Reaction of 2‐aminobenzimidazole with bifunetional carboxylie acid derivatives. Formation of pyrimido[1,2‐a] benzimidazolones

Abstract

2‐Aminobenzimidazole reacts with α,β‐unsaturated carboxylic acid chlorides or esters to give only pyrimido [1,2‐a] benzimidazol‐2‐(1H) ones. β‐Ethoxymethylenemalonie acid derivatives or β‐ketocarboxylic acid derivatives give only pyrimido [1,2‐a] benzimidazol‐4‐(1H)ones. Structural assignments based on nmr and chemical manipulations are discussed.

Reaction of 2-aminobenzazoles with dimethyl 2-aminofumarate. Synthesis and nuclear magnetic resonance spectroscopy of 4-oxopyrimido[2,1-b]benzazoles

“…Found: C, 59.6; H, 2.9; N, 13.8. From DMAF-Derived Ester 2a. A mixture of 2a (1.30 g, 5.00 .mmol) and NaOH (0.30 g, 7.5 mmol) in 70 mL of water was heated at 70 °C overnight, by which time all solids had dissolved. The solution was cooled and acidified with concentrated HC1 to precipitate a solid which was collected by filtration, washed with water, and dried to give 0.69 g (56%) of 4-oxopyrimido[2,l-b]benzothiazole-2-carboxylic acid: mp 261-263 °C dec; IR 5.74 (sh), 5.87 pm.…”

Synthesis, Reactions, and Pharmacological Applications of 2-Aminobenzimidazoles: An Update

“…40) and ( 45) were obtained, respectively. Within the latter case, the nitrile (41) was also obtained [70] (Scheme 39).…”

Synthesis of pyrimido[1,2-a]benzimidazoles from ethyl 2-ethoxymethylidene-3-oxo-3-(polyfluoroalkyl)propionates

“…Such substrates could give rise to alternative reaction pathways with formation of various pyrimido [1,2-a]benzimidazoles. However, the condensations of benzimidazol-2-amine with diethyl 2-benzylidenemalonate [14,15] and 2-ethoxymethylidene-3-oxobutanenitrile [2] having three concurrent electrophilic reaction centers gave only one product, whereas two heterocyclic compounds were formed from ethyl 2-cyano-2-ethoxymethylidenepropionate [14] with participation of all three electrophilic centers. There are no published data on analogous transformations of fluoroalkyl-containing trielectrophiles.…”