Catalyst-free Reductive Hydrogenation Or Deuteration Of Carbon-heteroatom Bonds Induced By Light

Hydrogenolysis of C-heteroatom bonds in aromatics such as arylamines,arenols,and haloarenes finds increasingly important roles in the regioselective defunctionalization of aryl derivatives.These reactions provide key intermediates or pivotal deuterium-labeled arenes in the production of pharmaceuticals,pigments,and agrochemicals from readily accessible chemicals or renewable biomass.In particular,deuterium incorporation techniques have found widespread applications in broad areas such as mechanistic studies of organic reactions and new drug discovery and developments.Significant advances have been made in the reductive removal of amine groups,phenol groups,and halogens.The need for expensive metals/catalysts/ligands,strong basic or acidic reagents,or unstable/explosive intermediates limits the applications of some of those protocols.So,we describe here a simple and catalyst-free photochemical strategy for the direct reduction of carbon-heteroatom bonds,and the results are divided into following two parts:Chapter 1 Catalyst-free reductive hydrogenation or deuteration of aryl-heteroatom bonds induced by lightThis chapter describes a simple,transitionmetal-free strategy of photoinduced hydrogenation or deuteration of quaternary arylammonium salts,aryl triflates,and aryl halides.The reduction produces Ar-H and Ar-D in good to excellent yields and deuteration ratios under mild conditions without the use of external reductants.The transformation is distinguished by a broad scope that includes electron-rich and electron-poor aryl or heteroaryl substrates,and the photoinduced deuteration of quaternary arylammonium salts and aryl triflates under catalyst-free conditions was achieved which was rarely explored.Radical clock experiments indicate the formation of aryl radical intermediates that can also be trapped by phenols.This redox-neutral strategy can hopefully extend to other systems and provides green approaches for deuterium incorporation.Chapter 2 Catalyst-free reductive hydrogenation of alkyl-heteroatom bonds induced by lightUsing benzyltrimethylammonium salt as raw material,the light induced reduction hydrogenation of carbon nitrogen bonds of aliphatic amines was investigated.The solvents and bases were screened respectively,and the optimal reaction conditions were determined,which provided a basis for further reduction hydrogenation of other aliphatic carbon heterobonds.