Cycloadditions. 24. Synthesis and reactions of sec. N-aryl-2,3-butadienamides

Article abstract of DOI:10.1002/prac.19963380169

The reaction of aryl isocyanates (1) with allenyl magnesium bromide (2) furnishes the sec. N-aryl-3-butynamides (4), which tend to tautomerize to the 2,3-butadienamides (5). Further heating of 5a-f (bearing benzoid nuclei) leads to decompositon, only 5g (bearing the naphthyl group) undergoes the expected intramolecular Diels-Alder (IMDA) reaction, leading to the benzo-tricycle (7g). By reaction of a second molecule isocyanate 1 the carbamoylation of the NH moiety of 5a, c and of 3g and 4g, resp. takes place. The thereby formed N-aryl-N-butadienoyl ureas (9) either cyclize to furnish the the N-carbamoyl-2-quinolones (10) or undergo the IMDA-reaction leading to the tricyclic compounds (11). The N-butadienoyl-N-(1-naphthyl)ureas (12) only furnish the IMDA-benzo-tricycles (13). Johann Ambrosius Barth 1996.