Group 6 Dihapto-Coordinate Dearomatization Agents for Organic Synthesis.

This review covers publications ranging from 2005 to 2017 concerning the organic reactions of aromatic ligands η2 -coordinated to tungsten or molybdenum and the use of these reactions in the synthesis of novel organic substances. An emphasis is placed on C-C bond-forming reactions using conventional building blocks of organic synthesis such as acetals, enolates, Michael acceptors, acylating reagents, and activated aromatics. Substrates activated by the metal include arenes, pyridines, pyrroles, pyrimidines, furans, and thiophenes. General reactivity patterns are elucidated, as well as stereochemical preferences. These trends are compared to those of osmium and rhenium forebears as well as to the reactivity patterns of other methods of stoichiometric transition-metal-based dearomatization (i.e., η6 -arene complexes).