Unexpected Annulation between 2-Aminobenzyl Alcohols and Benzaldehydes in the Presence of DMSO: Regioselective Synthesis of Substituted Quinolines

Abstract

An unexpected annulation among 2-aminobenzyl alcohols, benzaldehydes, and DMSO to quinolines has been disclosed. For the reported annulation between 2-aminobenzyl alcohols and benzaldehydes, the change of the solvent from toluene to DMSO led to the change of the product from the diheteroatomic cyclic benzoxazines to monoheteroatomic cyclic quinolines. This annulation can be used to synthesize regioselectively different substituted quinolines by the choice of different 2-amino alcohols, aldehydes, and sulfoxides as substrates. Interestingly, introducing substituent groups to the α-position of sulfoxides resulted in the interchange of the positions between benzaldehydes and sulfoxides in the product quinolines. On the basis of the control experiments and literatures, a plausible mechanism for this annulation was proposed.

Biocatalytic and Chemo-Enzymatic Synthesis of Quinolines and 2-Quinolones by Monoamine Oxidase (MAO-N) and Horseradish Peroxidase (HRP) Biocatalysts

“…Oxidation is unarguably a fundamental transformation in synthetic chemistry and chemical industry, especially in accessing ubiquitous (hetero)­aromatic compounds . Despite endless attempts to improve the efficiency and practicality of this transformation, most of the traditional oxidation reactions heavily rely on transition-metal-catalyzed or promoted strategies or on the use of toxic reagents and harsh reaction conditions . From a sustainability point of view, the development of chemical processes that extend beyond the traditional oxidations is still highly desirable and remains a long-standing challenge in synthetic chemistry.…”

“… 1 Despite endless attempts to improve the efficiency and practicality of this transformation, most of the traditional oxidation reactions heavily rely on transition-metal-catalyzed or promoted strategies or on the use of toxic reagents and harsh reaction conditions. 2 From a sustainability point of view, the development of chemical processes that extend beyond the traditional oxidations is still highly desirable and remains a long-standing challenge in synthetic chemistry. The use of enzymes as catalysts in oxidations is of great appeal because of their mild, efficient, benign, and highly selective nature.…”

Nickel‐Catalyzed Sequential Dehydrogenation and Cyclization of 2‐Amino(Nitro)‐benzyl Alcohols with Alkyl Alcohols: Synthesis of C‐3‐Substituted Quinolines

“…3 ‐ (thiophen ‐ 2 ‐ yl)quinoline ( 3 f ) [17] . Following the general procedure A, the title product was obtained as a pale yellow liquid.…”

“…Yield: 42 %, (28 mg); 1 H NMR (500 MHz, Chloroform-d) δ 8.78 (d, J = 1.9 Hz, 1H), 8.07 (d, J = 8.3 Hz, 1H), 7.91 (s, 1H), 7.77 (d, J = 8.2 Hz, 1H), 7.65 (t, J = 7.7 Hz, 1H), 7.52 (t, J = 7.5 Hz, 1H), 2.80 (t, J = 7.7 Hz, 2H), 1.71 (d, J = 7.6 Hz, 2H), 1.26 (s, 14H), 0.88 (t, J = 6.9 Hz, 3H). ; 13 [17] Following the general procedure A, the title product was obtained as a white solid. Yield: 72 %, (39 mg); 1 H NMR (500 MHz, Chloroform-d) δ 9.04 (d, J = 2.…”

Regioselective Synthetic Approach to Higher Alkenes from Lower Alkenes with Sulfoxides in the Fe3+/H2O2 System via Direct Alkylation or Arylation of the Csp2–H Bond on the C═C Bond of Alkenes

“…Scientists have found that dimethyl sulfoxide (DMSO) is not only a commonly used solvent but also frequently serves as a versatile and commercially available reagent, so DMSO as a methyl reagent has great potential in organic synthesis and maybe could be applied to direct methylation of alkenes . Recently, the reactions between alkenes and DMSO have been reported a lot; these reactions could be mainly divided into the following categories: First, DMSO as a methyl donor participated in the difunctionalization of alkenes with nucleophiles .…”