Synthesis of 2-anilinobenzimidates, anthranilamides, and 2, 3-dihydroquinazolin-4(1H)-ones from N-heterocyclic carbenes of indazole. Issue 2 (14th January 2015)

• Record Type: Journal Article
• Authors: Guan, Zong; Hillrichs, Kai; Ünlü, Cemre; Rissanen, Kari; Nieger, Martin; Schmidt, Andreas
• Is Part Of: Tetrahedron. Volume 71:Issue 2(2015)
• Page Start: 276
• Page End: 282
• Publication Date: 2015-01-14
• Subjects: Anthranilic acid -- Benzenecarboximidic acid -- Benzamide -- Carbene -- Indazol-3-ylidene; Chemistry, Organic -- Periodicals; 547.005
• DOI: 10.1016/j.tet.2014.11.054
• Languages: English
• ISSNs: 0040-4020

Abstract

Abstract: N -Heterocyclic carbenes of indazole (indazol-3-ylidenes), which are substituted at N1 with aromatics were generated in situ from the corresponding indazolium salts. At 60 °C the indazol-3-ylidenes underwent a ring-opening under N–N bond cleavage to intermediary N -(6-methylenecyclohexa-2, 4-dien-1-ylidene)anilines. Trapping of these intermediates by alcohols proved to be a convenient method for the preparation of 2-anilinobenzimidates, which have scarcely been described in the literature. The reaction temperature avoids carbene dimerization, which occurs at −80 °C or rearrangement of the ring-opened intermediate to acridines, which affords 100 °C. Water converted the ring-opened products into anthranilamides, which were cyclized on reaction with formaldehyde to 2, 3-dihydroquinazolin-4(1 H )-ones. Graphical abstract: