Michael R. Emmett

Bio: Michael R. Emmett is an academic researcher from University of Western Ontario. The author has contributed to research in topics: Cyclopropane & Nucleophile. The author has an hindex of 5, co-authored 9 publications receiving 512 citations. Previous affiliations of Michael R. Emmett include University College West.

Carbocycles from donor–acceptor cyclopropanes

Abstract: This review summarizes research directed towards the formation of carbocyclic adducts from donor–acceptor cyclopropanes. The focus of the review is on annulation and cycloaddition reactions (both inter- and intramolecularly) mediated by Lewis or protic acid, bases, or thermal conditions. Rearrangements resulting in carbocycles and those reactions mediated by transition metal catalysis have been excluded.

Tandem ring-opening decarboxylation of cyclopropane hemimalonates with sodium azide: a short route to γ-aminobutyric acid esters.

Abstract: Cyclopropane hemimalonates, when treated with sodium azide, undergo a tandem ring-opening decarboxylation to produce γ-azidobutyric acids in good yields. These adducts were hydrogenated to form γ-aminobutyric acid (GABA) methyl esters.

Catalyst-Free Tandem Ring-Opening/Click Reaction of Acetylene-Bearing Donor–Acceptor Cyclopropanes

Abstract: Cyclopropane-1,1-hemimalonates bearing a 2-(2-alkynylphenyl) moiety underwent ring opening by an azide nucleophile, generating an alkyl azide that, in turn, underwent [3+2]-dipolar cycloaddition with the alkyne. The products are novel linearly fused tricyclic 1,2,3-triazoles.

A new golden age for donor-acceptor cyclopropanes.

Abstract: The effective use of ring strain has been applied to considerable advantage for the construction of complex systems. The focus here is directed towards cyclopropanes as building blocks for organic synthesis. Although thermodynamics should take the side of synthetic chemists, only a specific substitution pattern at the cyclopropane ring allows for particularly mild, efficient, and selective transformations. The required decrease in the activation barrier is achieved by the combined effects of vicinal electron-donating and electron-accepting moieties. This Review highlights the appropriate tools for successfully employing donor–acceptor cyclopropanes in ring-opening reactions, cycloadditions, and rearrangements.

Development of Synthetic Methodologies via Catalytic Enantioselective Synthesis of 3,3-Disubstituted Oxindoles

Abstract: Conspectus3,3-Disubstituted oxindoles are widely distributed in natural products, drugs, and pharmaceutically active compounds. The absolute configuration and the substituents on the fully substituted C3 stereocenter of the oxindole often significantly influence the biological activity. Therefore, tremendous efforts have made to develop catalytic enantioselective syntheses of this prominent structural motif. Research in this area is further fueled by the ever-increasing demand for modern probe- and drug-discovery programs for synthetic libraries of chiral compounds that are derived from privileged scaffolds with high structural diversity. Notably, the efficient construction of fully substituted C3 stereocenters of oxindole, tetrasubstituted or all-carbon quaternary, spirocyclic or not, also becomes a test ground for new synthetic methodologies.We have been engaged in developing efficient methods for diversity-oriented synthesis of chiral 3,3-disubstituted oxindoles from readily available starting material...

Ein neues goldenes Zeitalter in der Chemie Donor‐Akzeptor‐substituierter Cyclopropane

Abstract: Ringspannung gewinnbringend zu nutzen, ist seit jeher fur den Aufbau komplexer Systeme von grosem Vorteil. Schnell richtet sich somit der Blick auf Cyclopropane als Bausteine fur die organische Synthese. Auch wenn die Thermodynamik dabei auf der Seite des Synthesechemikers steht, ermoglicht erst ein spezielles Substitutionsmuster am Cyclopropan besonders milde, effiziente und selektive Umsetzungen. Die erforderliche Absenkung der Aktivierungsbarriere wird durch die Kombination von zueinander vicinal stehendem Elektronendonor und -akzeptor erreicht. Dieser Aufsatz beleuchtet die richtigen Hilfsmittel, um mit Donor-Akzeptor-substituierten Cyclopropanen Ringoffnungen, Cycloadditionen und Umlagerungen durchzufuhren.

Advances in Stereoconvergent Catalysis from 2005 to 2015: Transition-Metal-Mediated Stereoablative Reactions, Dynamic Kinetic Resolutions, and Dynamic Kinetic Asymmetric Transformations

Abstract: Stereoconvergent catalysis is an important subset of asymmetric synthesis that encompasses stereoablative transformations, dynamic kinetic resolutions, and dynamic kinetic asymmetric transformations. Initially, only enzymes were known to catalyze dynamic kinetic processes, but recently various synthetic catalysts have been developed. This Review summarizes major advances in nonenzymatic, transition-metal-promoted dynamic asymmetric transformations reported between 2005 and 2015.

Catalytic Enantioselective Ring-Opening Reactions of Cyclopropanes.

Abstract: This review describes the development of enantioselective methods for the ring opening of cyclopropanes. Both approaches based on the reaction of nonchiral cyclopropanes and (dynamic) kinetic resolutions and asymmetric transformations of chiral substrates are presented. The review is organized according to substrate classes, starting by the more mature field of donor-acceptor cyclopropanes. Emerging methods for enantioselective ring opening of acceptor- or donor-only cyclopropanes are then presented. The last part of the review describes the ring opening of more reactive three-membered rings substituted with unsaturations with a particular focus on vinylcyclopropanes, alkylidenecyclopropanes, and vinylidenecyclopropanes. In the last two decades, the field has grown from a proof of concept stage to a broad range of methods for accessing enantioenriched building blocks, and further extensive developments can be expected in the future.