Arylations C=N bonds

The switching on of luminescence upon Ca2+ binding to 1 has a special cause in addition to the general arguments advanced earlier in this essay. Ca2+ demands an optimal spatial draping of ligating atoms around it in spite of its s-block character. This arrangement is best attained by rotation about the aryl C-N bonds in the N-aryl iminodiacetate moie-... 

The barriers to rotation about the aryl C—N bonds were determined by DNMR in 3-aryl-2-benzyl-4(3/f)-quinazolinones 135 (72TL5239 75CJC3431) and in imide 135a (76AJC295) (Scheme 99). 

Tetrahydrocarbazoles and related fused systems have been accessed by a route relying on palladium-catalyzed tandem formation of alkenyl and aryl C-N bonds. For instance, the starting triflate 477 could be efficiently transformed into the target system 478 by amination with aniline (Equation 133) <2005AGE403>. Annulation of (2-triflyloxy)phenethyl carbonates with amides in the presence of a palladium catalyst has been used as a route to various N-substituted indoline derivatives <2005OL4777>. 

The first palladium-catalyzed formation of aryl C-N bonds was reported in 1983 by Migita and co-workers, Eq. (1) [14], The reaction of electronically neutral aryl bromides and aminotin compounds in the presence of catalytic [(o-tol)3P]2PdCl2 resulted in the efficient preparation of the corresponding aniline in moderate to good yield. This seminal discovery was limited by the necessity to use the thermally and moisture sensitive tributyltin amides, however. 

The Buchwald-Hartwig Pd-catalyzed aryl C—N bond formation... 

The same nucleophilic substitution chemistry can be manipulated by means of microwave irradiation to afford a variety of cyclic amines as building blocks in natural product syntheses via double V -alkylation of primary amines (Scheme 11). The protocol circumvents the difficulty associated with running multi-step reactions to assemble Y -aryl azacycloalkanes and avoids the use of expensive metal catalysts in building aryl C-N bonds. Further, reactive functional groups, such as carbonyl, ester, and hydroxyl, remain unaffected under these mild reaction conditions. The V-alkylation reaction is now extended to hydrazines as well. ... 

Ru-catalyzed Suzuki-type cross-coupling reactions of aniline derivatives and organoboronates have been achieved via unreactive aryl C—N bond cleavage (Equation 11.48) [109]. The proposed reaction pathway is a sequence of oxidative addition of an unreactive aryl C—N bond to the late transition metal complex, followed by transmetalation between the Ru-NR2 species and organoboronates, and reductive elimination. 

Synthetic studies on natural products with aromatic nitrogen heterocycles based on the development of methods for the formation of aryl C-N bond 13YZ1065. 

The potential importance of rotational dynamics about the aryl C-N bond in asymmetric Mizoroki-Heck cyclizations of o-iodoacrylanilides was highhghted in a recent study by Curran and coworkers [68]. Because of the presence of two ortho substituents, racemic ( )-acryl o-iodoanilide 117 could be resolved by preparative high-performance liquid chromatography, and the enantiomers were shown to have a barrier for interconversion of 26 kcalmol" (Scheme 16.30). Although these conformational stereoisomers would racemize readily at the elevated temperatures typically used in asymmetric Mizoroki-Heck... 

One of the most versatile and widely employed methods for the construction of aryl C—N bonds is the palladium-catalyzed cross coupling of amines with aryl halides and related electrophiles [4]. These reactions are believed to occur as shown in Scheme 1.1, with the coupling initiated by oxidative addition of the aryl halide to a Pd° complex. The resulting intermediate 1 is converted to a palladium(aryl)(amido) complex 2 through reaction with the amine substrate in the presence of base. Finally,... 

The first account of palladium-catalyzed aryl C—N bond formation came from Migita in 1983 [6]. Their report described the coupling of aminostannanes with aryl halides and went on to become the foundation of modem C—N bond-forming methodology. However, it wasn t until the research groups of Buchwald [7] and Hartwig [8], independently, reported tin-free catalytic amination reactions that the synthetic potential of these processes became apparent. 

Under ruthenium-catalyzed ortho-C-H activation and intramolecular C-N bond formation, the condensation of iminophosphoranes (in situ generated from acyl azides and triphenylphosphine) with internal alkynes afforded a variety of isoquinolinone derivatives (Eq. (7.43)) [53]. The regioselective insertion of unsymmetrical alkynes led to an (aryl)C-N bond formation. Thiophene and indole-based acyl azides were also compatible for this transformation. A domino reaction sequence via coordination of ruthenium with Af-atom of iminophosphoranes, ort/zo-cyclometalation, alkyne insertion, protonation, and reductive elimination was proposed for the catalytic cycle. Based on and NMR experiments, the involvement of benzamide during the reaction process was ruled out. 

The first example of the formation of an aryl C-N bond via a Pd-catalyzed cross-coupling reaction of an aryl hahde was reported in 1983 by Migita and coworkers [22,23]. During the course of their studies on the reactivity of organotin compotmds,... 

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