Catalytic and direct methyl sulfonylation of alkenes and alkynes using a methyl sulfonyl radical generated from a DMSO, dioxygen and copper system

This paper describes an efficient method to β-keto methyl sulfones and (E)-vinyl methyl sulfones using DMSO as the substrate. The methyl sulfonyl radical generated from DMSO in the presence of catalytic Cu(I) under O2 atmosphere is believed to be involved in this reaction. Isotopic labeling and 18O2 experiments were performed to investigate the reaction mechanism.MOE (Min. of Education, S’pore)Accepted versio

Ruthenium- and rhodium-catalyzed cross-coupling reaction of acrylamides with alkenes : efficient access to (Z,E)-dienamides

Ruthenium- and rhodium-catalyzed direct oxidative cross-coupling reactions of acrylamides with alkenes were developed. These methods provide an efficient route for the synthesis of (Z,E)-dienamides in excellent yields with good stereoselectivity. The catalytic systems allowed oxidative olefination of a wide range of alkenes bearing different functional groups, such as CO2R, COMe, SO2Ph, aryl, CONHBn, CN, PO(OEt)2, as well as Weinreb amide

Asymmetric hetero-diels–alder reaction of Danishefsky’s dienes with α-carbonyl esters catalyzed by an indium(III)–PyBox complex

An efficient catalytic enantioselective hetero-Diels–Alder reaction of Danishefsky’s dienes with α-carbonyl esters using a chiral In(III)–pybox complex has been demonstrated. This protocol offers several advantages, including mild reaction conditions, relatively low catalyst loading, and good to excellent enantioselectivities. Furthermore, the absolute configurations of the new alkynyl-containing products were determined by CD spectra in combination with TD-DFT calculations

Asymmetric conjugate addition of grignard reagents to 3-silyl unsaturated esters for the facile preparation of enantioenriched β-silylcarbonyl compounds and allylic silanes

A highly enantioselective conjugate addition of Grignard reagents to 3-silyl unsaturated esters to deliver synthetically useful chiral β-silylcarbonyl compounds was developed. The synthetic value of this methodology was further illustrated by the synthesis of enantioenriched β-hydroxyl esters and the facile access granted to various α-chiral allylic silanes. A plethora of diastereoselective transformations of β-silylenolates were also investigated and afforded manifold organosilanes that contained contiguous stereogenic centers with excellent enantioselectivity

Copper-catalyzed olefinic trifluoromethylation of enamides at room temperature

Copper-catalyzed olefinic trifluoromethylation and oxytrifluoromethylation of enamides is reported. The direct olefinic C–H trifluoromethylation constitutes an efficient method for the stereoselective synthesis of β-trifluoromethyl substituted enamides

Rhodium-catalyzed C—H alkynylation of arenes at room temperature

The rhodium(III)-catalyzed ortho C[BOND]H alkynylation of non-electronically activated arenes is disclosed. This process features a straightforward and highly effective protocol for the synthesis of functionalized alkynes and represents the first example of merging a hypervalent iodine reagent with rhodium(III) catalysis. Notably, this reaction proceeds at room temperature, tolerates a variety of functional groups, and more importantly, exhibits high selectivity for monoalkynylation

Catalytic conversion of inert carbohydrates into platform chemical 5-hydroxymethylfurfural using arylboronic acids

Looking forward: As fossil fuels deplete, 5-hydroxymethylfurfural (HMF) will play an important role in securing future energy and chemical feedstock needs as it is obtainable from renewable resources such as glucose and cellulose. We report a group of nonmetal Lewis-acid arylboronic acids that catalyse the formation of HMF in 3-ethyl-1-methyl-3 H-imidazol-1-ium chloride ([EMIM]Cl) from glucose and cellulose. EWG=electron-withdrawing group

Macrolactam synthesis via ring-closing alkene-alkene cross-coupling reactions

Reported herein is a practical method for macrolactam synthesis via a Rh(III)-catalyzed ring closing alkene-alkene cross-coupling reaction. The reaction proceeded via a Rh-catalyzed alkenyl sp2 C-H activation process, which allows access to macrocyclic molecules of different ring sizes. Macrolactams containing a conjugated diene framework could be easily prepared in high chemoselectivities and Z,E stereoselectivities.Ministry of Education (MOE)Nanyang Technological UniversityThe authors gratefully acknowledge the financial support from the National Natural Science Foundation of China (No. 21702108), the Natural Science Foundation of Jiangsu Province, China (No. BK20160977), the Six Talent Peaks Project in Jiangsu Province (No. YY-033), Tier 1 grant M4012045.110 (No. RG12/18-S) from the Ministry of Education of Singapore and Distinguished University Professor grant, Nanyang Technological University, Singapore

Rhodium-catalysed C(sp2)–C(sp2) bond formation via C–H/C–F activation

Fluoroalkenes represent a class of privileged structural motifs, which found widespread use in medicinal chemistry. However, the synthetic access to fluoroalkenes was much underdeveloped with previous reported methods suffering from either low step economy or harsh reaction conditions. Here we present a RhIII-catalysed tandem C–H/C–F activation for the synthesis of (hetero)arylated monofluoroalkenes. The use of readily available gem-difluoroalkenes as electrophiles provides a highly efficient and operationally simple method for the introduction of α-fluoroalkenyl motifs onto (hetero)arenes under oxidant-free conditions. Furthermore, the employment of alcoholic solvent and the in-situ generated hydrogen fluoride are found to be beneficial in this transformation, indicating the possibility of the involvement of hydrogen bond activation mode with regards to the C–F bond cleavage step.Published versio