C-N bond-forming step

In contrast, few examples of reductive elimination reactions that form the C-N bond in amines are known. Only in the past several years have complexes been isolated that undergo these reactions [49-54]. These reductive eliminations are the crucial C-N bond-forming step of the aryl halide and triflate amination chemistry discussed in this review. Information on how these reactions occur, and what types of complexes favor this process, has been crucial to the understanding and development of new amination catalysts [50],... 

Indoles have proved a popular target for synthetic methodologies utilizing key palladium- and copper-catalyzed C—N bond formations. A plethora of routes have been developed for construction of the pyrrole ring incorporated in an indole system [11-15]. The main disconnections [D-1 to D-7] which feature a catalysed C—N bond-forming step, are illustrated in Scheme 24.1. 

Synthesis This is part of Kutney s quebrachamine synthesis (j. Amer, Chem. Soc., 1966, 8S, 3656). He found that if X = OEt, both C-N bond-forming operations could be carried out in one step. The synthesis is actually much easier to carry out than expected ... 

Finally, a Nicholas-type reaction is presumably responsible for an unexpected result reported by Alcaide. During their work devoted to the application of the PKR in the field of -lactams and azetidines they reacted complexed azetidine 91 with TMANO, isolating a mixture of the expected PK product 92 and by-product 93. The formation of 93 is believed to be a consequence of the ionization of the propargylic C - N bond at the cobalt-acycle step. The crowded metallacycle formed after the insertion of the olefin (93), would prompt the cleavage of the C - N bond, forming an ionic species (94) that would trap a hydride, possibly from a cobalt hydride giving 95, which then would follow the usual pathway towards the cyclopen-tenone (Scheme 27) [124],... 

Kamikawa used two different Pd-catalyzed C-N bond-forming reactions for the convergent preparation of several phenazines [93]. After intermolecular coupling was achieved, the nitro group was reduced. Subsequent Pd-catalyzed cyclization afforded the desired product in 80% yield over three steps, Eq. (175). 

Data for the CNH reaction of indole over the same catalysts are displayed in Fig. S (CNH refers to the first C-N bond-breaking step forming o-ethyl aniline, e.g. the disappearance of... 

An alternative to the 2-halo-carbonyl component is an epoxide or N-tosylaziridine. A cascade sequence was used to bring about formation of the three-membered ring and also reaction with a suitable thioamide in one pot. Whether it is the S-alkylation or the C-3-C-4 bond forming step that occurs first is not known. By producing optically active epoxides/Af-tosylaziridines in situ, the final thiophenes were also optically active (Scheme 69 [112] shows an aziridine sequence). 

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