Mechanochemical synthesis of aromatic ketones: pyrylium tetrafluoroborate mediated deaminative arylation of amides

A new method has been introduced that is able to tackle the complexities of N-C(O) activation in amide moieties through utilization of pyrylium tetrafluoroborate in a mechanochemical setting, where amide bonds undergo activation and subsequent conversion to biaryl ketones. Due to the employment of a mechanochemical setting, the reaction conforms to green chemistry principles, offering an environmentally friendly approach to traditional amide derivatization techniques that rely on transition metals to achieve further functionalization.

Effective and sustainable depolymerization of Nylon 66 - a transamidation for the complete recycling of polyamides

The transamidation of polyamides with short primary amides is reported as an effective recycling technique. This novel depolymerization method is robust and only utilizes cheap and renewable reagents. The process requires a Nb2O5 catalyst, assisted by NH3, and operates at relatively mild reaction conditions (i.e. 200 °C and 3 bar NH3).

Chelating Picolinaldehyde Hydrazone Amides as Protecting Groups for Carboxylic Acids: Orthogonal Reactivities of Hydrazone Amides and Esters in Hydrolysis

We report a chelating hydrazone amide as a protecting group for carboxylic acids. Unlike most esters, 2-picolinaldehyde hydrazone amides are stable under acidic or basic hydrolytic conditions. However, hydrazone amides can be easily converted to the corresponding carboxylic acids via Ni-mediated hydrolysis. Orthogonal reactivities of the hydrazone amides and representative protecting groups were verified by control experiments and peptide synthesis, demonstrating that chelating hydrazone amides are highly useful protecting groups.

Adjustment of W-O-Zr Boundaries Boosts Efficient Nitrilation of Dimethyl Adipate with Ammonia on WOx/ZrO2 Catalysts

In this study, a tungstated zirconia (WO_x/ZrO₂) catalyst was developed for the continuous synthesis of adiponitrile (ADN) by gas-phase nitrilation of dimethyl adipate (DMA) with NH₃. The highest TOF_ADN could be reached on WO_x/ZrO₂ bearing ∼1D WO_x species (highly dispersed and discontinuous status) at the surface, which, however, delivered the poorest selectivity toward nitrilation (S_ADN+MCP). In comparison, both efficient and selective transformation of DMA to ADN was achieved by fabricating WO_x/ZrO₂ with continuously distributed oligomeric WO_x species (∼2D) at the surface, either by varying the dosage of the W-reagent in the preparation of WO_x(m)/ZrO₂ or by doping a proper amount of the Mn element into WO_x(5.0)/ZrO₂, bearing WO₃ NPs. Furthermore, the in situ diffuse reflectance infrared Fourier transform spectroscopy investigations of both independent and competitive adsorptions of ester functionality and NH₃ over W-O-Zr, W-O-W, and Zr-O-Zr boundaries at the surface clarified the synergistic effect of these species in the activation of DMA/NH₃ and thereby nitrilation.

Hydrolysis of Acetamide on Low-Index CeO2 Surfaces: Ceria as a Deamidation and General De-esterification Catalyst

Using DFT calculations and acetamide as the main example, we show that ceria is a potential catalyst for the hydrolysis of amide and similar bonds. The overall reaction is endergonic in the gas phase, yielding acetic acid and ammonia, but is slightly exergonic in the aqueous phase, which facilitates ionization of the products (CH₃COO^– and NH₄⁺). Neighboring Ce and O sites on the CeO₂(111), (110), and (100) facets are conducive to the formation of an activated metastable tetrahedral intermediate (TI) complex, followed by C–N bond scission. With van der Waals and solvation effects taken into account, the overall reaction energetics is found to be most favorable on the (111) facet as desorption of acetic acid is much more uphill energetically on (110) and (100). We further suggest that the Ce–O–Ce sites on ceria surfaces can activate X(=Y)–Z type bonds in amides, amidines, and carboxylate and phosphate esters, among many others that we term “generalized esters”. A Brønsted-Evans–Polanyi relationship is identified correlating the stability of the transition and final states of the X–Z generalized ester bond scission. A simple descriptor (ΣΔχ) based on the electronegativity of the atoms that constitute the bond (X, Y, Z) versus those of the catalytic site (O, Ce, Ce) captures the trend in the stability of the transition state of generalized ester bond scission and suggests a direction for modifying ceria for targeting specific organic substrates.

Synthesis of adiponitrile from dimethyl adipate and ammonia in the vapor-phase over niobium oxide

An environmentally benign route leading to adiponitrile (ADN), a nylon-6,6 intermediate, was achieved by direct vapor-phase nitrilation of dimethyl adipate (DMA) with ammonia (NH3) in a fixed-bed reactor.