Convenient method to obtain homoallylic thioethers from aromatic dithioacetal derivatives

Abstract

A new, convenient, and efficient method for the synthesis of homoallylic aromatic thioethers was developed. The present method consists of the formation of arylthionium intermediates from aromatic dithioacetals, which are trapped by a π-nucleophile. Screening of diverse aromatic substrates, selected Lewis acids, and allylstannane and allylsilane were evaluated. The method was found suitable for the preparation of homoallylic aryl thioethers bearing electron donating o-and p-groups only, as substrates with electron withdrawing groups were found unreactive to this system. Keywords Aromatic dithioacetals • Allylation • Lewis acid • Homoallyl sulfides Addition of π-nucleophiles to Lewis acids (LA)-activated carbonyl compounds or oxonium cations is one of the fundamental methods of construction of a new carbon-carbon bond (Yamamoto and Asao 1993; Masse and Panek 1995; Marshall 1996). As such, in a highly regioselective manner, in case of chiral substrates or catalysts with strong asymmetric induction, it is possible to obtain relevant alcohols or homoallylic ethers which are applicative building blocks in the synthesis of natural and biologically active products (Yus et al. 2013). Allyl metal reagents used in such process are allylborons, allylstannanes, allylsilanes, allyl halides, allyl acetates, allylindium (Yus et al. 2013; Shen et al. 2013; Kaib et al. 2016), or allyl transition metal complexes (e.g., Pd and Pt) that feature η 1-allyl or η 3-allyl bonding mode, respectively (Sone et al. 1995). Introduction of allyl function to the organic compounds gives opportunity for further double-bond transformations such as ozonolysis, epoxidation, dihydroxylation, cycloaddition hydroformylation, and olefin metathesis.

Hammett Correlation in Competing Fragmentations of Ionized 2‐Substituted Benzanilides Generated by Electron Ionization Mass Spectrometry

“…[8][9][10] The application of the Hammett equation was later extended to encompass other aspects of mass spectrometry. [11] Continuing contemporary interest in applying the Hammett equation to obtain insight into reaction mechanisms in a wide variety of contexts is illustrated by recent articles on its application in various fields including ion stability [12] and reaction mechanism, [13,14] and efforts to refine or generalise it. [15,16] One potential difficulty in constructing Hammett plots for the reaction of isolated ions is that acquiring conventional kinetic or thermodynamic data is not straightforward because there is no Maxwell-Boltzmann distribution of energy in the dissociating species generated in the dilute gas phase by electron ionization (EI) mass spectrometry.…”

“…The application of the Hammett equation was later extended to encompass other aspects of mass spectrometry [11] . Continuing contemporary interest in applying the Hammett equation to obtain insight into reaction mechanisms in a wide variety of contexts is illustrated by recent articles on its application in various fields including ion stability [12] and reaction mechanism, [13,14] and efforts to refine or generalise it [15,16] …”

Data enhanced Hammett-equation: reaction barriers in chemical space

“…This model is compelling since it gives an intuitive concept of electron donating and electron withdrawing effects [3][4][5][6] in the context of free energy differences. The model quickly became quite successful and has been applied to problems ranging from its original purpose, quantifying substituent effects, 3 to redox potentials, 7 dipole moments, 8 orbital energies of metallorganic complexes, 9 aromaticity, [10][11][12][13][14][15][16][17][18][19][20][21] ion stabilization, 22 mechanicistic investigation, 23,24 catalyst activity of nanoparticles, 25 proton-electron coupling in radicals, 26 molecular conductance, 27 excited singlet state, 28 and even toxicities. 29 More recent approaches have also tried to apply the models to nonbenzyl systems.…”

“…The Hammett equation, despite being studied and expanded during the last century, in order to encompass resonance [8], nucleophilicity [9], steric [10][11][12][13] and solvent effects [14][15][16][17][18][19], has been used almost exclusively in the field of reactions and substituent effects, mainly on benzene-like molecules, with the exception of studies on the correlation between Hammett parameters and other experimentally observed quantities [20][21][22][23]. However, such restriction is not imposed at any point by the Hammett equation and in a previous work [24] we showed how the model can be enhanced to be more robust, interpretable and general enough to encompass a wider area of the Chemical Compound Space (CCS).…”