Photocatalysis for Heterocycle Formation and Functionalisation

Heterocyclic compounds are an important class of organic chemicals that feature one or more heteroatoms in their ring systems. Such compound class have played an important role in our daily lives, as they are ubiquitous in natural products, pharmaceuticals, and other biologically active molecules. Many heterocyclic scaffolds have been identified as privileged structural units in pharmacologically active compounds. According to statistics, more than 90% of novel pharmaceuticals contain at least one heterocycle. Advances in modern synthetic techniques, such as organocatalytic cycloadditions, metal-catalyzed cross-coupling reactions, have offered many efficient and rapid approaches for assembly of diverse heterocycles of various ring sizes. However, given increasing need for expansion of the available drug-like chemical space and from both environmental and economical viewpoints, it is still highly desirable to develop new efficient and practical methodologies toward heterocycle synthesis and functionalization under "green and sustainable" conditions. Photocatalysis is emerging as a powerful tool to access diverse high-energy intermediates in a controlled and selective fashion, and capable of promoting numerous challenging bond formation and novel chemical transformation. This re-merging catalytic strategy fits with green chemistry principles and has significantly spurred many innovative approaches that use of low energy photons as a controllable energy source to enable heterocycle formation and functionalization under mild conditions. In this book, we have tried to cover some interesting aspects of the development of photocatalytic reactions that are aimed to construct diverse heterocyclic compounds. Specifically, this major content is devoted to the following research topics, including N-heterocycle formation (Chapters 1, 4, and 6), functionalization of N-heterocycles (Chapters 2, 3, and 8), chiral heterocycle formation (Chapter 5), dearomatization of heterocycles (Chapter 7), fused thiophene formation and functionalization (Chapter 9), construction of axially chiral heterocyclies (Chapter 10), and photoinduced biocatalytic heterocycle formation (Chapter 11). It is our hope that this book, in addition to being of interest to practitioners of medicinal chemistry and organic synthesis who need an introduction to this area, will also be found inspiriting and stimulating by undergraduate and graduate students.