N-C Aryl Bonds

The proposed mechanism involves the initial formation of the palladacycle 118 via the Catellani reaction sequence between the aryl iodide and norbornene (Scheme 3.32). Coordination of the aziridine 125 followed by oxidative addition of the N-C single bond by Pd leads to the intermediate 129. The fission of N-C single bond is commonly observed in transition-metal-catalyzed reactions with aziridines. Chemoselective C-C bond formation gives 130, which on decarbopalladation affords palladacycle 131 and extrudes norbornene. Reductive elimination furnishes... 

Scheme 15.20 C-N/C-O bond-forming reactions of aryl boronic acids with amines, amides or phenols.

The barriers for rotation about the C(carbene)-C(aryl) bond in [Fe(C5H5)(CO)2(CHC6H4R-4)] are 38 (R = H) and 44 (R = Me) kJ moP and were determined from coalescence of the two ortho-hydrog n signals. The arene ring is in the plane of the Fe-CH-C(aryl) atoms bisecting the CO ligands... 

M.M. Guru, M.A. Ali, T. Punniyamurthy, Copper-mediated synthesis of substituted 2-aryl-N-benzylbenzimidazolesand2-arylbenzoxazoles via C-H functionalization/C-N/C-O bond formation, J. Org. Chem. 76 (2011) 5295-5308. 

The first example of Rh-catalyzed C-H coupling of 2-phenylpyridines with 7-azabenzonorbornadienes to provide czs-fused dihydrocarbazoles 39 was reported by Li and coworkers (Eq. (5.38)) [23]. The C-N bond forms via a double C-H activation, in which a seven-membered rhodacyclic complex is a key intermediate as a result of stereoselective insertion of the olefin into the Rh-C(aryl) bond. This strategy has also been employed for the synthesis of dihydrocarbazoles by using various directing groups. 

Abstract Although requiring the use of stoichiometric amounts of metal and harsh conditions, the copper-mediated coupling reactions of aryl halides with amines and phenols (Ullmann craidensatiOTis), amides and carbamates (Ullmann-Goldberg condensations), or activated methylene compounds (Ullmann-Hurtley condensations) have been for a long time useful methods for the formation of C(aryl)-N, C(aryl)-0, and C(aryl)-C bonds. In 2001, a renaissance of the Ullmann reaction has been initiated with the discovery of versatile new copper catalytic systems for C-C, C-N, or C-O coupling under mild temperature ccmditions. 

Unsubstituted 3-alkyl- or 3-aryl-isoxazoles undergo ring cleavage reactions under more vigorous conditions. In these substrates the deprotonation of the H-5 proton is concurrent with fission of the N—O and C(3)—-C(4) bonds, giving a nitrile and an ethynolate anion. The latter is usually hydrolyzed on work-up to a carboxylic acid, but can be trapped at low temperature. As shown by Scheme 33, such reactions could provide useful syntheses of ketenes and /3-lactones (79LA219). 

The first benzazetidine (243) was isolated from the photolysis of 3-phenyldihydroben-zotriazine (242) (66JA1580). Another route to benzazetidines involving formation of the N to aryl-C bond utilizes intramolecular nucleophilic substitution via aryne (287). It is not general, however, and is only satisfactory when R and/or are alkoxy groups. The reaction also fails for iV-alkylamines (78LA608). 

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