Synthesis Corner

DMSO as a C1 Building Block in the Co(III)-Catalyzed Synthesis of Quinolines

  Quinolines are common structural units in pharmaceuticals and other biologically-active compounds. Therefore, there are numerous named reactions to construct this motif (e.g., Skraup, Pfitzinger, etc.). As many of these reactions require harsh conditions and/or unusual starting materials, efforts have been made to develop milder methods using readily available starting materials with broader substrate scope. […]

DMSO-I2-Promoted Insertion of Isocyanide into the N–H Bond of Amines: Synthesis of Ureas

  Metal-catalyzed insertion reactions of isocyanides into amines have been developed with the ultimate goal of synthesizing nitrogen-containing heterocycles. These routes have had problems in that isocyanides often strongly coordinate to metal catalysts, and they often undergo polymerization under these conditions.1 Because of this, there is interest in developing metal-free methods. The metal-free insertion of […]

DMSO/I2-Catalyzed Functionalization of Cyclohexanones: Synthesis of Phenylenediamines

  N,Nʹ-Diaryl-o-phenylenediamines are precursors to many N-heterocyclic carbenes and are substructures of many medicinal substances, yet there are few routes to synthesize these compounds. This makes the metal-free method recently published by the Pan group particularly attractive.1 The method described by Pan’s group is simple, uses easily-acquired starting materials, and, with the use of the DMSO/I2 catalyst, is […]

Metal-, Photocatalyst, and Light-Free Alkylation of Heteroarenes and Quinones in DMSO

  Methods to perform late-stage C–H alkylations are highly valued because these reactions generally must be mild and tolerated by many substrates. Because of these constraints, often the scope of such reactions is limited. This makes the new metal-free, photocatalyst-, and light-free method described by the Lee group an important advance.1 All of the reagents/reactants […]

DMSO/I2: Simple and Green Syntheses of Imidazoles

  Imidazoles are crucial building blocks for many pharmaceuticals and agrichemicals.  Trisubstituted imidazoles are particularly important. Therefore, several methods have been developed to synthesize these structural units; however, these methods generally have several drawbacks, including the need for complex and harsh reaction conditions and toxic transition metal reagents. Additionally, they sometimes produce many side products. […]

Synthesis of Nitronaphthylamines using KOH/DMSO

  Amino and nitro-substituted naphthalenes are important structural units in pharmaceutical materials. Recently, the Verma group reported the first synthesis of nitronaphthylamines through a one pot reaction that involves an aza-Henry reaction followed by an annulation.1 This synthesis uses nitromethane in KOH/DMSO. This method can be extended to incorporate acetonitrile or benzophenone in place of nitromethane […]

Visible-Light-Induced Synthesis of Vinyl Sulfones from Cinnamic Acids in DMSO

  Dimethyl sulfoxide continues to be the solvent of choice for several light-induced reactions. (For other recent examples see Synthesis Corner posts from May 31, 2019, January 2, 2019, and October 1, 2018.) Recently Li and Wang demonstrated the light-induced synthesis of vinyl sulfones starting from various cinnamic acids and sodium arylsulfinates (Table 1).1 This reaction […]

DMSO/I2 Oxidation to Produce Heteroaromatic Aldehydes

  The oxidation methods using DMSO/I2 continue to grow. (For recent examples, see Synthesis Corner posts from January 6, 2020, October 31, 2019, and October 1, 2019.) These methods generally proceed through iodine-catalyzed C–H functionalization followed by a Kornblum-type oxidation at the same site. Along these lines, recent work by Chen et al. demonstrates the first […]

DMSO/I2-Mediated Synthesis of 3-Thiomethyl Chromones

  Chromones are important structural subunits in many natural products and biologically active compounds. Therefore, methods to synthesize or functionalize this structural motif are of high interest. The Wang and Wu group recently published their work where DMSO/I2 facilitates the three-component synthesis of chromones containing a thiomethyl group at the 3-position (3 in Table 1).1 This adds to […]

Visible-Light-Mediated Synthesis of γ-Ketoesters in DMSO

  γ-Ketoesters are common synthetic building blocks. Therefore, diverse synthetic methods have been developed to prepare these compounds. Recently, the Liu group reported a visible-light-mediated method, using compact fluorescent light (CFL), where the oxidative coupling of readily available vinylarenes and bromocarboxylates, followed by a Kornblum-type oxidation in DMSO, furnishes the desired γ-ketoester (equation in Table […]

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