Catalytic Amount Of Iodine Research Articles

A novel and easy protocol to obtain 6-alkoxy-Δ4,6-diene-3-one derivatives from available sterols

Herein we report an unprecedented and efficient methodology for accessing 6-alkoxy-Δ4,6-diene-3-one derivatives. Such scaffolds were serendipitously obtained in the course of the study of the reaction of Δ4-3-keto steroids with catalytic amounts of iodine in refluxing methanol. A series of 6-methoxy and 6-ethoxy- Δ4,6-diene-3-ones were prepared from easily-available sterols in a two-step sequence; first, oxidation of sterols furnished the Δ4-3-keto steroids, which were then refluxed with ethanol or methanol with I2 as catalyst to obtain a series of ten derivatives. Furthermore, this protocol was also effective for the introduction of a larger carbon chain at C-6. Druglikeliness properties of synthesized compounds were predicted using the SwissADME tool.

Visible-Light-Driven Iodine-Catalyzed Synthesis of Unsymmetrical Disulfides via Oxidative Coupling

AbstractHerein, a facile and environmentally friendly oxidative coupling reaction to obtain unsymmetrical disulfide compounds, without using metal or organic dyes as photocatalyst and only using a catalytic amount of iodine, was developed. Oxygen is used as oxidant in the reaction and the substrate scope is wide. A gram-scale synthesis also highlights the synthetic practicality of this photochemical strategy. Moreover, our mechanistic studies support the formation of disulfide products through free-radical coupling.

Iodine‐Catalysed Reactions of Aroylmethylidenes: Efficient Access to α‐Substituted Aryl Ketones, Functionalized Naphthofurans and Highly Functionalized Pyrroles

AbstractAn efficient and facile iodine‐catalysed approach has been established for the formation of α‐substituted aryl ketones and valuable substituted naphthofurans. Under the same reaction conditions, a series of highly functionalized pyrroles could be readily obtained. This metal‐free and environmentally friendly reaction proceeded very well and delivered the products in good to excellent yields. This work highlights the formation of α‐substituted aryl ketones, naphthofuran and pentasubstituted pyrrole derivatives under catalytic amount of iodine in one‐pot fashion, demonstrating the broad substrate scope.

One-pot and metal-free synthesis of 3-arylated-4-nitrophenols via polyfunctionalized cyclohexanones from β-nitrostyrenes.

β-Nitrostyrenes underwent a Diels–Alder reaction with Danishefsky’s diene to afford cyclohexenes together with the corresponding hydrolyzed products, 3-arylated-5-methoxy-4-nitrocyclohexanones. When the reaction was conducted in the presence of water, the cyclohexenes were efficiently hydrolyzed into cyclohexanones. Subsequent aromatization by heating the cyclohexanone with a catalytic amount of iodine in dimethyl sulfoxide gave 3-arylated-4-nitrophenols. The reaction of nitrostyrenes with Danishefsky’s diene could be conducted in one pot to directly afford the corresponding nitrophenols. Moreover, a heteroaryl group, e.g., a thienyl group could be introduced into the nitrophenol framework.

Metal-Free Halogen(I) Catalysts for the Oxidation of Aryl(heteroaryl)methanes to Ketones or Esters: Selectivity Control by Halogen Bonding.

Metal-free halogen(I) catalysts were used for the selective oxidation of aryl(heteroaryl)methanes [C(sp3 )-H] to ketones [C(sp2 )=O] or esters [C(sp3 )-O]. The synthesis of ketones was performed with a catalytic amount of NBS in DMSO solvent. Experimental studies and density functional theory (DFT) calculations supported the formation of halogen bonding (XB) between the heteroarene and N-bromosuccinimide, which enabled imine-enamine tautomerism of the substrates. No additional activator was required for this crucial step. Isotope-labeling and other supporting experiments suggested that a Kornblum-type oxidation with DMSO and aerobic oxygenation with molecular oxygen took place simultaneously. A background XB-assisted electron transfer between the heteroarenes and halogen(I) catalysts was responsible for the formation of heterobenzylic radicals and, thus, the aerobic oxygenation. For selective acyloxylation (ester formation), a catalytic amount of iodine was employed with tert-butyl hydroperoxide in aliphatic carboxylic acid solvent. Several control reactions, spectroscopic studies, and Time-Dependent Density Functional Theory (TD-DFT) calculations established the presence of acetyl hypoiodite as an active halogen(I) species in the acetoxylation process. With the help of a selectivity study, for the first time we report that the strength of the XB interaction and the frontier orbital mixing between the substrates and acyl hypoiodites determined the extent of the background electron-transfer process and, thus, the selectivity of the reaction.

