Science of Synthesis

Liu, J.; Johnson, J. A., Science of Synthesis: N-Heterocyclic Carbenes in Catalytic Organic Synthesis, (2016) 2, 99.

General Introduction

Alkene metathesis polymerizations represent perhaps the most versatile class of polymerization reactions for the synthesis of functional macromolecular architectures. Over the past few decades, N-heterocyclic carbenes (NHCs) have played a critical role in the development of alkene metathesis polymerization; they appear as ancillary ligands in a number of the most widely used polymerization catalysts and initiators. Furthermore, novel N-heterocyclic carbenes have expanded the application of alkene metathesis to new areas, including polymerization in aqueous systems, the synthesis of stereoregular polymers, and the growth of NHC-anchored polymers from gold substrates. Alkene metathesis based polymerization reactions that depend on metal complexes with N-heterocyclic carbene ligands will be discussed in this chapter. The first section introduces ring-opening metathesis polymerization (ROMP; Section ‌2.1.5.1‌), followed by additional sections on applications of ROMP, including block polymers (Section ‌2.1.5.1.2‌), molecular bottlebrush polymers (Section ‌2.1.5.1.3‌), and ROMP using initiators with modified N-heterocyclic carbene ligands (Section ‌2.1.5.1.4‌). These sections are followed by a discussion of acyclic diene metathesis polymerization (ADMET; Section ‌2.1.5.2.1‌) and cyclopolymerization (Section ‌2.1.5.2.2‌). Finally, the chapter concludes with a brief discussion of alkene metathesis polymerization with non-ruthenium-based N-heterocyclic carbene–metal complexes (Section ‌2.1.5.3‌).