The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Amy R Howell - One of the best experts on this subject based on the ideXlab platform.
-
recent applications of oxetanes in the synthesis of heterocyclic compounds
Journal of Organic Chemistry, 2015Co-Authors: Christian A Malapit, Amy R HowellAbstract:Oxetanes are valuable intermediates in organic synthesis, and strategic manipulations of this strained heterocycle continue to emerge. In this Synopsis, recent, distinct approaches to construct heterocyclic systems using oxetanes are described. These include ring expansion, ring opening, and C-2 functionalization.
-
Silicon Acceleration of a Tandem Alkene Isomerization/Electrocyclic Ring‐Opening of 2‐Methyleneoxetanes to α,β‐Unsaturated Methylketones.
ChemInform, 2014Co-Authors: Elisa Farber, Aleksandra N. Rudnitskaya, Santosh Keshipeddy, Kendricks S. Lao, José A. Gascón, Amy R HowellAbstract:Heating of methyleneoxetanes is found to result in new, unexpected, and selective formation of methyl vinylketones via oxetene intermediates.
-
Silicon Acceleration of a Tandem Alkene Isomerization/Electrocyclic Ring-opening of 2-Methyleneoxetanes to α,β-Unsaturated Methylketones
The Journal of organic chemistry, 2013Co-Authors: Elisa Farber, Aleksandra N. Rudnitskaya, Santosh Keshipeddy, Kendricks S. Lao, José A. Gascón, Amy R HowellAbstract:The first rearrangement of 2-methyleneoxetanes to α,β-unsaturated methylketones is reported. It is proposed that when these substrates are heated, the corresponding Oxetenes are formed and subsequently undergo electrocyclic ring-opening to methyl vinylketones. In particular, α-silyl-α,β-unsaturated methylketones were isolated in moderate to high yields and with high stereoselectivities. Based on the proposed mechanism, density functional theory explains the differential kinetics and stereoselectivities among substrates.
-
Silicon Acceleration of a Tandem Alkene Isomerization/Electrocyclic Ring-opening of 2‑Methyleneoxetanes to α,β-Unsaturated Methylketones
2013Co-Authors: Elisa Farber, Santosh Keshipeddy, Kendricks S. Lao, Aleksandra Rudnitskaya, José A. Gascón, Amy R HowellAbstract:The first rearrangement of 2-methyleneoxetanes to α,β-unsaturated methylketones is reported. It is proposed that when these substrates are heated, the corresponding Oxetenes are formed and subsequently undergo electrocyclic ring-opening to methyl vinylketones. In particular, α-silyl-α,β-unsaturated methylketones were isolated in moderate to high yields and with high stereoselectivities. Based on the proposed mechanism, density functional theory explains the differential kinetics and stereoselectivities among substrates
-
2 alkylidene oxetanes by stereospecific elimination of mesylates
Tetrahedron Letters, 2007Co-Authors: Paul S Sabila, Amy R HowellAbstract:α-Mesyloxyoxetanes undergo stereospecific elimination to 2-alkylidene oxetanes upon treatment with potassium t-butoxide.
Sentaro Okamoto - One of the best experts on this subject based on the ideXlab platform.
-
Iron-Catalyzed Reductive Metalation–Allylation and Metalative Cyclization of 2,3-Disubstituted Oxetanes and Their Stereoselectivity
Synthesis, 2016Co-Authors: Yuki Sugiyama, Shiori Heigozono, Kazuhiro Tamura, Sentaro OkamotoAbstract:A novel process for the reductive magnesiation of 2-substituted oxetanes and the metalative cyclization of ω-alkynyl oxetanes is developed using n -propylmagnesium chloride in the presence of an iron catalyst. The generated intermediate organomagnesium compounds react with electrophiles. The reactions of 2,3-disubstituted oxetanes and their subsequent allylation with allyl halides in the presence or absence of copper(I) cyanide as the catalyst is studied with a unique switching of stereoselectivity being observed in the absence or presence of copper(I) cyanide . In addition, it is found that the metalative cyclization of 3-substituted 2-alkynyl oxetanes proceeds in an anti -selective manner starting from both syn - and anti -substrates. In all cases, the stereochemistry at the 2-position of the oxetanes is lost during the reactions suggesting the involvement of a radical process.
-
iron catalyzed reductive magnesiation of oxetanes to generate 3 oxidopropyl magnesium reagents
ChemInform, 2015Co-Authors: Yuki Sugiyama, Shiori Heigozono, Sentaro OkamotoAbstract:A facile method for the preparation of substituted 3-oxidopropylmagnesium compounds from 2- and 2,3-substituted oxetanes via a novel iron-catalyzed reductive magnesiation reaction is presented.
