Phosphoryl- and thiophosphoryl-dithioformates. Part IV. Electrochemical reduction and EPR study of the radical anions †‡

Abstract

The reduction of a number of phosphoryl-and thiophosphoryl formates, monothioformates and dithioformates has been studied by means of cyclic voltammetry and EPR spectroscopy. The reduction potentials of all dithioformates are close to Ϫ1 V vs. SCE, and increase for S-alkyl monothioformates and even more for O-alkyl monothioformates. The radical anions of the compounds bearing the thiocarbonyl function have been characterised by means of EPR spectroscopy, whereas those of the compounds having the carbonyl function underwent decomposition before detection. Reduction at higher potentials led in most cases to the detection of paramagnetic dianions derived from fragmentation of the initially formed radical anions.

Redox‐Switchable Calix[6]arene‐Based Isomeric Rotaxanes

“…EPR spectra were recorded at room temperature with an ELEXYS E500 spectrometer equipped with an NMR gaussmeter for the calibration of the magnetic field and a frequency counter for the determination of g factors, which were corrected against that of the perylene radical cation in concentrated sulfuric acid ( g =2.002583). The electrochemical cell was homemade and consisted of an EPR flat cell (Wilmad WG‐810) equipped with a 25×5×0.2 mm platinum gauze (cathode), and a platinum wire (anode) . The current was supplied and controlled by an AMEL 2051 general‐purpose potentiostat.…”

“…The electrochemical cell was homemade and consisted of an EPR flat cell (Wilmad WG-810) equipped with a2 5 5 0.2 mm platinum gauze (cathode), and ap latinum wire (anode). [50,51] The current was supplied and controlled by an AMEL 2051 general-purpose potentiostat. In at ypical experiment, the cell was filled with an acetonitrile solution of the appropriate substrate (ca.…”

The difference in reactivity of (−)-mono and dimenthyl vs. diethyl alkylphosphonates in the α-lithiation reaction: Carbanionic synthesis of unknown (−)-dimenthyl 1-iodoalkylphosphonates and their first use in the radical iodine atom transfer addition (I-ATRA) and cyclisation (I-ATRC) reactions

“…of n-BuLi and the sterically more requiring LDA did not work in this case ( Table 1). The synthesis proceeded via the intermediate 1-silylated 1-iodoethylphosphonate (5), which in contrast to the diethyl series, turned out to be a stable compound, isolable by chromatography on silica gel (Scheme 2).…”

“…(À)-Dimenthyl phosphite was cyclized with 1,6-dienes under free radical conditions (AIBN) to give the cyclic product in 58% yields [3]. It was also employed in the condensation with carbon disulfide in the synthesis of (À)-dimenthyl phosphoryldithioformate and used in spin trapping [4], electrochemical and cyclic voltammetric reduction [5]. (À)-Dimenthyl phosphite as well as its sodium and ethylzinc salts were added by Kolodyazhnyi [6,7] to chiral C@N and C@C compounds as an example of efficient multistereoselectivity.…”

Remote electrochemical modulation of pK a in a rotaxane by co-conformational allostery

“…EPR spectra were recorded at room temperature using an ELEXYS E500 spectrometer equipped with an NMR gaussmeter for the calibration of the magnetic field and a frequency counter for the determination of g-factors that were corrected against that of the perylene radical cation in concentrated sulfuric acid (g = 2.002583). The homemade electrochemical cell consisted of an EPR flat cell (Wilmad WG-810) equipped with a 25-× 5-× 0.2-mm platinum gauze (cathode) and a platinum wire (anode) (47). The current was supplied and controlled by an AMEL 2051 general-purpose potentiostat.…”