Metal‐Free, Visible‐Light Promoted Intramolecular Azole C−H Bond Amination Using Catalytic Amount of I₂: A Route to 1,2,3‐Triazolo[1,5‐a]quinazolin‐5(4H)‐ones

Abstract

A metal-free, visible-light promoted intramolecular azole CÀ H bond amination for the rapid and efficient synthesis of pharmaceutical important 1,2,3-triazolo[1,5-a]quinazolin-5(4H)-ones has been developed. Employing 2-(1,2,3-triazol-1-yl)benzamides as the easily available precursors and catalytic amount of I 2 as an initiator, the desired product were isolated in moderate to excellent yiels with a broad substrate scope and good functional group tolerance. Furthermore, this protocol features mild conditions, operational simplicity, and easy scale-up. Preliminary mechanistic studies suggested that a radical pathway might be involved during the reaction.

Divergent cyclization of 2-(5-iodo-1,2,3-triazolyl)benzamides toward triazole-fused lactams and cyclic imidates

“…5 Thus, the common route, utilizing the thermal intramolecular Huisgen cycloaddition 6 (Scheme 1A-1), was augmented by interrupted CuAAC combined with Ullmann-type C–C coupling (Scheme 1A-2) 7 or oxidative 8 capture (Scheme 1A-3). Ag-, 9 Cu-, 10 and light/I 2 -mediated 11 radical cyclizations (Scheme 1A-4) have demonstrated their utility for the preparation of fused triazoles, containing C–N or C–O bonds, attached to the triazole ring. However, the most successful strategy involved Pd-catalyzed reactions (Scheme 1A-5): intramolecular Heck-type arylations, 12 carbonylative coupling 13 and isonitrile insertion, 14 cross-dehydrogenative coupling, 15 or Catellani reaction.…”

General Method of Synthesis of 5-(Het)arylamino-1,2,3-triazoles via Buchwald–Hartwig Reaction of 5-Amino- or 5-Halo-1,2,3-triazoles

“…The scope of the existing methods for the synthesis of these compounds is limited to a few examples and has a number of disadvantages. Thus, previously described methods for the preparation of 5-arylamino-1,2,3-triazoles include: (1) interaction between hard accessible carbodiimides and diazo compounds [ 21 ]; (2) three-component amine/enolizible ketone/azide reaction leading to low yields of the target products [ 33 ]; (3) high temperature thermolysis of the 5-triazenyl-1,2,3-triazoles to give a large amount of 2H-1,2,3-triazole as a by-product [ 34 ]; (4) base-mediated hydrolysis of 1,2,3-triazolo[1,5-a]quinazolin-5(4H)-ones [ 35 ] as well as Rh-catalyzed azide-alkyne cycloaddition of internal ynamides to afford N , N -disubstituted amino-1,2,3-triazoles [ 26 ].…”

Silver-Catalyzed Cascade Cyclization of Amino-NH-1,2,3-Triazoles with 2-Alkynylbenzaldehydes: An Access to Pentacyclic Fused Triazoles

“…In 2013, Shi et al [ 62 ] designed 4-( ortho -halo-aryl) 1,2,3-triazoles to merge with activated nitriles, forming a series of 5-amino-[1,2,3]triazolo-[5,1- a ]isoquinoline derivatives, a kind of valued tricyclic fused 1,2,3-triazoles ( Scheme 1 b). Though some achievements were reached in this field, there is still a lack of strategies for constructing interesting and complex fused 1,2,3-triazole derivatives, which attracts us considerably as we are persistently interested in this area [ 63 , 64 , 65 , 66 , 67 , 68 , 69 , 70 ]. Sparked by the vigorous performance of 2-alkynylbenzaldehyde in the synthesis of fused cyclic compounds [ 71 , 72 , 73 , 74 , 75 , 76 , 77 , 78 , 79 ], herein, we designed 2-(1 H -1,2,3-triazol-5-yl)anilines 1 to react with 2-alkynylbenzaldehydes 2 to construct isoquinolino [2,1- a ] [ 1 , 2 , 3 ] triazolo [1,5- c ] quinazolines 3 through a cascade process involving three C - N bond formations in one manipulation.…”