Regioselective Alkylation of Heteroaromatic Compounds with 3-Methyl-2-Quinonyl Boronic Acids

Abstract

Reactions of heteroaromatic compounds with 3-methyl substituted 2-quinonyl boronic acids proceeded by 1,4-addition followed by spontaneous protodeboronation, leading directly to the Friedel-Crafts alkylation products instead of the commonly observed alkenylation derivatives resulting from quinones. The boronic acid acts as a temporary regiocontroller, making the system a highly reactive quinone equivalent and opening a direct access to 5,5-disubstituted cyclohexene-1,4-diones.

Electrochemical Properties of Substituted 2‐Methyl‐1,4‐Naphthoquinones: Redox Behavior Predictions

“…[8,14,19] However, there are not many versatile methods for the regioselective preparations of synthetic naphthoquinone derivatives bearing a methyl group at C2 of the quinone moiety (east) and substituted at the phenyl ring (west part) due to the dissymmetry of the (aza-)menadione molecule with its 2-methyl group. [20][21][22] For instance, the various combinations of the factors governing the regioselectivity of cycloadditions can produce highly selective and reactive effects; however, the results of these approaches depend on the structural features of the substrates, rendering the outcome of the reaction often unpredictable.…”

Mechanochemical Synthesis of N‐Aryl Amides from O‐Protected Hydroxamic Acids

“…A solution-based copper catalysed protodeboronation procedure under basic conditions was reported in 2014, [41] however, to the best of our knowledge, this is the first example of a mechanochemical protodeboronation reaction. Although historically protodeboronations have been considered of lesser importance by organic chemists, recently this reaction has found a variety of applications in synthetic procedures [42,43] and thus the aforementioned example may form a stepping stone for further development of such solventless protodeboronations. In general, protocol B gave slightly lower yields than protocol A, which can be rationalised since we know that side-reactions such as protodeboronations may occur, under protocol's B conditions.…”

A Two-Step Synthesis of a Novel 7,8-Dihydro-5,8-ethanoindolizine-6,9(5H)-dione

“…The best results were obtained when a mixture of PTSA and cerium chloride was used as a catalyst, giving a 40% yield of 9 after reaction for one hour in CH 2 Cl 2 (entry 15). Note, however, that even with this mixture of catalysts, the yield was low when the reaction was conducted in ethanol or MeCN (entries [17][18][19][20]. Mixing methanesulfonic acid (MSA) or HCl with CeCl 3 did not improve the yield markedly.…”

“…Compound 9 can also be obtained by a nucleophilic addition of pyrrole to (3,6-dimethyl-1,4-dioxo-1,4-dihydrobenzen-2-yl)boronic acid at -20°C; after spontaneous protodeboronation this gives rise to the heteroarylated product in 74% yield. 19 In this method, the presence of the -B(OH) 2 group in the substrate activates C-3 through the formation of a hydrogen bond with the neighboring carbonyl, which favors the nucleophilic addition of the heterocycle. Although this is an elegant reaction and its reported yield is higher than that of our method, the preparation of the boronic acid starting material is a laborious process that requires six synthetic stages.…”