Transition-Metal-Free Cross-Dehydrogenative Coupling of Triazines with 5,7-Dihydroxycoumarins

Abstract

A new method for the direct metal-free C-H functionalization of electron-deficient triazines with fragments of naturally occurring and synthetic 5,7-dihydroxycoumarins is reported. It has been found that the reaction of 5,7-dihydroxycoumarins with triazines proceeds under mild conditions, showing a high chemo-and regioselectivity.

Crystal structure of 4-(3-fluorophenyl)-7-hydroxy-2H-chromen-2-one, C15H9FO3

“…The dihedral angle between the two units was found to be 127.28(4)°and 129.7(1)°, respectively. All bond parameters are comparable to closely related compounds in literature [15][16][17][18][19][20][21]. Neighbouring molecules are joined together via classical intermolecular O-H• • • O hydrogen bonds between the hydroxyl and carbonyl groups.…”

MnO2-Mediated Oxidative Cyclization of “Formal” Schiff’s Bases: Easy Access to Diverse Naphthofuro-Annulated Triazines

“…In a continuation of our research on CDC reactions in triazines [ 54 , 67 ] and diazines [ 68 ], herein, we are pleased to report an unusual synthesis of benzofuro-fused 1,2,4-triazines via the sequence of C-C/C-O CDC reactions of 1,2,4-triazines with 2-naphthols or phenols ( Scheme 1 d). The reaction proceeded through the formation of 1,4-dihydrotriazine, followed by oxidative cyclization.…”

Cross‐Dehydrogenative Coupling Reactions between Phenols and Hetarenes: Modern Trends in Cross‐Coupling Chemistry of Phenols

“…However, in the case of pteridin-4-one (R=H), the oxidative coupling products were obtained in moderate yields via a one-step reaction involving TFA. [91] Khalymbadzha et al [92] showed that 5,7-dihydroxycoumarins can undergo nucleophilic addition to sand as-triazines in the same manner as diazines [91] to form stable σ H -adducts in yields of up to 97%. p-Chloranil enabled the aromatisation of the dihydrotriazine σ H -adducts, affording the oxidative coupling products in good yields.…”

“…Khalymbadzha et al [92] . showed that 5,7‐dihydroxycoumarins can undergo nucleophilic addition to s ‐ and as ‐triazines in the same manner as diazines [91] to form stable σ H ‐adducts in yields of up to 97%.…”