing aza-quaternary stereocenters. To the best of our knowledge, this reaction represents the first example of organocatalyzed multicomponent asymmetric 1,2-rearrangements.

Encapsulation of H4SiW12O40 into an Amide-Functionalized MOF: A Highly Efficient Nanocomposite Catalyst for Oxidative Desulfurization of Diesel Fuel

Production of hydrocarbon fuels containing sulfur in ultralow levels is in high demand and requires the development of novel catalytic systems for oxidative desulfurization (ODS). Herein, a new nanocomposite SiW12@ZSTU-10 catalyst containing H4SiW12O40 (SiW12) encapsulated into a zinc(II) 3D metal-organic framework (MOF) (ZSTU-10) was assembled and characterized. The intricate structure and porosity of ZSTU-10 permit efficient encapsulation of the catalytically active SiW12 cages. The impact of different experimental parameters on the ODS of model oil containing dibenzothiophene as a typical S-based contaminant was evaluated. The SiW12@ZSTU-10 catalyst exhibits remarkable activity with up to 99.8% sulfur removal in 30 min. Kinetic features, trapping tests, and mechanistic studies were also performed. Furthermore, the catalyst offered an outstanding thermal and chemical stability, without apparent leaching and decline in the activity after six cycles. Such an improved catalytic efficiency of SiW12@ZSTU-10 can be assigned to (i) size-matched occupation of the ZSTU-10 pores by SiW12-active species, (ii) prevention of polyoxometalate (POM) leaching from the MOF matrix, (iii) facilitation of the access of S-based substrates to the active sites of SiW12, and (iv) excellent stability and recyclability of the obtained nanocomposite. The preset work widens a family of promising nanocomposite catalysts for improving the desulfurization performance of hybrid POM-MOF catalytic systems.

Cu-Catalyzed Enantioselective Protoboration of 2,3-Disubstituted 1,3-Dienes

A Cu-catalyzed regio- and enantioselective protoboration of 2,3-disubstituted 1,3-dienes is described. The protocol operates under mild conditions and is applicable to symmetrically and unsymmetrically substituted dienes, providing access to homoallylic boronates in consistently high yield, regioselectivity, and enantiomeric ratio. Preliminary investigations point to a complex mechanism.

Molecular Understanding and Practical In Silico Catalyst Design in Computational Organocatalysis and Phase Transfer Catalysis-Challenges and Opportunities

Through the lens of organocatalysis and phase transfer catalysis, we will examine the key components to calculate or predict catalysis-performance metrics, such as turnover frequency and measurement of stereoselectivity, via computational chemistry. The state-of-the-art tools available to calculate potential energy and, consequently, free energy, together with their caveats, will be discussed via examples from the literature. Through various examples from organocatalysis and phase transfer catalysis, we will highlight the challenges related to the mechanism, transition state theory, and solvation involved in translating calculated barriers to the turnover frequency or a metric of stereoselectivity. Examples in the literature that validated their theoretical models will be showcased. Lastly, the relevance and opportunity afforded by machine learning will be discussed.

Mechanistic interpretation of orders in catalyst greater than one

Orders in catalyst greater than one can be attributed to several different reaction mechanisms. Differentiating among these possibilities requires careful analysis of their rate laws, rational experiment design and accurate measurement of the progress of the reactions. We have compiled the most popular mechanisms proposed for reactions with an order in catalyst greater than one and derived their steady-state rate laws. We have analysed the rate laws and proposed experiments to discern between mechanisms. Finally, we have examined 100 case studies that showcase good practices to propose robust mechanisms and to avoid common pitfalls.