Synthesis of five- and six-membered nitrogen-containing heterocyclic compounds from carboxylic acids iminoesters

Product Class 4: Benzimidazoles

“…The use of polyphosphoric acid or hydrochloric acid as the catalytic condensing agent with 1,2-diaminoarenes and carboxylic acids means that the diamine often competes successfully with the carbonyl oxygen atom for the acid proton. [7,8,116,118] This general approach has been adapted to solid-phase synthesis by generating an 1,2-nitroaniline species on a solid support, reducing it to the 1,2-diaminoarene, and cyclizing it in situ with an arenecarboximidate to give high yields (54±93%) of the pure products. Such reagents are imino ethers or imidates, which can be pre-prepared from the nitriles [114] or made in situ.…”

“…For the corresponding anion the shifts are ä 150.5 (C2), 116.4 [C4 (7)], 120.1 [C5 (6)], and 143.9 (bridgehead carbons); the carbon electron densities are all higher. For the corresponding anion the shifts are ä 150.5 (C2), 116.4 [C4 (7)], 120.1 [C5 (6)], and 143.9 (bridgehead carbons); the carbon electron densities are all higher.…”

Cyanamides in cyclization reactions with anthranilates, 2-aminophenyl ketones, and methyl 2-(3-oxopiperazin-2-yl)acetate

“…Imino esters, 3 cyanates, isocyanates, amides, or thioamides 4 are usually used for this purpose. It turned out that they can be successfully replaced by cyanamides.…”

Synthesis of 2,5-disubstituted 1,3,4-oxadiazoles containing a sterically hindered 4-hydroxy-3,5-di(tert-butyl)phenyl group

“…Ia-e Ha-f It is well known [8,9] that convenient compounds used in the synthesis of 1,3,4-oxadiazoles are hydrochlorides of iminoesters of carboxylic acids. In the present study, the starting compounds used were hydrochlorides of ethyl iminoesters of 4-hydroxy-3,5-di(tert-butyl)benzoic (Ia), fl-HDBP-propionic (Ib), s-HDBP-thiocyanic (It), HDBP-thioacetic (Id), and fl-HDBP-propionic (Ie) acids.…”