Construction of Highly-Substituted Aromatics Bearing Acyl Substituents Using Cyclobutenedione Technology: Vinylketene-Based Benzannulations Using 3-Acyl-4-(substituted amino)cyclobutenediones

Article abstract of DOI:10.1021/jo00130a018

Highly-substituted acylated aromatics were efficiently synthesized from 3-acylcyclobutenediones via vinylketene-based benzannulations.Aryl and alkenyl lithiates added regioselectively to 3-acyl-4-(substituted amino)-3-cyclobutene-1,2-diones at -78 deg C to produce the corresponding 4-aryl- and 4-alkenyl-3-(substituted amino)-2-acylcyclobutenones in good yields.Substrates lacking the vinylogous functionality were not preparable by this route, because the acylcyclobutenedione starting materials are not sufficiently stable to manipulate.Benzannulations of 4-(3-furyl)-, 4-(2-thienyl)-, 4-(2-dihydropyranyl)-, 4-(2-dihydrofuranyl)-, 4-(1-naphthyl)-, and 4-(2-naphthyl)-substituted cyclobutenones proceeded in refluxing mesitylene to give the corresponding acyl aromatics in 80-90percent yield.Of all the 4-arylcyclobutenones synthesized (aryl = phenyl and substituted phenyl), only those with an electron-donating substituent (OMe, NMe2) at the meta position of phenyl group underwent benzannulation in refluxing mesitylene to afford acyl aromatics in moderate yields.