Search

Heterogeneous catalysis plays an indispensable role in chemical production and energy conversion. Incorporation of transition metals into metal oxides and zeolites is a common strategy to fine-tune the activity and selectivity of the resulting solid catalysts, as either the active center or promotor. Studying the underlying mechanism is however challenging. Decorating the metal-oxo clusters with transition metals in metal-organic frameworks (MOFs) via postsynthetic modification offers a rational approach to construct well-defined structural models for better understanding of the reaction mechanism. Therefore, it is important to expand the materials scope beyond the currently widely studied zirconium MOFs consisting of Zr6 nodes. In this work, we report the design and synthesis of a new (4,12)-connected Zr-MOF with ith topology that consists of rare Zr9 nodes. FeIII was further incorporated onto the Zr9 nodes of the framework, and the resulting MOF material exhibits significantly enhanced activity and selectivity toward the photocatalytic oxidation of toluene. This work demonstrates a delicate ligand design strategy to control the nuclearity of Zr-oxo clusters, which further dictates the number and binding sites of transition metals and the overall photocatalytic activity toward C-H activation. Our work paves the way for future exploration of the structure-activity study of catalysts using MOFs as the model system.

The oxidation of N-cyclopropyl-N-methylaniline by the single electron transfer enzyme horseradish peroxidase is investigated.

Studies were conducted to identify a new breed of complexes obtained from monoanionic aromatic diol ligands by using substituted binaphthol, R2BINOH2, as a chiral auxiliary. A range of aromatic diols were examined to establish the influence of the chelate ring size and steric attributes of phenol substituents on the strength of the hydrogen bond. The strength of the hydrogen bond correlates directly to the ring size. The binding constant is methodically lowered by around 1 order of magnitude, upon enhancing the ring size by one carbon.

A range of 1,1'-bi-2-naphthol (H2BINO) derivatives react with WCl6 to generate W(R2BINO)3-nCl2n derivatives. The extent of R2BINO substitution on a WCl6 template is controlled by the steric demands of the substituent in the 3,3-position. The W(Me2BINO)2Cl2 product preferentially forms a trans-(R*,R*) complex. Two diastereomers of W(BINO)3 are isolated, with the delta*-(S*,S*,S*) and delta*-(S*,S*,R*) complexes being favored. Studies of norborene polymerization using these asymmetric chelate complexes as precatalysts generated little variation in product stereochemistry.

The facial selectivity in the dimethyldioxirane (DMDO) epoxidation of carbohydrate-based oxepines derived from glucose, galactose and mannose is determined by product analysis and density functional theory calculations. The factors obtained have predicted the facial selectivity in the DMDO-epoxidation of cyclic enol ethers.

A retro-Cope mechanism for the formation of the N-hydroxylamide esters by reaction of dimethyl squarate is introduced as the result of a comparative reactive study. The preliminary iron (III) binding study of the hydroxamic acid demonstrates binding of iron to amides and reflects no effect on the esters.

Research into the enzymatic N-dealkylation of cyclopropylamines is presented.

The polymer PEDOT+ mediates a Nazarov-like cyclization of dienones, in an heterogeneous system and in hydrocarbon solvents. The polymer-mediated reactions show clear differences in product formation when compared to the same reaction with tosic acid, or when compared to reports in the literature. Comparable or improved yields are observed, as well as the ability to give a Nazarov product in cases where treatment with acid fails to give cyclization, or leads to an undesirable rearrangement. In addition, the ability to recycle the polymer makes this a potentially useful protocol for an important organic chemical reaction. [ABSTRACT FROM AUTHOR]

Both poly(3,4-ethylenedioxythiophene) and poly(pyrrole) mediate a pinacol rearrangement of 1,2-diols. The yields of ketone or aldehyde products are comparable to those observed for treatment with mineral acids or Lewis acids. The advantage of this protocol is a two-phase reaction medium in hydrocarbon solvents that allows facile recovery of the products by simple filtration of the polymer and removal of solvents. Both the polymer and the hydrocarbon solvent may be recovered and used in subsequent reactions. [ABSTRACT FROM AUTHOR]

A procedure for the synthesis of oxazolidinone and tosyl enamines is reported. Alkynoyl oxazolidinones and tosyl imides undergo reaction to form enamines in the presence of catalytic amounts of tertiary amines. The data suggest that an amide anion is formed during the reaction, which undergoes conjugate addition to form the final product. [ABSTRACT FROM AUTHOR]