Natural deep eutectic solvents in the hetero-Diels–Alder approach to bis(indolyl)methanes

Diels–Alder Cycloaddition Reactions in Sustainable Media

“…Pinho e Melo and coworkers disclosed the first example of an inverse electron demand hetero-Diels-Alder reaction in natural DESs [73]. Oxime-and hydrazone-bis(indolyl) methanes (BIMs) 71 were obtained as single Z-isomers via one-pot bis-hetero-Diels-Alder reaction of nitrosoalkenes and azoalkenes with indoles using a ternary mixture of water with ChCl/Gly (Scheme 16).…”

Enzymatic approach to cascade synthesis of bis(indolyl)methanes in pure water

“…Enzymatic synthesis of bis(indolyl)methanes was carried out using lipase TLIM as catalyst. Based on literatures, 18,20 it can be explained by a proposed mechanism depicted in Scheme 3. We supposed that the catalytic active site of lipase TLIM plays a vital role in the cascade reaction.…”

“…7 Bis(indolyl)methanes are generally obtained from cascade reactions of indole with carbonyl compounds catalyzed by protic or Lewis acids, which may be easily captured by nitrogenous compounds so as to bring some problems for the synthesis of bis(indolyl)methanes. 8 Recently, various novel catalysts have been reported to synthesize bis(indolyl)methanes, such as aza-crown ether ionic liquids supported on magnetic Fe 3 O 4 @SiO 2 core-shell particles, 9 nanocomposites ZrO 2 -Al 2 O 3 -Fe 3 O 4 , 10 1-hexenesulphonic acid sodium salt under ultrasound irradiation, 11 SDS, 12 zeolite, 13 graphene oxide, 14 AgOTf, 15 LASSC catalytic system, 16 meglumine catalyst, 17 NADES, 18 etc. However, there are some shortcomings in the most of catalytic methods mentioned above including expensive or complicated catalyst used, relative high temperature and excessive substrate needed, volatile organic solvent employed, etc.…”

Ethyl 7-Acetyl-8a-methyl-3-(1-phenyl-1H-tetrazol-5-yl)-1,4,4a,5,6,8a-hexahydro-7H-pyrano[2,3-c]pyridazine-1-carboxylate

“…Nitroso-and azoalkenes, including 3-tetrazolyl-and 3-triazolyl derivatives, were used for the alkylation of five-membered heterocycles, namely pyrroles, dipyrromethanes, indoles and furans [2][3][4][5][6][7][8][9][10][11]. Furthermore, new routes to bis(heteroaromatic)methanes have been developed via two consecutive hetero-Diels-Alder reactions (or conjugated additions) of the in situ generated nitrosoalkenes and azoalkenes, namely the synthesis of dipyrromethanes [12,13], bis(indolyl)methanes [14][15][16], bis(pyrazol-1-yl)methanes [17] and tetrapyrrolic compounds [18]. The latter led to the development of a novel synthetic approach to meso-substituted corroles, comprising the synthesis of bilanes via the reaction of nitrosoalkenes with dipyrromethanes, followed by oxidative macrocyclization [18].…”