Synthesis of Bicyclic Enediynes from Bis[phenyl[(trifluoromethanesulfonyl)oxy]iodo]acetylene: A Tandem Diels-Alder/Palladium(II)- and Copper(I)-Cocatalyzed Cross-Coupling Approach

Nickel-Catalyzed Amidation of Aryl Alkynyl Acids with Tetraalkylthiuram Disulfides: A Facile Synthesis of Aryl Alkynyl Amides

Nickel-catalyzed amidation of aryl alkynyl acids using tetraalkylthiuram disulfides as the amine source is described, affording a series of aryl alkynyl amides in good to excellent yields under mild conditions. This general methodology provides an alternative pathway for the synthesis of useful aryl alkynyl amides in an operationally simple manner, which shows its practical synthetic value in organic synthesis. The mechanism of this transformation was explored through control experiments and DFT calculations.

Intermolecular Diels-Alder Cycloaddition/Cross-Coupling Sequences of 2-Bromo-1,3-butadienes

2-Bromo-1,3-butadienes are demonstrated to be effective substrates for tandem Diels-Alder/transition metal cross-coupling reaction sequences. Intermolecular cycloaddition of a 2-bromo-1,3-diene with activated dienophiles proceeded under Lewis acid catalysis in generally high yields with good to excellent endo diastereoselectivity. The resulting vinyl bromide cycloadducts underwent subsequent Stille and Suzuki cross-couplings under standard conditions in good yields. Both the Diels-Alder and cross-coupling steps were highly tolerant of a range of functionalities and protecting groups. The use of the bromine substituent as both a cycloaddition directing group and cross-coupling nucleofuge avoids extra steps required to install and remove the more commonly used silyl enol ethers and enol sulfonates for each transformation and gives full control of the alkene regiochemistry throughout the reaction sequence. The 2-bromo-1,3-dienes were conveniently prepared in three steps from readily available aldehydes and established as hydrolytically stable and practical synthetic intermediates.

A novel sulfonamide non-classical carbenoid: a mechanistic study for the synthesis of enediynes

Alkynyl sulfonamides undergo sequential 1,4- then 1,2-addition/rearrangement with lithium acetylides to yield enediynes in the absence of any promoters or catalysts. Mechanistic investigations suggest that the reaction proceeds via 1,4-conjugate addition of the nucleophile to the unsaturated system to give a key alkenyl lithium species which is stabilised by an intramolecular coordination effect by a sulfonamide oxygen atom. This species can be considered a vinylidene carbenoid given the carbon atom bears both an anion (as a vinyllithium) and a leaving group (the sulfonamide). The intramolecular coordination effect serves to stabilise the vinyllithium but activates the sulfonamide motif towards nucleophilic attack by a second mole of acetylide. The resulting species can then undergo rearrangement to yield the enediyne framework in a single operation with concomitant loss of aminosulfinate.

Low Molecular Weight Norbornadiene Derivatives for Molecular Solar-Thermal Energy Storage

Molecular solar-thermal energy storage systems are based on molecular switches that reversibly convert solar energy into chemical energy. Herein, we report the synthesis, characterization, and computational evaluation of a series of low molecular weight (193-260 g mol(-1) ) norbornadiene-quadricyclane systems. The molecules feature cyano acceptor and ethynyl-substituted aromatic donor groups, leading to a good match with solar irradiation, quantitative photo-thermal conversion between the norbornadiene and quadricyclane, as well as high energy storage densities (396-629 kJ kg(-1) ). The spectroscopic properties and energy storage capability have been further evaluated through density functional theory calculations, which indicate that the ethynyl moiety plays a critical role in obtaining the high oscillator strengths seen for these molecules.

Palladium-Catalyzed Oxidative N-Dealkylation/Carbonylation of Tertiary Amines with Alkynes to α,β-Alkynylamides

The first highly effective Pd/C-catalyzed oxidative N-dealkylation/carbonylation of various aliphatic as well as cyclic tertiary amines with alkynes has been described. The selective sp(3) C-N bond activation of tertiary amines at the less steric side using O2 as a sole oxidant and a plausible reaction pathway for the reaction are discussed. The general and operationally simple methodology provides an alternative for the synthesis of a wide range of alk-2-ynamide derivatives under mild conditions. The present protocol is ecofriendly and practical, and it shows significant recyclability.

Pd-catalyzed aminocarbonylation of alkynes with amines using Co2(CO)8 as a carbonyl source

A facile protocol for aminocarbonylation of alkynes with amines at room temperature was developed using a metal carbonyl source.

On the reaction of 1,3-diphenylisobenzofuran and (2-iodoethynyl)(phenyl)iodonium triflate. A unique case of oxygen transfer from the Diels-Alder adduct to the diene

Reaction of 1,3-diphenylisobenzofuran (DPIBF) with 2-(iodoethynyl)(phenyl)-iodonium triflate at room temperature gave the expected Diels-Alder adduct, but using an excess of DFIBF (2 equiv.) and performing the reaction at 55 °C or heating at this temperature during the concentration stage, the initial orange solution or product mixture became dark brown and the products 1,2-phenylene-1,2-bis(phenylmethanone) and 2-(3-iodo-1,4-diphenylnaphthyl)(phenyl)iodonium triflate were obtained, which suggests an oxygen transfer between DPIBF and the initial adduct.

From solvolysis to self-assembly

My sojourn from classical physical-organic chemistry and solvolysis to self-assembly and supramolecular chemistry, over the last forty years, is described. My contributions to unsaturated reactive intermediates, namely vinyl cations and unsaturated carbenes, along with my decade-long involvement with polyvalent iodine chemistry, especially alkynyliodonium salts, as well as my more recent research with metal-ligand, coordination driven, and directed self-assembly of finite supramolecular ensembles are discussed.

Addition of benzylzinc halides to alkenyl(phenyl)iodonium triflates: stereoselective synthesis of trisubstituted alkenes

Benzylic organozinc reagents generated by insertion of zinc metal into benzyl-bromine bonds react with alkenyl(phenyl)iodonium triflates to provide single stereoisomers of trisubstituted olefins. The extremely high reactivity of the phenyliodonio moiety allows these reactions to be performed in the absence of copper salts or palladium catalysts. The reaction is performed from -40 degrees C to room temperature in THF. Excellent yields of the desired cross-coupled products have been obtained despite the occurrence of a competing electron-transfer-induced fragmentation.