4‐Hydroxycoumarin/2‐hydroxychromone tautomerism: Infrared spectra of 2‐¹³c and 3‐D labeled 4‐hydroxycoumarin and its anion

Abstract

Bands with primarily v (C=O) and v (C=O) character in the spectra of 4‐hydroxycoumarin and its anion were identified by isotopic substitution with either 13C or deuterium. Two bands of each type were found for spectra of 4‐hydroxycoumarin in solution in chloroform, dioxane, or dimethylsulfoxide, with v (C=O) at 1704–1733 cm−1 and ∼ 1567 cm−1. Two bands, at 1618 and 1559 cm−1, are associated with v (C=C) in the spectrum of crystalline 4‐hydroxycoumarin monohydrate, but only a single v (C=O) band at ∼ 1655 cm−1 was observed. Anhydrous 4‐hydroxycoumarin has v (C=O) bands at ∼ 1700 cm−1 and a shoulder at ∼ 1670 cm−1. The strong band at 1660 cm−1 in the spectrum of 4‐hydroxycommarin anion in dimethylsulfoxide solution is due to a delocalized v (O = C = O) vibration, whereas the band at 1555 cm−1 has partial v (C=C) character and involves C(3) but not C(2), supporting a fully delocalized char structure for the anion. No evidence for the existence of the 2‐hydroxychromone tautomer was found, except in the case of anhydrous 4‐hydroxycoumarin in the solid state.

Structure and ligand‐binding modes of human serum albumin studied by UV resonance raman spectroscopy

“…Since the UVRR spectrum of 4-hydroxycoumarin is similar to the spectrum A (data not shown), most of the bands observed are ascribed to the vibrations of the hydroxycoumarin part of the drug. IR spectra of a few isotope-labeled 4-hydroxycoumarins have been reported, 37 Figure 6 ( B ) , giving direct evidence that the Raman-intensity differences a t these wavenumbers arise from warfarin, and warfarin binds to a hydrophobic region of HSA. T h e remaining peak at stituted benzene derivatives, and they are assigned to the ring-stretching ( vSa) and CH-bending ( vga) modes of the benzene ring, respectively.…”

Organophosphorus chemistry 30 [1]. The behavior of 4-hydroxycoumarin toward methylenetriphenylphosphoranes (Wittig Reagents) and alkyl phosphites

“…This new approach is superior to that of other conventional procedures that either give poor yields of 11a,b or undesired by-products [3,4,13]. Apparently, 1 reacts with alkyl phosphites (3,4) more as a hydroxy compound [18,19] than as a lactone or cyclic ester [20].…”

“…Its ground-state structure (1A s 1B s 1C) has long been a subject of arguments [3][4][5]. During the initial chemical characterization of 1, it was recognized to be the enol tautomer of 2,4-chromandione (1B) [4].…”

“…4-Hydroxycoumarin (4HC, 1) comprises the structural nucleus of many natural products and pesticides [2,3]. Its ground-state structure (1A s 1B s 1C) has long been a subject of arguments [3][4][5].…”

Synthesis and cytotoxic activity of novel benzopyrano[3,2-c]chromene-6,8-dione derivatives

“…Introduction 4-Hydroxycoumarins constitute the structural nucleus of many natural products, drugs and pesticides (Feuer, 1974;Obaseki and Porter, 1982). They are the key intermediates for various widely used oral anticoagulants and rodenticides (Hermodson et al, 1971).…”