Oxidative Conversion of α,α-Disubstituted Acetamides to Corresponding One-Carbon-Shorter Ketones Using Hypervalent Iodine (λ5) Reagents in Combination with Tetraethylammonium Bromide

Hypervalent iodine reagent-mediated reactions involving rearrangement processes

Hypervalent iodine reagents have been extensively employed in various types of oxidative organic reactions including oxidative coupling/cyclization, bifunctionalization of olefins and cyclopropane, C-H functionalization, and oxidative rearrangement reactions. In this review, the developments of the exclusive hypervalent iodine-mediated reactions involving oxidative rearrangement processes, including [1,2]-migration, Hofmann rearrangement, Beckmann rearrangement, ring contraction, ring expansion, [3,3]-sigmatropic/iodonium-Claisen rearrangement and some miscellaneous rearrangements, have been summarized.

One-pot method for the synthesis of 1-aryl-2-aminoalkanol derivatives from the corresponding amides or nitriles

We have identified a novel one-pot method for the synthesis of β-amino alcohols, which is based on C–H bond hydroxylation at the benzylic α-carbon atom with a subsequent nitrile or amide functional group reduction. This cascade process uses molecular oxygen as an oxidant and sodium bis(2-methoxyethoxy)aluminum hydride as a reductant. The substrate scope was examined on 30 entries and, although the respective products were provided in moderate yields only, the above simple protocol may serve as a direct and powerful entry to the sterically congested 1,2-amino alcohols that are difficult to prepare by other routes. The plausible mechanistic rationale for the observed results is given and the reaction was applied to a synthesis of a potentially bioactive target.

A one-pot method for β-amino alcohol synthesis based on α-hydroxylation and subsequent amide or nitrile functional group reduction has been identified and examined.

Selective C–C bond cleavage of amides fused to 8-aminoquinoline controlled by a catalyst and an oxidant

Herein, copper-catalyzed direct C–C bond cleavage of amides fused to 8-aminoquinoline as a directing group to form urea in the presence of amines and dioxygen is reported.

o-Iodoxybenzoic acid mediated generation of aryl free radicals: synthesis of stilbenes through C–C cross-coupling with β-nitrostyrenes

The generation of an aryl free radicals in the presence of nitrostyrenes through a combination of aryl hydrazines and o-iodoxybenzoic acid led to the synthesis of stilbenes by forming a new carbon–carbon bond after subsequent elimination of a nitrosyl radical.

Phenol Derivatives as Coupling Partners with Alkylsilicates in Photoredox/Nickel Dual Catalysis

Photoredox/nickel dual catalysis via single electron transmetalation allows coupling of Csp(3)-Csp(2) hybridized centers under mild conditions. A procedure for the coupling of electron-deficient aryl triflates, -tosylates, and -mesylates with alkylbis(catecholato)silicates is presented. This method represents the first example of the use of phenol derivatives as electrophilic coupling partners in photoredox/nickel dual catalysis.

Stereoselective synthesis of highly functionalized hydroindoles as building blocks for rostratins B-D and synthesis of the pentacyclic core of rostratin C

The stereoselective synthesis of a variety of functionalized hydroindoles suitable as building blocks for thiodiketopiperazine natural products such as rostratins B-D is reported. The key precursor for all transformations is a previously reported hexahydroindole compound. All functional groups were installed with the desired stereochemistry and the feasibility of the synthetic strategy was exemplified by dimerization of two hydroindole units to form the pentacyclic C2 -symmetric scaffold of rostratin C.

Unexpected dehomologation of primary alcohols to one-carbon shorter carboxylic acids using o-iodoxybenzoic acid (IBX)

IBX affords a novel, highly selective dehomologation of alcohols to their corresponding one-carbon shorter carboxylic acids.

2-Iodoxybenzoic Acid-Mediated Transformation of Halogenated Hydrocarbon in the Presence of Tetraethyl Ammonium Bromide

2-Iodoxybenzoic acid (IBX) has been shown to react with alkyl halides in the presence of tetraethyl ammonium bromide to give 2-iodobenzoate esters. Most of the monohalides and dihalides reacted easily with moderate to good yields. The 2-iodobenzoate esters containing other functional groups can offer further synthetic uses. The 2-iodobenzoic acid can be recycled easily and oxidised to IBX again.

Twist does a twist to the reactivity: stoichiometric and catalytic oxidations with twisted tetramethyl-IBX

The methyl groups in TetMe-IBX lower the activation energy corresponding to the rate-determining hypervalent twisting (theoretical calculations), and the steric relay between successive methyl groups twists the structure, which manifests in significant solubility in common organic solvents. Consequently, oxidations of alcohols and sulfides occur at room temperature in common organic solvents. In situ generation of the reactive TetMe-IBX from its precursor iodo-acid, i.e., 3,4,5,6-tetramethyl-2-iodobenzoic acid, in the presence of oxone as a co-oxidant facilitates the oxidation of diverse alcohols at room temperature.

Regioselective oxidation of cholic acid and its 7β epimer by using o-iodoxybenzoic acid

Rational exploration directed by DFT (density functional theory) based atomic Fukui indices, lead to development of regioselective oxidation of cholic acid and its 7β epimer by o-iodoxybenzoic acid. In case of cholic acid only, 7α-hydroxyl underwent oxidation, where as in its 7β epimer the selectivity was towards 12α-hydroxy group. Since these oxidations are the key steps in synthesis of ursodeoxycholic acid starting from cholic acid these findings may be useful in devising a protection free synthetic route.