No abstract

α-Functionalization of carbonyl compounds in organic synthesis has traditionally been accomplished via classical enolate chemistry. As α-functionalized carbonyl moieties are ubiquitous in biologically and pharmaceutically valuable molecules, catalytic α-alkylations have been extensively studied, yielding a plethora of practical and efficient methodologies. Moreover, stereoselective carbon–carbon bond formation at the α-position of achiral carbonyl compounds has been achieved by using various transition metal–chiral ligand complexes. This review describes recent advances—in the last 20 years and especially focusing on the last 10 years—in transition metal-catalyzed α-alkylations of carbonyl compounds, such as aldehydes, ketones, imines, esters, and amides and in efficient carbon–carbon bond formations. Active catalytic species and ligand design are discussed, and mechanistic insights are presented. In addition, recently developed photo-redox catalytic systems for α-alkylations are described as a versatile synthetic tool for the synthesis of chiral carbonyl-bearing molecules.

The effect of metalo nt he degreeo ff lexibility upon evacuation of metal-organic frameworks (MOFs) has been revealed with positionalc ontrolo ft he organicf unctionalities. Although Co-, Cu-, and Zn-based DMOFs( DMOF = DABCO MOF,D ABCO = 1,4-diazabicyclo[2.2.2]octane) with ortho-ligands (2,3-NH 2 Cl) have frameworks that are inflexible upon evacuation, MOFs with para-ligands (2,5-NH 2 Cl) showedd ifferent N 2 uptake amountsa fter evacuation by metal exchange. Considering that the structurala nalyses were not fully sufficiently different to explain the drastic changes in N 2 adsorption after evacuation, quantumc hemical simulation was explored. An ew index (h)w as defined to quantify the regularity aroundt he metal based on differences in the oxygen-metal-oxygen angles. Within 2,5-NH 2 Cl, the h value becomes larger as the metal are varied from Co to Zn. Al arge h value meanst hat the structures aroundt he metalc entera re less ordered. These results can be used to explain flexibility changes upon evacuation by altering the metalc ation in this regioisomeric system. Scheme1.Synthesis of regioisomeric DMOFs with different metal salts (colored circle = M 2 secondarybuildingu nit).

A photodegradable nitrophenylene polymer was prepared via ring-opening metathesis polymerization (ROMP). The resulting polymer was degraded in the presence of UVA light without any chemical additives within 1 hour.

Porosity control and structural analysis of metal–organic frameworks (MOFs) can be achieved using regioisomeric ligand mixtures. While ortho-dimethoxy-functionalized MOFs yielded highly porous structures and para-dimethoxy-functionalized MOFs displayed almost nonporous properties in their N2 isotherms after evacuation, regioisomeric ligand-mixed MOFs showed variable N2 uptake amount and surface area depending on the ligand-mixing ratio. The quantity of N2 absorbed was tuned between 20 and 300 cm3/g by adjusting the ligand-mixing ratio. Both experimental analysis and computational modeling were performed to understand the porosity differences between ortho- and para-dimethoxy-functionalized MOFs. Detailed structural analysis using X-ray crystallographic data revealed significant differences in the coordination environments of DMOF-[2,3-(OMe)2] and DMOF-[2,5-(OMe)2] (DMOF = dabco MOF, dabco = 1,4-diazabicyclo[2.2.0]­octane). The coordination bond between Zn2+ and carboxylate in the ortho-functionalized DMOF-[2,3-(OMe)2] was more rigid than that in the para-functionalized DMOF-[2,5-(OMe)2]. Quantum-chemical simulation also showed differences in the coordination environments of Zn secondary building unit surrounded by methoxy-functionalized ligands and pillar ligands. In addition, the binding energy differences between Zn2+ and regioisomeric ligands (ortho- and para-dimethoxy-functionalized benzene-1,4-dicarboxylates) explained the rigidity and porosity changes of the mixed MOFs upon evacuation and perfectly matched with experimental N2 adsorption and X-ray crystallography data.