Mohammad Lokman Hossain

Formal carbene insertion into C-C bond: Rh(I)-catalyzed reaction of benzocyclobutenols with diazoesters.

A Rh(I)-catalyzed formal carbene insertion into C-C bond of benzocyclobutenols has been realized by employing diazoesters as carbene precursors. The product indanol derivatives were obtained in good yields and in diastereoselective manner under mild reaction conditions. All-carbon quaternary center is constructed at the carbenic carbon. This catalytic reaction involves selective cleavage of C-C bond, Rh(I) carbene insertion, and intramolecular aldol reaction.

CuI-Catalyzed Cross-Coupling of N-Tosylhydrazones with Terminal Alkynes: Synthesis of 1,3-Disubstituted Allenes

A CuI-catalyzed synthesis of 1,3-disubstituted allenes from 1-alkynes by the reaction with various N-tosylhydrazones has been developed. This method, which uses readily available starting materials and is operationally simple, offers 1,3-disubstituted allenes in moderate to good yields. The reaction also tolerates various functional groups.

Palladium-Catalyzed C-H Functionalization of Acyldiazomethane and Tandem Cross-Coupling Reactions

Palladium-catalyzed C-H functionalization of acyldiazomethanes with aryl iodides has been developed. This reaction is featured by the retention of the diazo functionality in the transformation, thus constituting a novel method for the introduction of diazo functionality to organic molecules. Consistent with the experimental results, the density functional theory (DFT) calculation indicates that the formation of Pd-carbene species in the catalytic cycle through dinitrogen extrusion from the palladium ethyl diazoacetate (Pd-EDA) complex is less favorable. The reaction instead proceeds through Ag2CO3 assisted deprotonation and subsequently reductive elimination to afford the products with diazo functionality remained. This C-H functionalization transformation can be further combined with the recently evolved palladium-catalyzed cross-coupling reaction of diazo compounds with aryl iodides to develop a tandem coupling process for the synthesis of α,α-diaryl esters. DFT calculation supports the involvement of Pd-carbene as reactive intermediate in the catalytic cycle, which goes through facile carbene migratory insertion with a low energy barrier (3.8 kcal/mol).

Synthesis of Allyl Allenes through Three-Component Cross-Coupling Reaction of N-Tosylhydrazones, Terminal Alkynes, and Allyl Halides

Threes a crowd: Tri- and tetrasubstituted allyl allenes can be easily accessed by this Cu(I)-catalyzed three-component coupling reaction of N-tosylhydrazones, terminal alkynes, and allyl halides. The reaction proceeds through a mechanism involving copper carbene migratory insertion.

Synthesis of Terminal Allenes through Copper-Mediated Cross-Coupling of Ethyne with N-Tosylhydrazones or α-Diazoesters

Ethyne is employed as coupling partner in copper-mediated cross-coupling reactions with N-tosylhydrazones and α-diazoacetate, leading to the development of a new synthetic method for terminal allenes. With this novel coupling method, the terminal allenes were obtained in good yields and with excellent functional group tolerance. Copper carbene migratory insertion is proposed as the key step in these transformations.

Synthesis of N-Containing Heterocyclic Compounds Using Visible-light Photoredox Catalysis

Nitrogen heterocycles represent a highly important class of compounds which are widely used in materials science, agrochemistry, and medicinal chemistry. Therefore, there is continuing interest in the development of convenient, efficient, and environmentally benign synthetic methods for the construction of nitrogen containing heterocycles. Due to its natural abundance, ease of use, and promising application in industry, the use of visible light as a driving force for chemical reactions has received considerable attention in the past few years. This account summarizes the synthesis of N-heterocycles using visible-light photoredox catalysis published in the last two years, according to the size and type of the formed N-heterocyclic rings. In the context of seminal works of others in this area, a concise summary of the contributions of the authors is also offered.

Cu(I)-catalyzed cascade reaction of N -tosylhydrazones with 3-butyn-1-ol: A new synthesis of tetrahydrofurans

Abstract The Cu(I)-catalyzed cascade coupling/cyclization reaction of N -tosylhydrazones with 3-butyn-1-ol has been explored. This new strategy represents a simple platform for the synthesis of tetrahydrofurans in moderate to good yields.

Cu(I)-Catalyzed Cross-Coupling of Diazo Compounds with Terminal Alkynes: An Efficient Access to Allenes

Cu(I)-catalyzed reaction of diazo compounds generates a Cu(I)-carbene intermediate that undergoes diverse transformations. In the past few years, the diazo compounds (or their precursor N-tosylhydrazones) have been established as cross-coupling partners under transition-metal catalysis, affording various organic compounds. Particularly the breakthrough has been made in allene synthesis by Cu(I)-catalyzed carbene coupling with terminal alkynes. Moreover, the Cu(I)-catalyzed coupling reaction of diazo compounds with terminal alkynes generates allene intermediate that undergoes tandem cyclization/coupling to afford cyclic compounds. This review article summarizes the most recent developments in allene synthesis based on the Cu(I)-carbene coupling reactions and the utilization of allene intermediates in tandem reactions.