Dehydrogenation of N‐Heterocyclic Compounds Using H₂O₂ and Mediated by Polar Solvents

Abstract

The oxidative dehydrogenation of N‐heterocyclic compounds by using H2O2 as oxidant in combination with polar solvents such as 1,1,1,3,3,3‐hexafluoroisopropanol (HFIP) and H2O is described. Among these two solvents, the best yields for the heteroaromatic compounds were generally achieved in HFIP. However, it is remarkable, that the use of a non toxic solvent such as H2O gave such good yields. Furthermore, the procedure was implemented in larger‐scale and HFIP was distilled from the reaction mixture and reused (up to 5 cycles) without a significant detriment in the reaction outcome.

Methyl 3,3-Bis[4-(dimethylamino)phenyl]-2,2-dimethylpropanoate

“…Citation: Mollà-Guerola, L.; Baeza, A. On the other hand, to continue our studies on the use of fluorinated alcohols as solvents and promoters of chemical transformations [2][3][4][5][6], we used fluoroalkyl alcohols to accomplish the above-mentioned transformation (Scheme 1). This idea arose not only because of the unique chemical and physical properties (such as a high hydrogen bond donor ability, low nucleophilicity, high polarity and ionizing power values and slight Brønsted acidity) of fluorinated alcohols [7][8][9], but also because they have both shown to promote nucleophilic substitution reactions onto the so-called activated alcohols (such as benzylic and allylic alcohols) [10] and activate silicon-based nucleophiles [11].…”

Cu-catalyzed aerobic oxidative dehydrogenation of tertiary indolines to indoles using azo/hydrazide redox

“…The dehydrogenation of saturated N-heterocycles to their corresponding N-heteroaromatic compounds is a fundamental and fascinating transformation in synthetic, materials, and medicinal chemistry. 1 The dehydrogenation of saturated N-heterocycles is conventionally conducted using stoichiometric amounts of oxidants such as DDQ, 2 metal oxides, 3 and others, 4 however, these methods are less attractive because of the toxicity and waste disposal associated with the oxidants. In recent years, transition metal-catalyzed acceptorless dehydrogenation has been regarded as a promising route for the synthesis of N-heteroaromatic compounds, 5 because acceptorless dehydrogenation requires no stoichiometric oxidants and produces only molecular hydrogen as a byproduct.…”