Synthesis of Dodecaallylhexasilacyclohexane and Its Convertibility

Dodecaallylhexasilacyclohexane 4, which would be a stable precursor for a variety of hexasilacyclohexane derivatives, was synthesized by the reaction of [pedeta·SiH2Cl]2[Si6Cl12·2Cl] (1) with allylmagnesium bromide. In addition, an effective synthetic route of dodecachlorohexasilacyclohexane 3 from trichlorosilane was found. Deallylmethoxylation of 4 with catalytic amount of iodine and methanol yielded dodecamethoxyhexasilacyclohexane 5 almost quantitatively, but was found to be highly sensitive toward water. Herein, we report the first spectroscopical and structural data of 5.

(2R,3R)-3-[(1R)-1-{[tert-Butyl(dimethyl)silyl]oxy}ethyl]-4-oxoazetidin-2-yl Acetate in Zinc- and Samarium-Promoted Substitution Reactions with Methyl 2-Bromopropanoate and Methyl (2-Bromomethyl)prop-2-enoate. Unusual Cleavage of the N1‒C4 Bond in Azetidin-2-one Derivative with Migration of Methoxycarbonyl Group in Synthetic Approaches to Carbapenems and Their Analogs

The use of zinc in Barbier-type reactions of (2R,3R)-3-[(1R)-1-{[tert-butyl(dimethyl)silyl]oxy}-ethyl]-4-oxoazetidin-2-yl acetates with halogen derivatives led to the formation of expected substitution products. The reaction of the title compound with a reagent prepared from samarium powder, a catalytic amount of iodine, and methyl 2-bromopropanoate in THF gave an anomalous substitution product, methyl 2-{(2S,3S)-3-[(1R)-1-{[tert-butyl(dimethyl)silyl]oxy}ethyl]-4-oxoazetidin-2-yl}-2(R,S)-methyl-3-oxopentanoate. Alkylation of the latter with methyl bromoacetate afforded methyl 2-{(2S,3S)-3-[(1R)-1-{[tert-butyl(dimethyl) silyl]oxy}ethyl]-1-(2-methoxy-2-oxoethyl)-4-oxoazetidin-2-yl}-2(RS)-methyl-3-oxopentanoate which underwent fragmentation through cleavage of the N1–C4 bond under the action of sodium bis(trimethylsilyl)-amide in THF at–78°C. The resulting acyclic amide, dimethyl {(2R,S,3Z)-2-[(1R)-1-{[tert-butyl(dimethyl)-silyl]oxy}ethyl)]-4-methyl-5-oxohept-3-enoylamino}malonate, was smoothly converted to new functionalized N-substituted pyrrolidinones via intramolecular Michael type cyclization in methylene chloride in the presence of NEt3–DMAP–Boc2O.

Iodine-Catalyzed Chemoselective Hydroamination Reaction Using 5-Mercaptotetrazoles Derivatives.

Metal-free chemoselective hydroamination of styrene derivatives has been achieved with high chemoselectivity over sulfenylation of 1H-tetrazole-5-thiol using a catalytic amount of iodine. The scope of this methodology has been extended for the hydroamination of α-substituted styrene derivatives. This reaction involves a single-step C–N-bond formation under atom economical process. This eco-friendly method uses readily available and inexpensive iodine in a catalytic amount.

Mechanochemical synthesis of N-tert-butanesulfinyl imines under metal-free conditions

A simple and convenient mechanochemical method for the condensation of aldehydes with tert-butanesulfinamide using catalytic amounts of iodine under metal- and solvent-free conditions is described.

Microwave assisted metal-/oxidant-free cascade electrophilic sulfenylation/5-endo-dig cyclization of 2-alkynylanilines to generate diversified 3-sulfenylindoles

A metal-/oxidant-free sustainable protocol for the synthesis of 3-sulfenylindoles based on electrophilic cyclization of 2-alkynylanilines has been developed under microwave irradiation. Herein, catalytic amount of iodine and stoichiometric amount of sulfonyl hydrazides were employed as catalyst and electrophiles respectively to induce the 5-endo-dig cyclization of 2-alkynylanilines. This strategy allows a wide substrate scope, demonstrates good functional group tolerance, utilizes easily available reagents and overcome multistep synthesis.

O-Iodoxybenzoic Acid (IBX)–Iodine Mediated One-Pot Deacylative Sulfonylation of 1,3-Dicarbonyl Compounds: A Synthesis of β-Carbonyl Sulfones

A combination of o-iodoxybenzoic acid (IBX) and a catalytic amount of iodine is found to promote a facile one-pot deacylative sulfonylation reaction of 1,3-dicarbonyl compounds with sodium sulfinates to yield β-carbonyl sulfones. The present method provides the target products bearing a wide variety of functional groups in one step and in good yields.

