Nickel-Catalyzed Regioselective Intermolecular Dialkylation of Alkenylarenes: Generation of Two Vicinal C(sp3)−C(sp3) Bonds Across Alkenes**

We disclose a Ni-catalyzed regioselective dialkylation reaction of alkenylarenes with α-halocarbonyls and alkylzinc reagents. The reaction produces γ-arylated alkanecarbonyl compounds with the generation of two new C(sp³)−C(sp³) bonds at the vicinal carbons of alkenes. This reaction is effective for the use of primary, secondary and tertiary α-halocarboxylic esters, amides and ketones in conjunction with primary and secondary alkylzinc reagents as the sources of two C(sp³) carbons for the dialkylation of terminal and cyclic internal alkenes.     

Walking metals: catalytic difunctionalization of alkenes at nonclassical sites

Migration of metals along a carbon chain is triggered by two of the most common organometallic elementary steps – β-hydride (β-H) elimination and alkene hydrometallation. This process heralds a new future for creating bonds at carbon sites that fall outside the tenets of the conventional wisdom for reactivity and bond formation, and provides an opportunity to leverage β-H elimination to advance the very reaction of alkene difunctionalization it is intrinsically predestined to disrupt. Almost four decades since its genesis, the early adventure for alkene difunctionalization by metal migration was sporadic, and its later development went on a hiatus primarily due to original impetus on arresting β-H elimination for vicinal alkene difunctionalization. With the recent surge on alkene difunctionalization, efforts have been gradually shifting to harnessing the process of β-H elimination to difunctionalize alkenes at sites other than the classical vicinal carbons, termed henceforth nonclassical reaction sites for pedagogical simplicity. In this review article, we extricate and examine the origin and the development of such reactions over the years. This review covers a wide range of reactions for the difunctionalization of alkenes at geminal (1,1), allylic (1,3) and remote (1,n) carbon sites with a variety of coupling partners. These reactions have enabled engineering of complex molecular frameworks with the generation of new carbon–carbon (C–C)/C–C, C–C/C–heteroatom (halogens, O, N, B) and C–B/C–B bonds. The development of these unique transformations is also presented with mechanistic hypotheses and experimental evidences put forward by researchers. Judged by the number of reports emerging recently, it is now strikingly evident that the field of alkene difunctionalization by metal migration has begun to gain momentum, which holds a great future prospect to develop into a synthetic method of enormous potential.

Alkenes can be difunctionalized at unconventional carbon sites by the migration of transition metals through β-hydride elimination and hydrometallation steps.     

Pyrenyl Carbon Nanotubes for Covalent Bilirubin Oxidase Biocathode Design: Should the Nanotubes be Carboxylated?

Understanding the characteristics of nanomaterials in the context of electrode designs for bio‐electrocatalysis is an emerging research direction. Applications for fuel cells, batteries, and biosensors are directly benefited. The objective of this study is to understand the influence of unfunctionalized multiwalled carbon nanotubes (MWNT) in comparison to carboxylated nanotubes (MWNT?COOH) for pi‐pi stacking with 1‐pyrenebutyric acid (Py) and covalent immobilization of bilirubin oxidase (BOD) enzyme toward the resulting oxygen reduction currents. We designed pyrolytic graphite‐edge electrodes modified with MWNT/Py, MWNT?COOH/Py, or only MWNT?COOH for carbodiimide activation and BOD immobilization. The relative increase in surface ?COOH groups as we move from MWNT to MWNT/Py to MWNT?COOH/Py modification is voltammetrically estimated. Although the MWNT?COOH/Py displayed the highest relative amount of surface ?COOH groups, the oxygen reduction current was the largest for the BOD‐immobilized MWNT/Py electrode than others. Results indicate that unfunctionalized MWNT is the optimal choice for pi‐pi stacking with pyrene linkers and covalent BOD immobilization as biocathode for energy devices. Favorable hydrophobic MWNT surface to interact more closely with the electron‐receiving T1 Cu site of BOD, as opposed to the relatively polar and more defective MWNT?COOH material due to functionalization, is suggested to be one of the underlying factors for the observed electrocatalytic trend.