Synthesis of indolo[1,2- c ]quinazolines from 2-alkynylaniline derivatives through Pd-catalyzed indole formation/cyclization with N , N -dimethylformamide dimethyl acetal

An efficient strategy for the synthesis of 6-unsubstituted indolo[1,2- ]quinazolines is described. The Pd-catalyzed reaction of -( -aminophenylethynyl) trifluoroacetanilides with Ar-B(OH) afforded 2-( -aminophenyl)-3-arylindoles, that were converted to 12-arylindolo[1,2- ]quinazolines by adding dimethylformamide dimethyl acetal (DMFDMA) to the reaction mixture after extractive work-up. This reaction outcome is different from the previously reported Pd-catalyzed sequential reaction of the same substrates with Ar-I, Ar-Br and ArN BF , that afforded 12-arylindolo[1,2- ]quinazolin-6(5 )-ones. Moreover, 12-unsubstituted indolo[1,2- ]quinazolines can be obtained both by reacting 2-( -aminophenyl)indoles with DMFDMA or by sequential Pd-catalyzed reaction of -( -aminophenylethynyl)aniline with DMFDMA.