Intermolecular C-H amination

TABLE 6.3. Silver-Bathophenanthroline Catalysis of a Mild Intermolecular C-H Amination... 

Scheme 6.6. Ligand effects on intermolecular C-H amination catalysis.

Figure 6.4. Pyrazolylborate ligands used for silver-based intermolecular C-H amination.

Fig. 79 Cobalt porphyrin-catalyzed intermolecular C-H amination reactions...

Metal nitrene complexes were used in a number of C-H amination reactions (recent reviews [358, 359]). Copper ketiminate complexes react with azides to nitrene complexes, which were isolated [360]. (p-Ketiminate)copper(I) complex 262 (2.5 mol%) serves therefore as an efficient catalyst for the intermolecular C-H amination of alkylarenes, cycloalkanes, or benzaldehydes 260 using adamantyl azide 261 as the nitrogen source ig. 68) [361]. The corresponding adamantyl amines or amides 263 were isolated in 80-93% yield. Copper complex 262 forms initially a dinuclear bridged complex with 261. From this a copper nitrene complex is generated by elimination of nitrogen, which mediates the hydrogen abstraction from 260. 

Intermolecular C—H amination is a bigger challenge than the intramolecular version (118). Several synthetically useful methods were developed in 2006 and 2007 by different groups (119). Our group tested a new silver system... 

Catalytic intermolecular C H amination has been extensively investigated but the... 

Scheme 12.16 Rh2 (S) nta 4 catalyzed enantioselective intermolecular C H amination (nttl,...

Fig. 10 Efficient intermolecular C-H amination using an electron-deficient Ru porphyrin catalyst...

The invention of selective and efficient protocols for intermolecular C-H amination remains one of the great challenges in methods development. With the... 

Recently, efficient rhodium-catalyzed intermolecular C—H amination reactions have been reported where a sulfonimidamide is used as the nitrene precursor [46]. The functionalizations of various C—H bonds proceed smoothly in this type of intermolecular amidation reaction (Equation 11.20) [47]. When chiral sulfonimida-mides are used, moderate to excellent diastereoselectivities can be achieved. 

Suna developed a one-pot, two-step process for the intermolecular C—H amination of indoles and other electron-rich aromatic systems. Indole 229 is converted to indolyliodonium tosylate 230 (the structure of which was confirmed by X-ray crystallography) the intermediate is stable in MeCN,dichlo-romethane (DCM), and DMSO at room temperature for at least 72 h. Upon exposure to morpholine and catalytic copper salts, aminated indole 231 is isolated in good yield. The scope of competent amines is quite broad alkyl amines, benzylic amines, anilines, and allylic amines are all tolerated.The reaction sequence also works with pyrroles, azaindoles, pyrazoles, and related systems (14JA6920). Gross and colleagues reported the first one-pot synthesis of L-7-iodotryptophan firom 7-iodoindole and serine the biotransformation uses a bacterial cell lysate that can be stored lyophilized for several months and used catalyticaUy (19 examples, 9-81% yield) (140L2622). 

In comparison, intermolecular reaction met high challenges due to both enthalpy and entropy reasons. In 2007, He and coworkers developed a disilver-based new catalyst 11 which showed high efficiency for intramolecular C-H amination reaction (Scheme 10) [32]. Such an intermolecular C-H amination/amidation ran at mild condition. The new catalyst set has successfully been applied to intermolecular amination reaction for the first time (Scheme 11). In the reaction, the catalyst was added in two portions in order to increase the yield. Under typical reaction condition, AgOTf (2 mol%) and ligand (2.4 mol%) were mixed in DCM in a tube for 20 min. Then the substrate (5.0 or 10.0 eqmv.), PhI=NNs (1.0 equiv.) and 4 A molecular sieves (2 g/mmol) were added under N2 atmosphere. The tube was sealed and heated to 50°C for 2 h before another AgOTf (2 mol%) and ligand (2.4 mol%) mixed in DCM were added. The reaction was carried out at 50°C... 

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