Synthesis of Amines with Pendant Boronic Esters by Borrowing Hydrogen Catalysis

Amine alkylation reactions of alcohols have been performed in the presence of boronic ester groups to provide products which are known to have use as molecular sensors. The boronic ester moiety could be present in either the alcohol or amine starting material and was not compromised in the presence of a ruthenium catalyst

Iron-Catalyzed Methylation Using the Borrowing Hydrogen Approach

A general iron-catalyzed methylation has been developed using methanol as a C1 building block. This borrowing hydrogen approach employs a Knölker-type (cyclopentadienone)iron carbonyl complex as catalyst (2 mol %) and exhibits a broad reaction scope. A variety of ketones, indoles, oxindoles, amines, and sulfonamides undergo mono- or dimethylation in excellent isolated yields (>60 examples, 79% average yield)

<i>N</i>-Acyl DBN Tetraphenylborate Salts as <i>N</i>-Acylating Agents

Air-stable and crystalline <i>N</i>-acyl DBN tetraphenylborate salts have been synthesized from 1,5-diazabicyclo[4.3.0]­non-5-ene (DBN) and the corresponding acyl chloride in the presence of sodium tetraphenylborate. The salts have been shown to be effective <i>N</i>-acylating agents, reacting with primary amines, secondary amines, and sulfonamides to form the corresponding <i>N</i>-acylated products in good yields. The DBN hydrotetraphenylborate byproduct can be conveniently removed by filtration, providing pure <i>N</i>-acylated products without the need for further purification. The <i>N</i>-acyl DBN tetraphenylborate salts are attractive alternatives to acyl halides as they can be stored in air without decomposition, avoid the production of free acid during acylation reactions, and can be used under more forcing thermal conditions

Iodide as an Activating Agent for Acid Chlorides in Acylation Reactions

Acid chlorides can be activated using a simple iodide source to undergo nucleophilic attack from a variety of relatively weak nucleophiles. These include Friedel–Crafts acylation of <i>N</i>-methylpyrroles, <i>N</i>-acylation of sulfonamides, and acylation reactions of hindered phenol derivatives. The reaction is believed to proceed through a transient acid iodide intermediate

Synthesis of α,β-Unsaturated Aldehydes Based on a One-Pot Phase-Switch Dehydrogenative Cross-Coupling of Primary Alcohols

An efficient <i>one-pot</i> ruthenium-catalyzed hydrogen-transfer strategy for a direct access to α,β-unsaturated aldehydes has been developed. The employment of enolates prepared in situ from alcohols avoided handling unstable aldehydes and provided a very appealing route to different cinnamaldehydes substituted in position 2. A silica-grafted amine was used as phase-switch tag leading to a selective one-pot process in favor of cross-dehydrogenative coupling products

Exploring Tandem Ruthenium-Catalyzed Hydrogen Transfer and S_NAr Chemistry

A hydrogen-transfer strategy for the catalytic functionalization of benzylic alcohols via electronic arene activation, accessing a diverse range of bespoke diaryl ethers and aryl amines in excellent isolated yields (38 examples, 70% average yield), is reported. Taking advantage of the hydrogen-transfer approach, the oxidation level of the functionalized products can be selected by judicious choice of simple and inexpensive additives