Lewis Acid‐Catalyzed or Base‐Promoted Regioselective Cycloisomerization of N‐Imidoyl‐o‐alkynylanilines for Synthesis of N‐Imidoyl‐(1 H)‐indoles and 4‐Alkylidene‐3,4‐dihydroquinazolines

Abstract

Product selectivity control for the synthesis of imidoylindoles and 4-alkylidenedihydroquinazolines from N-imidoyl-o-alkynylanilines via silver triflate-catalyzedc ycloisomerization or tetrabutylammonium fluoride-promoted cyclization is described. Thep roduct selectivity depends mainly on the cata-lyst/promoteru sed, ando nt he substituents on the alkyne and amidinef unctionsoft he substrates.

Preparation of symmetrical C2-C2-linked bis- and tris-6-bromoindoles by Sonogashira couplings and 5-endo-dig cyclization induced by nBu4NF

“…The 5-endo-dig cyclization of ortho-alkynylaniline derivatives can be conducted by bases, [16][17][18][19][20][21][22] metals [23][24][25][26][27][28] and in the presence of electrophiles that can add functional groups to the indole nucleus. [29][30][31][32][33][34][35][36] In order to keep the procedure simple, the protocol using tetrabutylammonium fluoride (TBAF) 17,18 was chosen.…”

2‐(Alkynyl)anilines and Derivatives — Versatile Reagents for Heterocyclic Synthesis

“…Preliminarily prepared amidines 128 could be cyclized into quinazolines 129 under the treatment with silver triflate (10 mol%) (Scheme 41). [132] In this case, the substituent on N (3) prevents the formed ring from aromatization. Reactions of N‐unsubstituted‐2‐alkynylanilines, bearing COR group on triple bond with isocyanates and isothiocyanates gives 4‐ylydene substituted heterocycles respectively [133] …”

Annulation of 2‐Alkynylanilines: The Versatile Chemical Compounds

“…Ag(I)‐assisted annulation of 182 leads to the efficiently formation of 4‐methylidenequinazolines 183 (Scheme 57). [123] …”