Quantitative structure-property relationships in the series of diazonium cations, intermediate products in the synthesis of analytical forms and dyes

Abstract

The azocoupling reaction of aromatic amines and phenols with aryldiazonium cations is of great importance for the production of dyes [1][2][3] and in analytical chemistry [4].Diazonium cations can be reduced either chemically or electrochemically [5][6][7][8][9][10][11][12]. For many compounds, the abilities to be subjected to electrophilic (nucleophilic) attack and to undergo oxidation (reduction) vary in parallel [13][14][15][16]. The susceptibility of diazo cations to reduction can serve as a measure of their electrophilic activity. Therefore, the a priori prediction of the reduction potentials and electron affinities of diazonium cations of the given structure and their subsequent directed synthesis is reasonable for the selection of the optimum reaction rates of the formation of azo dyes and analytical forms.Diazonium cations decompose to release molecular nitrogen [2,10,12,17]. To provide high yields of azo compounds and satisfactory accuracy, precision, and other performance characteristics of analytical procedures, it is desirable to avoid this competing reaction and to estimate quantitatively the degree of decomposition of newly synthesized diazonium salts.Among others, the stretching frequencies of the C -N + ≡ N group are a measure of the stability of diazonium cations (and simultaneously an indication of their activity as electrophilic agents) [17][18][19][20][21][22].As will be demonstrated below, vibrational frequencies and electron affinity correlate with the mesomeric dipole moments of substituents in aryldiazonium cations.The aim of this work was to find (based on quantumchemical calculations) quantitative structure-property relationships for the prediction of reduction potentials and some related quantities, electron affinities, stretching frequencies of the C -N + ≡ N group of aryldiazonium cations, and mesomeric dipole moments of groups of atoms.The correlations that are discussed in this work were presented in [23]. EXPERIMENTALCalculations were performed by the PM3 method [24] using the MOPAC program [25,26] with full geometry optimization (Broyden-Fletcher-GoldfarbShanno procedure [27]) using the Thiel algorithm for rapid minimization [28]. Preliminary optimization was performed by the molecular mechanics method (MMX procedure) [29] using the PCMODEL program [29]. In quantum-chemical calculations, we set the condition that the norm of the gradient was no higher than 0.084 kJ mol -1 Å -1 . In some cases, a sufficient decrease in the norm of the gradient was attained by the reject of Thiel rapid minimization (using the option NOTHIEL in the MOPAC program), by the optimization using the Davidon-Fletcher-Powell method (option DFP) [27], and by the combination of the approaches provided by the options NOTHIEL and DFP.For molecules with closed electronic shells, we used the restricted Hartree-Fock (RHF) method [26]. Radicals formed on the reduction of aryldiazonium salts were calculated by the unrestricted Hartree-Fock (UHF) method [26].Abstract -It was demonstrated that the reduction potentials,...

Diazotization-Enabled Deaminative Late-Stage Functionalization of Primary Sulfonamides

“…Nonetheless, the addition of radical inhibitors and trapping reagents, including 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO), 2,6-di- tert -butyl- p -hydroxytoluene (BHT), and 1,1-diphenyl ethylene (DPE), to the reaction systems of methods 1 and 2 did not significantly affect the reaction efficiencies (please see the Supporting Information, section 6.1). The kinetic experiments of diazotization using infrared spectroscopy showed that two distinct absorption peaks (2340 and 2360 cm –1 ) appear in the range of 2300–2400 cm –1 , which refer to the NN bond vibration, and their intensity increased as the reaction progressed (please see the Supporting Information, Figure S8c). An absorption band at 1457 cm –1 also occurs, which may correspond to the NN bond stretching mode (please see the Supporting Information, Figure S8d).…”