Photoinduced Biomimetic Room-Temperature C-O Bond Cleavage over Mn Doped CdS

Selective C-O bond cleavage is an efficient way for the biomass valorization to value-added chemicals, but is challenged to be operated at room temperature via conventional thermal catalysis. Herein, inspired from the DNA biosynthesis which involves a radical-mediated spin-center shift (SCS) C-O bond cleavage process, we report a biomimetic room-temperature C-O bond cleavage of vicinal diol (HOCHCH-OH). We construct a Mn doped CdS (Mn/CdS) as a photocatalyst to mimic the biologic SCS process. The Mn site plays pivotal role: (1) accelerates the photo-induced carrier separation, promoting the hole-mediated C-H bond cleavage to generate carbon-centered radicals, and (2) serves as the binding site for -OH groups, making it to be an easier leaving group. Mn/CdS achieves 0.28 mmol gcat -1  h-1 of hydroxyacetone (HA) from glycerol dehydration at room temperature under visible light irradiation, which is 3.5-fold that over pristine CdS and 40-fold that over bulk MnS/CdS. This study provides a new biomimetic room-temperature C-O bond cleavage process, which is promising for the biomass valorization.

1,2-Radical Shifts in Photoinduced Synthetic Organic Transformations: A Guide to the Reactivity of Useful Radical Synthons

The exploration of 1,2-radical shift (RS) mechanisms in photoinduced organic reactions has provided efficient routes for the generation of important radical synthons in many chemical transformations. In this Review, the basic concepts involved in the traditional 1,2-spin-center shift (SCS) mechanisms in recently reported studies are discussed. In addition, other useful 1,2-RSs are addressed, such as those proceeding through 1,2-group migrations in carbohydrate chemistry, via 1,2-boron shifts, and by the generation of α-amino radicals. The discussion begins with a general overview of the basic aspects of 1,2-RS mechanisms, followed by a demonstration of their applicability in photoinduced transformations. The sections that follow are organized according to the mechanisms operating in combination with the 1,2-radical migration event. This contribution is not a comprehensive review but rather aims to provide an understanding of the topic, focused on the more recent advances in the field, and establishes a definition for the nomenclature that has been used to describe such mechanisms.

Application of the Spin-Center Shift in Organic Synthesis

Spin-center shift (SCS) is a radical process involving 1,2-radical translocation along with a two-electron ionic movement, such as elimination of an adjacent leaving group. Such a process was initially observed in some important biochemical transformations, and the unique property has also attracted considerable interest in synthetic chemistry. Experimental, kinetic, as well as computational studies have been performed, and a series of useful radical transformations have been developed and applied in organic synthesis based on SCS processes in the last 20 years. This Perspective is an overview of radical transformations involving the SCS mechanism.