Synthesis of trimethylsilyl carboxylates by HMDS under solvent-free conditions

A broad set of structurally different carboxylic acids were transformed into their trimethylsilyl esters with HMDS in a practically completely solvent-free process, while a catalytic amount of iodine was required in some cases. The process has several advantages over the known methods: untreated reactants, air atmosphere, mild and neutral conditions, no evolution of hydrogen halide, no need of an additional base, low amount of waste, completely without chromatography, low consumption of energy, and operational simplicity.

Iodine-Catalyzed Direct Olefination of 2-Oxindoles and Alkenes via Cross-Dehydrogenative Coupling (CDC) in Air.

A direct intermolecular olefination of sp(3) C-H bond between 2-oxindoles and simple alkenes via a Cross-Dehydrogenative Coupling (CDC) strategy has been developed. In the absence of additional base, moderate to excellent yields have been obtained by using a catalytic amount of iodine with atmospheric oxygen as the reoxidant. Based on the observation of a radical capture experiment, the transformation is proposed to proceed via a radical process.

Iodine/TBHP

In recent times, several advancements were made in using catalytic amounts of iodine in combination with tert-butyl hydroperoxide (TBHP) as co-oxidant. The increased utility is mainly due to its inexpensive, environmentally benign nature, good efficiency and compatibility to work in place of rare or toxic heavy metal oxidants.[1] The I2/TBHP catalytic system works efficiently for numerous C–C and C–X (X = heteroatom) bond-forming organic transformations under mild reaction conditions to offer the desired products in excellent yields.[2]

ChemInform Abstract: A Novel Lanthanum Metal‐Assisted Reaction of Diaryl Ketones and Electrophiles.

Abstract A novel and efficient lanthanum metal-assisted carbon-carbon bond formation of diaryl ketones and various electrophiles, such as carbonyl compounds, esters, nitriles, and epoxides, has been developed. When diaryl ketones were allowed to react with dialkyl ketones in the presence of lanthanum metal and a catalytic amount of iodine, the cross pinacol coupling reaction proceeded to give the corresponding unsymmetrical 1,2-diols in moderate to good yields. α-Hydroxy ketones were prepared by the lanthanum metal-assisted reaction of diaryl ketones with esters or nitriles, followed by hydrolysis with aq HCl. It is interesting to note that for the epoxides, the coupling reaction proceeded via the Meinwald rearrangement of epoxides to give the corresponding 1,2-diols.

ChemInform Abstract: Hypoiodite‐Mediated Catalytic Cyclopropanation of Alkenes with Malononitrile.

AbstractHypoiodite species are generated from catalytic amounts of iodine and the terminal oxidant tBuOOH.

Aerobic photooxidative synthesis of 2-aryl-4-quinazolinones from aromatic aldehydes and aminobenzamide using catalytic amounts of molecular iodine

This study reports a safe, mild, and environmentally benign synthetic method toward 2-aryl-4-quinazolinones through a cyclization–oxidation sequence using a catalytic amount of iodine, harmless visible light irradiation, and molecular oxygen.

A novel lanthanum metal-assisted reaction of diaryl ketones and electrophiles

A novel and efficient lanthanum metal-assisted carbon-carbon bond formation of diaryl ketones and various electrophiles, such as carbonyl compounds, esters, nitriles, and epoxides, has been developed. When diaryl ketones were allowed to react with dialkyl ketones in the presence of lanthanum metal and a catalytic amount of iodine, the cross pinacol coupling reaction proceeded to give the corresponding unsymmetrical 1,2-diols in moderate to good yields. α-Hydroxy ketones were prepared by the lanthanum metal-assisted reaction of diaryl ketones with esters or nitriles, followed by hydrolysis with aq HCl. It is interesting to note that for the epoxides, the coupling reaction proceeded via the Meinwald rearrangement of epoxides to give the corresponding 1,2-diols.

ChemInform Abstract: A General Metal Free Approach to α‐Ketoamides via Oxidative Amidation—Diketonization of Terminal Alkynes.

AbstractIn the presence of trimethylsilyl triflate and catalytic amounts of iodine, the first metal free oxidative amidation—diketonization of terminal alkynes leads to a wide variety of α‐ketoamides.

New Synthesis of β-Anilinochalcones by Regioselective Oxidation of β-Anilinodihydrochalcones Using Iodine–DMSO

β-Anilinodihydrochalcones readily undergo oxidation α to the carbonyl group region in the presence of a catalytic amount of iodine in dimethyl sulfoxide at 130 °C in good yield. Oxidation of allyloxy-substituted β-anilinodihydrochalcones to β-anilinochalcones is a preferred reaction over deallylation.