Synthesis of 5-, 6- and 7-azaindoles via palladium-catalyzed heteroannulation of internal alkynes

Palladium-catalyzed reaction of 2-iodoferrocenyl alcohols with internal alkynes: Synthesis of functionally 1,2-disubstituted ferrocenes and ferroceno-pyrans

“…The reaction between diphenylacetylene (6a) and ferrocenyl alcohol 1 was chosen as the model to explore the "optimal" reaction conditions. Initially, we tested the conditions applied previously for the palladium-catalyzed annulation of internal alkynes by various aryl halides bearing a nucleophilic group in their ortho positions [87,88,91,92]. It was reported that these annulation reactions proceed in a regioselective manner and afford the heterocycles in high yields under the catalytic conditions containing, in general, Pd(OAc) 2 or Pd(dba) 2 , solid ionic bases and chloride sources such as LiCl and n-Bu 4 NCl.…”

“…It was reported that these annulation reactions proceed in a regioselective manner and afford the heterocycles in high yields under the catalytic conditions containing, in general, Pd(OAc) 2 or Pd(dba) 2 , solid ionic bases and chloride sources such as LiCl and n-Bu 4 NCl. The most of the described annulation reactions were carried out in DMF at temperatures of 80e120 C [87,88,91,92]. The literature protocols also imply that the presence of a phosphine ligand in the catalytic cocktail was not always essential for success [87,88,91,92].…”

“…The most of the described annulation reactions were carried out in DMF at temperatures of 80e120 C [87,88,91,92]. The literature protocols also imply that the presence of a phosphine ligand in the catalytic cocktail was not always essential for success [87,88,91,92]. We have employed analogous conditions in our model reaction.…”

A General and Efficient Synthesis of Azaindoles and Diazaindoles

“…2 The 4-, 5-, 6-and 7-azaindole isomers have been generated either by the cyclization of ortho-nitro-alkenylpyridines 3 or the palladium-catalyzed heteroannulation of internal alkynes with ortho-aminoiodopyridines. 4 Recently, the addition of the dianion of 3-amino-4-picoline to carboxylic esters has been reported for the synthesis of 6-azaindoles. 5 However, the most general method used for the synthesis of azaindoles is the cyclization of ortho-amino-alkynyl pyridines.…”

“…Alternatively, strong bases have been employed: cyclizations to give 4-or 5-azaindoles have been performed with NaOEt in EtOH; 12 4-azaindoles have been generated using NaNH 2 in DMF, 13 and 4,7-diazaindoles have been cyclized using methylamine. 14 More recently, t-BuOK or KH in NMP has been used to synthesize various azaindoles and diazaindoles.…”