In this contribution, we provide a comprehensive overview of C−H activation methods promoted by NHC−transition metal complexes, covering the literature since 2002 (the year of the first report on metal−NHC-catalyzed C−H activation) through June 2019, focusing on both NHC ligands and C−H activation methods. This review covers C−H activation reactions catalyzed by group 8 to 11 NHC−metal complexes. Through discussing the role of NHC ligands in promoting challenging C−H activation methods, the reader is provided with an overview of this important area and its crucial role in forging carbon−carbon and carbon−heteroatom bonds by directly engaging ubiquitous C−H bonds.

An extremely simple and rapid (seconds) approach is reported to directly synthesize gram quantities of P-doped graphitic porous carbon materials with controlled P bond configuration. For the first time, it is demonstrated that the P-doped carbon materials can be used as a selective metal free catalyst for aerobic oxidation reactions. The work function of P-doped carbon materials, its connectivity to the P bond configuration, and the correlation with its catalytic efficiency are studied and established. In direct contrast to N-doped graphene, the P-doped carbon materials with higher work function show high activity in catalytic aerobic oxidation. The selectivity trend for the electron donating and withdrawing properties of the functional groups attached to the aromatic ring of benzyl alcohols is also different from other metal free carbon based catalysts. A unique catalytic mechanism is demonstrated, which differs from both GO and N-doped graphene obtained by high temperature nitrification. The unique and unexpected catalytic pathway endows the P-doped materials with not only good catalytic efficiency but also recyclability. This, combined with a rapid, energy saving approach that permits fabrication on a large scale, suggests that the P-doped porous materials are promising materials for "green catalysis" due to their higher theoretical surface area, sustainability, environmental friendliness, and low cost.

Scheme 10. Spirocyclization of α,β-Unsaturated Lactones toward the Synthesis of Stolonidiol by Procter Scheme 11. Synthesis of cis-Hydrindanes via 5-exo-Trig Cyclization by Procter Chemical Reviews Review dx.

CONTENTS 1. Introduction 5702 2. General Properties of Bridged Lactams 5703 2.1. Distortion Parameters of Bridged Lactams 5703 2.2. Bond Lengths of Bridged Lactams 5703 2.3. Spectroscopic Properties of Bridged Lactams 5703 2.4. Analogy of Bridged Lactams to Bridgehead Olefins 5704 2.5. Chemical and Biological Significance of Distorted Amides 5704 3. Synthesis of Historically Important Bridged Lactams 5704 3.1. Quinuclidone Derivatives 5704 3.2. Adamantanone Derivatives 5707 4. Synthesis of Bridged Lactams with the N−(CO) Bond on a Two-Carbon or Larger Bridge, ([m. (≥2).n] Type) 5708 4.1. Condensation Reactions Forming the N− C(O) Bond 5708 4.2. Heck Reactions 5711 4.3. Diels−Alder Reactions 5712 4.4. Carbene Insertion Reactions 5713 4.5. Reactions via Radical Intermediates 5714 4.6. Miscellaneous Examples 5714 5. Synthesis of Bridged Lactams with the N−(CO) Bond on a One-Carbon Bridge, ([m.1.n] Type) 5715 5.1. Carbene Insertion Reactions 5715 5.2. Schmidt Reactions 5716 5.3.

The concept of using amide bond distortion to modulate amidic resonance has been known for more than 75 years. Two classic twisted amides (bridged lactams) ingeniously designed and synthesized by Kirby and Stoltz to feature fully perpendicular amide bonds, and as a consequence emanate amino-ketone-like reactivity, are now routinely recognized in all organic chemistry textbooks. However, only recently the use of amide bond twist (distortion) has advanced to the general organic chemistry mainstream enabling a host of highly attractive N-C amide bond cross-coupling reactions of broad synthetic relevance. In this Minireview, we discuss recent progress in this area and present a detailed overview of the prominent role of amide bond destabilization as a driving force in the development of transition-metal-catalyzed cross-coupling reactions by N-C bond activation.