Lanthanide-catalyzed cyclocarbonylation and cyclothiocarbonylation: a facile synthesis of benzannulated 1,3-diheteroatom five- and six-membered heterocycles

La[N(SiMe3)2]3 proves to be an efficient catalyst system for the cyclocarbonylation of 1,2-disubstituted benzenes with isocyanates. In this approach, aryl/alkyl isocyanates react with o-phenylenediamine, o-aminophenol, o-aminothiophenol, catechols and anilines ortho-substituted by CH2NH2 and CONH2 to form, respectively, the corresponding benzimidazolones, benzoxazolones, benzothiazolones, benzodioxolones, 3,4-dihydroquinazolin-2(1H)-one, and quinazolinediones. These results represent the first example of lanthanide-catalyzed carbonylation. This methodology is also applicable for the preparation of various benzannulated 1,3-diheteroatom cyclic thioketones starting from aryl/alkyl isothiocyanates or CS2 in good to excellent yields. Based on the results of experiments performed using an o-aminobenzamido dianion lanthanide complex, a general mechanism, involving the tandem reaction of two lanthanide-ligand bonds with one heterocumulene molecule, is proposed as well.