Radical-type Reactions Controlled by Cobalt: From Carbene Radical Reactivity to the Catalytic Intermediacy of Reactive o-Quinodimethanes

In this account, we summarize our recent efforts in the fields of ‘open-shell organometallic chemistry’ and ‘metalloradical catalysis’. We focus in particular on the use of so-called ‘carbene radicals’ for the synthesis of a variety of useful synthons for organic chemistry. We further show that unexpected reactivity arises from catalytic synthesis of unusual o-quinone methide and o-quinodimethane intermediates that undergo subsequent rearrangements to uncommon products.

1 Introduction

2 General (Fischer-Type) Carbene and Nitrene Reactivity and Their Relation to Carbene and Nitrene Radical Reactivity

3 Carbene and Nitrene (Radical) Precursors

4 Formation and Intrinsic Radical-Type Reactivity of Carbene and Nitrene Radicals

5 Types of Cobalt Catalysts Used in Reactions Involving Carbene and Nitrene Radicals

6 Applications of Cobalt-Catalyzed Ring-Closure Reactions via ­Carbene Radicals

7 Intermediacy of o-Quinone Methide and o-Quidodimethanes in Carbene Ring-Closing Reactions

8 Conclusion