Subject Buchwald-Hartwig

The second coupling component, 6-aminocarbazole 1082, was prepared starting from the same known O-tosylate 1063 (165,665). Thus, Buchwald-Hartwig palladium-catalyzed amination of 4-bromonitrobenzene (1076) with 1063 afforded the diaryla-mine 1077. Treatment of 1077 with an excess of Pd(OAc)2 in acetic acid led to the carbazole 1078 in 53% yield. After protection of the carbazole nitrogen with a 2-trimethylsilylethoxymethyl (SEM) group, the product 1079 was subjected to alkaline... 

Many other industrial applications at large scale are known. This subject has been comprehensively reviewed by Busacca et al. [37], and we will highlight one example here, the case of torcertrapib - which is a powerful cholesteryl ester transfer protein (CETP) inhibitor invented by Pfizer [38]. The key step in this synthesis - which can be scaled-up to multi-kilograms - is a Buchwald-Hartwig reaction involving very cheap l-chloro-4-trifluoromethylbenzene and a chiral amine in the presence of PdfOAcj and DavePhos (Scheme 2.8). Interestingly, PhB(OH)2 was added in order to activate the catalyst. 

In a similar fashion, the resin-bound 5-bromo-2-aminobenzothiazole was subjected to a microwave-assisted Buchwald-Hartwig amination " with morpholine using BuONa as the base and a catalytic system comprising Pd(PPh3)4 and X-Phos in DMF at 160°C for 1 h. The product was cleaved from the resin using the previous conditions (Scheme 8.24). 

One of the syntheses of 198 is based on pyrazine 200 (Scheme 47) [165, 166]. Compound 200 was transformed to methoxy derivative 201 via diazotization step 201 was then subjected to Buchwald - Hartwig amination to give 202. Ester 202 was transformed to amide 203 diazotization of 203 in the presence of pyridine hydrofluoride led to the formation of fluoro derivative 204. The last step of the synthesis included deprotection of the methyl ether to give 198. 

The first application of the single-step procedure to the synthesis of azacafix-arenes was laimched by Ito et al., who prepared a series of azacafix[ ]arenes 4a-f with different ring sizes (w = 3 to 8) [16,17]. As shown in Scheme 2, starting from the N-methylation of 3-bromoaniline (2) in 3 steps, the resultant 3-bromo-N-methylaniline (3) was subjected to the Buchwald-Hartwig aryl amination reaction to yield azacaUxarenes 4a-f, which were isolated by medium-pressure liquid chromatography. 

Although this reaction is relatively new, it has already been the subject of several reviews Wolfe, J. P. Wagaw, S. Marcoux, J.-F Buchwald, S. L. Acc. Chem. Res. 1998, 31, 805-818 Hartwig, J. F. Acc. Chem. Res. 1998, 31, 852-860 and Hartwig, J. F. Angew. Chem. Int. Ed. 1998, 37, 2046-2067. Innumerable conditions have been developed however, probably the easiest conditions to try for a first pass reaction are shown below. 

K2CO3 in tBuOH is also a suitable base for substrates bearing ester moieties [54a]. When using liHMDS as base, electrophiles with acidic moieties, such as alcohols, carboxylic acids, and amides, can readily be subjected to the Hartwig-Buchwald aminations with primary amines (Scheme 13.38). 

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