Akhila K. Sahoo

Direct Access to Benzo[b]furans through Palladium-Catalyzed Oxidative Annulation of Phenols and Unactivated Internal Alkynes†

2,3-Disubstituted benzo[b]furans are prepared in one step from commercially available phenols and readily accessible unactivated internal alkynes (see scheme). This Pd-catalyzed oxidative annulation has a broad substrate scope and allows access to a wide range of benzo[b]furans.

Gold-Catalyzed Regioselective Hydration of Propargyl Acetates Assisted by a Neighboring Carbonyl Group: Access to α-Acyloxy Methyl Ketones and Synthesis of (±)-Actinopolymorphol B†

A general atom-economical approach for the synthesis of α-acyloxy methyl ketone is demonstrated through regioselective hydration of a wide range of propargyl acetates. Readily available catalyst comprising of 1% Ph(3)PAuCl and 1% AgSbF(6) in dioxane-H(2)O efficiently hydrolyzes the terminal alkynes of the propargyl acetate in the absence of acid promoters at ambient temperature within a short time. Effective regioselective hydration is facilitated by the neighboring carbonyl group as demonstrated through (18)O-labeling study. Compatibility of functional moieties and tolerance to various acid-labile protecting groups are observed. The catalytic condition is also suitable to perform hydration of TMS-substituted propargyl acetates, even though it requires prolonged reaction time for completion. Stereointegrity of the propargylic acetate is preserved during the hydration. The robustness of the system is successfully demonstrated through gram scale preparation of the product in nearly quantitative yield. The common α-acyloxy methyl ketone is transformed to 1,2-diol and 1,2-amino alcohol derivatives. Synthesis of actinopolymorphol B is achieved for the first time involving hydration of the propargyl acetate as the key step.

Sulfoximines: A Reusable Directing Group for Chemo‐ and Regioselective ortho CH Oxidation of Arenes

Sulfoximines direct: a new protocol for the chemo- and regioselective ortho C-H acetoxylation of arenes in N-benzoylated sulfoximines is reported. The sulfoximine directing group is easily detached from the C-H oxidation product through acid-promoted hydrolysis, isolated, and reused. The meta-substituted phenols are synthesized following this strategy and the stereointegrity of the sulfoximine is preserved in this transformation. C(sp(3))-H acetoxylation of the methyl group is also demonstrated.

Ru(II)-catalyzed intermolecular ortho-C–H amidation of aromatic ketones with sulfonyl azides

Ru(II)-catalyzed intermolecular ortho-C-H amidation of weakly coordinating aromatic ketones with sulfonyl azides is reported. The developed reaction protocol can be extended to various substituted aromatic ketones to afford a wide range of desired C-N bond formation products in good yields.

Gold-Catalyzed Intermolecular Hydrophenoxylation of Unactivated Internal Alkynes

A general and simple strategy for the synthesis of functionally diverse arylvinyl ethers is reported through gold-catalyzed intermolecular addition of electronically and sterically substituted phenols with unactivated alkynes. Addition of phenols to unsymmetrical alkynes provides the corresponding mixture of regioisomers with appreciable selectivity. Multiple hydrophenoxylations of polyphenols with diphenylacetylene are demonstrated successfully.

Synthesis of Thermally Stable Energetic 1,2,3‐Triazole Derivatives

Various thermally stable energetic polynitro-aryl-1,2,3-triazoles have been synthesized through Cu-catalyzed [3+2] cycloaddition reactions between their corresponding azides and alkynes, followed by nitration. These compounds were characterized by analytical and spectroscopic methods and the solid-state structures of most of these compounds have been determined by using X-ray diffraction techniques. Most of the polynitro-bearing triazole derivatives decomposed within the range 142-319 °C and their heats of formation and crystal densities were determined from computational studies. By using the Kamlet-Jacobs empirical relation, their detonation velocities and pressures were calculated from their heats of formation and crystal densities. Most of these newly synthesized compounds exhibited high positive heats of formation, good thermal stabilities, reasonable densities, and acceptable detonation properties that were comparable to those of TNT.

Ruthenium-Catalyzed Hydroarylation and One-Pot Twofold Unsymmetrical C-H Functionalization of Arenes.

A methyl phenyl sulfoximine (MPS) is used as a directing group in the ruthenium-catalyzed intramolecular hydroarylation of alkene-tethered benzoic acid derivatives to afford dihydrobenzofurans and indolines in good to excellent yields. A one-pot, unsymmetrical, twofold C-H functionalization involving intramolecular C-C and intermolecular C-C/C-N bond formations is successfully demonstrated by using a single set of catalytic reaction conditions, which is unprecedented thus far. A novel isoquinolone-bearing dihydrobenzofuran is constructed through an unsymmetrical twofold C-H functionalization.

Triazole‐Substituted Nitroarene Derivatives: Synthesis, Characterization, and Energetic Studies

A series of dense and energetic polynitroaryl-1,2,4-triazoles were synthesized through the nitration of aryl-1,2,4-triazoles. The Cu-catalyzed/base-mediated coupling reactions of haloarenes with 1,2,4-triazoles delivered N-aryl-1,2,4-triazoles. These new nitro-rich-aryltriazoles were characterized by analytical and spectroscopic methods. The solid-state structures of most of these compounds were established by X-ray diffraction analysis. Their thermal properties were determined by differential scanning calorimetry-thermogravimetric analysis. Their heats of formation (HOFs) and crystal densities were also calculated. The densities of the synthesized compounds ranged from 1.40 to 1.85 g cm(-3). Some of these newly synthesized compounds exhibited high positive HOFs, good thermal stabilities, high densities, and reasonable detonation velocities and pressures.

Regioselective hydration of terminal halo-substituted propargyl carboxylates by gold catalyst: synthesis of α-acyloxy α'-halo ketones.

Regioselective hydration of the terminal halo-substituted propargyl carboxylate by gold(I) catalyst is reported. The mild catalytic conditions tolerate common acid-labile protecting groups, and a wide variety of α-acyloxy α-halo ketones are efficiently synthesized within a short reaction time. The α-acyloxy α-halo ketones are used for the synthesis of 2-aminothiazoles.

Synthesis of trifluoromethyl-substituted N-aryl-poly-1,2,3-triazole derivatives

Synthesis, characterization, and physical properties of –CF3 and –NO2 substituted N-aryl-polytriazole derivatives are reported. The molecules are prepared by a reliable Cu-catalyzed [3 + 2]-cycloaddition between –CF3 substituted aryl azides and alkynes followed by a nitration sequence and also the base-promoted nucleophilic displacement of the halo groups by the 1,2,3-triazoles. The compounds are characterized by analytical and spectroscopic methods; the solid state structures of some of the compounds are confirmed by X-ray diffraction techniques. The synthesized materials decompose in the range of 195–308 °C. Most of the –CF3 and –NO2 groups-bearing aryl triazoles exhibit good densities and acceptable detonation characteristics. Some of the fluorine containing polytriazole-bearing compounds showed positive heats of formation.