A mild and chemoselective method for deprotection of aryl acetates and benzoates under non-hydrolytic condition

Cleavage of Carboxylic Esters by Aluminum and Iodine

A one-pot procedure for deprotecting carboxylic esters under nonhydrolytic conditions is described. Typical alkyl carboxylates are readily deblocked to the carboxylic acids by the action of aluminum powder and iodine in anhydrous acetonitrile. Cleavage of lactones affords the corresponding ω-iodoalkylcarboxylic acids. Aryl acetylates undergo deacetylation with the participation of the neighboring group. This method enables the selective cleavage of alkyl carboxylic esters in the presence of aryl esters.

Iridium-Catalyzed C-H Amination of Weinreb Amides: A Facile Pathway toward Anilines and Quinazolin-2,4-diones

C-H amination of arenes directed by weakly coordinating Weinreb amides has been achieved with an iridium catalyst and 2,2,2-trichloroethoxycarbonyl (Troc) azide as an aminating agent, providing a robust method of producing synthetic useful ortho-TrocNH aryl Weinreb amides. Taking advantage of the reactivity of Weinreb amide and Troc groups in the amination products, selective hydrolysis was achieved as an attractive process for the synthesis of ortho-NH₂ aryl Weinreb amides, which are the building blocks useful in the synthesis of bioactive compounds, and cascade aminocyclization with primary amines was successful and provided an efficient pathway for the construction of quinazolin-2,4-diones, which are present in various alkaloids and natural products.

P2O5 / SiO2 as a mild and efficient reagent for acylation of alcohols, phenols and amines under solvent-free conditions

P2O5 / SiO2 is a highly efficient reagent for the acetylations of a variety of alcohols, phenols and amines with acetic anhydride under solvent-free conditions. Primary, secondary, allylic and benzylic alcohols, diols and phenols with electron-donating or withdrawing substituents can be easily acetylated in good to excellent yield.

CSJ acting as a versatile highly efficient greener resource for organic transformations

We have reported the simple, new, greener biotransformation for the selective reduction of aromatic aldehydes, decarboxylation of aromatic acids and hydrolysis of aromatic compounds by Cucumis sativus L. juice (CSJ).

Synchronous double C–N bond formation via C–H activation for a novel synthetic route to phenazine

Pd–Ag binary nanocluster-catalysed synchronous double C–N bond formationviaC–H activation during self-coupling of anilines to form phenazines.

The palladium and copper contrast: a twist to products of different chemotypes and altered mechanistic pathways

Unprecedented Pd–Ag/Cu–Ag nanocluster-catalyst switch leads to a phenazine/azoarene twist for non-radical mode C–H activation vs. radical mode N–N self-coupling of anilines.

ZrCl4 as an efficient catalyst for a novel one-pot protection/deprotection synthetic methodology

A catalytic quantity of ZrCl 4 (20 mol %) was found to be an efficient catalyst for the one-pot esterification and deprotection of (5 S,6 R)-5,6-diacetoxyoct-7-enoic acid in good yields (44-62%) with a lactone formed as a minor byproduct. ZrCl 4 (10-20 mol %) was also sufficient to deprotect 1,3-dioxalane, bis-TBDMS ethers, and diacetate functional groups in excellent yields of up to 93%. ZrCl 4 (1-10 mol %) also promoted diol protection as the acetonide in 90% yield and acted as a trans-esterification catalyst for a range of esters.

Aminolysis of Y-Substituted Phenyl X-Substituted Benzoates with Piperidine: Effect of Nonleaving Group Substituent

The title reaction has been suggested to proceed through a zwitterionic tetrahedral intermediate with a change in the rate determining step on the basis of the curved Brønsted-type plots obtained. The curvature center of the curved Brønsted-type plots is at pKa = 6.4 regardless of the electronic nature of the substituent X in the benzoyl moiety.

Structure–reactivity correlations in nucleophilic substitution reactions of Y-substituted phenyl X-substituted benzoates with anionic and neutral nucleophiles

A kinetic study is reported for the reactions of 4-nitrophenyl X-substituted benzoates (1a-1) and Y-substituted phenyl benzoates (2a-1) with two anionic nucleophiles (OH(-) and CN(-)) and three amines (piperidine, hydrazine, and glycylglycine) in 80 mol% H(2)O-20 mol% dimethyl sulfoxide (DMSO) at 25.0 +/- 0.1 degrees C. Each Hammett plot exhibits two intersecting straight lines for the reactions of 1a-1 with the anionic nucleophiles and piperidine, while the Yukawa-Tsuno plots for the same reactions are linear. The Hammett plots for the reactions of 2a-1 with hydrazine and glycylglycine demonstrate much better linear correlations with sigma(-) constants than with sigma degrees or sigma constants, indicating that the leaving group departure occurs at the rate determining step (RDS). On the contrary, sigma(-) constants result in poorer Hammett correlation than sigma degrees constants for the corresponding reactions with OH(-) and CN(-), indicating that the leaving group departure occurs after the RDS for the reactions with the anionic nucleophiles. The large rho(X) value (1.7 +/- 0.1) obtained for the reactions of 1a-1 with the anionic nucleophiles supports the proposal that the reactions proceed through an addition intermediate with its formation being the RDS.

Perchloric acid adsorbed on silica gel as a new, highly efficient, and versatile catalyst for acetylation of phenols, thiols, alcohols, and amines

Perchloric acid adsorbed on silica gel efficiently catalyses acetylation of structurally diverse phenols, alcohols, thiols, and amines under solvent free conditions.

Reinterpretation of curved Hammett plots in reaction of nucleophiles with aryl benzoates: change in rate-determining step or mechanism versus ground-state stabilization

A kinetic study is reported for the reaction of the anionic nucleophiles OH-, CN-, and N 3 - with aryl benzoates containing substituents on the benzoyl as well as the aryloxy moiety, in 80 mol % H2O - 20 mol % dimethyl sulfoxide at 25.0 degrees C. Hammett log k vs sigma plots for these systems are consistently nonlinear. However, a possible traditional explanation in terms of a mechanism involving a tetrahedral intermediate with curvature resulting from a change in rate-determining step is considered but rejected. The proposed explanation involves ground-state stabilization through resonance interaction between the benzoyl substituent and the electrophilic carbonyl center in the two-stage mechanism. Accordingly, the data are nicely accommodated on the basis of the Yukawa-Tsuno equation, which gives linear plots for all three nuceophiles. Literature reports of the mechanism of acyl transfer processes are reconsidered in this light.