Cu-Catalyzed Dual C-O Bonds Cleavage of Cyclic Ethers with Carboxylic Acids, NaI, and TMSCF3 to Give Iodoalkyl Ester

Advances in the Synthetic Utility of Difluorocarbene Generated from TMSCF3 (Ruppert-Prakash Reagent) and Its Derivatives

Organofluorine compounds are of pivotal significance particularly, in drug and agrochemical industries and different strategies have been designed for their synthesis. The last two decades witnessed the emergence of difluorocarbene as an efficient synthetic tool, providing easy access to organofluorine compounds. This review summarises the reactions of difluorocarbene generated from Ruppert-Prakash reagent (TMSCF3) and its derivatives TMSCF2Cl and TMSCF2Br. Among the various fluorination techniques available, the difluorocarbene chemistry offers a cost effective and easy procedure, opening avenue to a large number of organofluorine compounds. This review details the developments in the utility of difluorocarbene generated from TMSCF3 and its derivatives, till date.

Carbene-induced ring-opening reactions of five-/six-membered cyclic ethers: expanding the frontiers of functional group introduction and molecular architecture construction

The multi-component ring-opening reactions of cyclic ethers offer an efficient strategy for the rapid introduction of multiple functional groups and the construction of complex molecular architectures. Despite the minimal ring strain in five- and six-membered rings presenting a significant challenge for ring-opening, advancements have been made. Traditional acid-catalyzed pathways have been complemented by a novel approach involving carbene-induced oxonium intermediate formation, which has emerged in recent years and expanded the selectivity of ring-opening reactions. This review outlines the evolution of carbene-induced ring-opening reactions of cyclic ethers over the past two decades, focusing on the development of carbene precursors and the pathways of carbene formation. The insights provided are anticipated to inform and inspire the creation of new carbene sources and the advancement of oxonium intermediates, thereby contributing to the field's progress.

Hydrogen Bond-Mediated Transition Metal-Free Alcoholysis of Primary Amides to Access Esters

An efficient hydrogen bond-mediated alcoholysis of primary amides was disclosed using diethyl phosphonate (DEP) as a catalyst. In this process, a wide range of primary amides and alcohols were tested and smoothly transformed to corresponding esters in moderate to good yields. This novel strategy features transition metal-free, broad substrate scope and a hydrogen bond-mediated one-pot pathway. In addition, the reaction showed a highly chemoselective o/alcoholic o-acylation of mercapto/phenolic alcohols.

Visible-Light-Induced Multi-Component Nitrooxylation Reactions of α-Diazoesters, Cyclic Ethers, and Tert-Butyl Nitrite Leading to Organic Nitrate Esters

A simple and efficient strategy has been developed for the synthesis of organic nitrate esters via visible-light-induced multi-component nitrooxylation reactions of α-diazoesters, cyclic ethers, and tert-butyl nitrite under open air atmosphere. This transformation could be conducted under mild and metal-free conditions to provide a number of organic nitrate esters in moderate to good yields using air as the green oxidant.

Visible Light-Assisted Ring-Opening of Cyclic Ethers with Carboxylic Acids Mediated by Triphenylphosphine and N-Halosuccinimides

The ring-opening of cyclic ethers (epoxide, oxetane, THF, and THP) by carboxylic acids was achieved by using N-iodosuccinimide (NIS) or N-bromosuccinimide (NBS) and triphenylphosphine under blue light. The corresponding ω-haloalkyl carboxylates were obtained under mild reaction conditions. The reaction is believed to work through a halogen bond complex between NIS (or NBS) and triphenylphosphine, which, upon irradiation with blue light, produces the key phosphine radical cation intermediate that initiates the ring-opening reactions.

Synthesis of 4-Alkylated 1,4-Dihydropyridines: Fe(II)-Mediated Oxidative Cascade Cyclization Reaction of Cyclic Ethers with Enaminones

Syntheses of highly functionalized 4-alkylated 1,4-dihydropyridines (1,4-DHPs) from cyclic ethers and enaminones via iron(II)-mediated oxidative free radical cascade C(sp3)-H bond functionalization/C(sp3)-O bond cleavage/cyclization reaction have been first developed. This novel synthetic strategy offers an alternative method for the construction of 1,4-DHPs by using esters as the C4 sources, as well as expands the application of ethers in heterocycle synthesis.

Copper-Catalyzed Cyclization of 2-Alkynylanilines to Give 2-Haloalkoxy-3-alkyl(aryl)quinolines

Herein we describe a method to produce 2-haloalkoxy-3-substituted quinolines via the cyclization of 2-alkynylanilines with TMSCF₃ and THF. This synthetic method uses inexpensive and easy-to-handle TMSCF₃ and employs a commercially available CuI catalyst to transform a broad range of 2-alkynylanilines into versatile 2-difluoromethoxy-3-substituted quinolines and 2-iodoalkoxy-3-substituted quinolines with excellent chemoselectivity.