We report on how to quantify the binding affinity between a nanoparticle and chemical functional group using various experimental methods such as cantilever assay, PeakForce quantitative nanomechanical property mapping, and lateral force microscopy. For the immobilization of Au nanoparticles (AuNPs) onto a microscale silicon substrate, we have considered two different chemical functional molecules of amine and catecholamine (dopamine was used here). It is revealed that catecholamine-modified surface is more effective for the functionalization of AuNPs onto the surface, which is compared with the amine-modified surface from our various experiments. The dimensionless parameter (i.e., ratio of binding affinity) introduced in this work from such experiments is useful in quantitatively depicting such binding affinity, indicating that the binding affinity and stability between AuNPs and catecholamine is approximately 1.5 times stronger than that of amine. Our study sheds light on the experiment-based quantitative characterization of the binding affinity between nanomaterial and chemical groups, which will eventually provide an insight into how to effectively design the functional material using chemical groups.
Selective catalytic synthesis of Z-olefins has been challenging. Here we describe a method to produce 1,2-disubstituted olefins in high Z selectivity via reductive cross-coupling of alkyl halides with terminal arylalkynes . The method employs inexpensive and non-toxic catalyst (iron(II) bromide) and reductant (zinc). The substrate scope encompasses primary, secondary, and tertiary alkyl halides, and the reaction tolerates a large number of functional groups. The utility of the method is demonstrated in the synthesis of several pharmaceutically relevant molecules. Mechanistic study suggests that the reaction proceeds through an iron-catalyzed anti-selective carbozincation pathway.
Alkene hydrosilylation, the addition of a silicon hydride (Si-H) across a carbon-carbon double bond, is one of the largest-scale industrial applications of homogeneous catalysis and is used in the commercial production of numerous consumer goods. For decades, precious metals, principally compounds of platinum and rhodium, have been used as catalysts for this reaction class. Despite their widespread application, limitations such as high and volatile catalyst costs and competing side reactions have persisted. Here, we report that well-characterized molecular iron coordination compounds promote the selective anti-Markovnikov addition of sterically hindered, tertiary silanes to alkenes under mild conditions. These Earth-abundant base-metal catalysts, coordinated by optimized bis(imino)pyridine ligands, show promise for industrial application.
An investigation of the intramolecular cyclopropanation reactions of α-diazo-β-ketonitriles is reported. These studies reveal that α-diazo-β-ketonitriles exhibit unique reactivity in their ability to undergo arene cyclopropanation reactions; other similar acceptor-acceptor-substituted diazo substrates instead produce mixtures of C-H insertion and dimerization products. α-Diazo-β-ketonitriles also undergo highly efficient intramolecular cyclopropanation of tri- and tetrasubstituted alkenes. In addition, the α-cyano-α-ketocyclopropane products are demonstrated to serve as substrates for SN2, SN2', and aldehyde cycloaddition reactions.
A simple and efficient Ru-catalyzed conjugate addition reaction of arylboronic acids to alpha,beta-unsaturated ketones under neutral conditions without any additional ligands has been developed. This Ru(II)-catalytic system fulfilled both the inhibition of the beta-hydride elimination in the catalytic cycle, and minimized the protonolysis of arylboronic acids.
Nitroolefin is a common and versatile reagent, synthesis of which from olefin is generally limited by the formation of mixture of cis- and trans- compounds. Here we report that silver nitrite (AgNO2) along with TEMPO can promote the regio- and stereoselective nitration of a broad range of olefins. This work discloses a new and efficient approach wherein starting from olefin, nitroalkane radical formation and subsequent transformations lead to the desired nitroolefin in a stereoselective manner.
A ‘Cu'te couple: A synthetically useful protocol for the preparation of N-alkynylated sulfoximines (yne sulfoximines) has been developed. The method involves a mild copper-catalyzed oxidative cross-coupling of NH-sulfoximines and terminal alkynes. The corresponding N-acyl sulfoximines were also obtained selectively after acid-catalyzed hydrolysis of the yne sulfoximines.
An efficient method for the synthesis of long-chain α,ω-diamino acids, starting from natural α-amino acids, has been developed. The long-chain skeleton has been generated through condensation between a protected aldehyde, derived from L-aspartic acid, and an ylide obtained from an ω-hydroxy-alkyl phosphonium salt. After conversion of the ω-hydroxy group into an amine, catalytic hydrogenation produced the N,N'-protected α,ω-diamino acid. The present route to α,ω-diamino acids allows the modulation of the chain length depending on the length of the ylide used for the Wittig olefination reaction.
Olefin metathesis catalysts for controlling the formation of trisubstituted macrocyclic Z alkenes have been developed. The most effective complexes are Mo alkylidenes with a pentafluorophenylimido group and two large aryloxide ligands. The macrocyclic lactone precursor to anticancer agents epothilones B and D is obtained in 73 % yield and 91 % Z selectivity in less than 6 hours at room temperature.
A novel palladium-catalyzed highly selective vinylation reaction for direct synthesis of allylic amines from styrenes and aminals has been established. The ability of this method was also demonstrated in one-pot manner for the rapid synthesis of Cinnarizine from aldehydes, amines and simple alkenes. Mechanistic studies suggest the reaction proceeds through a valuable cyclometalated Pd(II) complex generated by the oxidative addition of Pd(0) to aminal.