-
iron catalyzed reductive magnesiation of oxetanes to generate 3 oxidopropyl magnesium reagents
Organic Letters, 2014Co-Authors: Yuki Sugiyama, Shiori Heigozono, Sentaro OkamotoAbstract:In the presence of FeCln–(bisphosphine) or FeCln–(2-iminomethylpyridine) (n = 2 or 3), 2-substituted oxetanes reacted with Grignard reagents undergoing reductive magnesiation at the 2-position to afford substituted 3-oxidopropylmagnesium compounds, which are useful nucleophiles in reactions with a variety of electrophiles.
-
generation of a low valent titanium species from titanatrane and its catalytic reactions radical ring opening of oxetanes
ChemInform, 2014Co-Authors: Naoto Takekoshi, Kenji Miyashita, Noriaki Shoji, Sentaro OkamotoAbstract:The first examples of the C—O bond cleavage of various oxetanes at the 2-position using low valent titanium alkoxides, generated in situ from the titanatrane complex, Mg, and TmsCl, are presented.
James A Bull - One of the best experts on this subject based on the ideXlab platform.
-
short synthesis of oxetane and azetidine 3 aryl 3 carboxylic acid derivatives by selective furan oxidative cleavage
Organic Letters, 2020Co-Authors: Maryne A J Dubois, Milo A Smith, Andrew J P White, Alvin Lee Wei Jie, James J Mousseau, Chulho Choi, James A BullAbstract:Four-membered rings remain underexplored motifs despite offering attractive physicochemical properties for medicinal chemistry. Arylacetic acids bearing oxetanes, azetidines, and cyclobutanes are p...
-
2 sulfinyl oxetanes synthesis stability and reactivity
Synlett, 2015Co-Authors: Kate F Morgan, Ian A Hollingsworth, Rosemary A Croft, Robert Doran, James A BullAbstract:The synthesis of 2-sulfinyl oxetanes is described by a C–C bond-forming cyclisation strategy. Oxetanes bearing electron-poor aryl sulfoxides are shown to be viable targets using this strategy. We report investigations into the sulfoxide magnesium exchange on 2-sulfinyl oxetanes, which resulted in products formed via ligand exchange and ligand coupling pathways. The sulfinyl oxetanes can be readily oxidised to the sulfonyl oxetanes.
-
recent advances in the synthesis of 2 substituted oxetanes
Synlett, 2015Co-Authors: Owen A Davis, James A BullAbstract:Recent interest in oxetanes in medicinal chemistry and as synthetic intermediates has led to the development of a number of methods for the synthesis of more functionalized and highly substituted oxetane derivatives. Here we review cyclization approaches for the preparation of 2-substituted oxetanes. Methods involving C–O bond formation, as well as recently developed C–C bond forming cyclization strategies are highlighted.
-
Studies on the synthesis, stability and conformation of 2-sulfonyl-oxetane fragments
Organic & Biomolecular Chemistry, 2015Co-Authors: Kate F Morgan, Ian A Hollingsworth, James A BullAbstract:2-(Arylsulfonyl)oxetanes have been prepared as new structural motifs of interest for medicinal chemistry. These are designed to fit within fragment space and be suitable for screening in fragment based drug discovery, as well as being suitable for further elaboration or incorporation into drug-like compounds. The oxetane ring is constructed through an efficient C–C bond forming cyclisation which allows the incorporation of a wide range of aryl-sulfonyl groups. Furthermore, biaryl-containing compounds can be accessed through Suzuki–Miyaura coupling from halogenated derivatives. With a number of oxetane containing fragment compounds available, their pH stability was assessed, indicating good half-life values for mono-substituted aryl sulfonyl oxetanes across the pH range (1 to 10). Solubility and metabolic stability data is also reported. Finally, the conformation of the fragments is assessed computationally, providing an indication of possible binding orientations.
-
synthesis of di tri and tetrasubstituted oxetanes by rhodium catalyzed oh insertion and cc bond forming cyclization
Angewandte Chemie, 2014Co-Authors: Owen A Davis, James A BullAbstract:Oxetanes offer exciting potential as structural motifs and intermediates in drug discovery and materials science. Here an efficient strategy for the synthesis of oxetane rings incorporating pendant functional groups is described. A wide variety of oxetane 2,2-dicarboxylates were accessed in high yields, including functionalized 3-/4-aryl- and alkyl-substituted oxetanes and fused oxetane bicycles. Enantioenriched alcohols provided enantioenriched oxetanes with complete retention of configuration. The oxetane products were further derivatized, while the ring was maintained intact, thus highlighting their potential as building blocks for medicinal chemistry.
Koichi Mikami - One of the best experts on this subject based on the ideXlab platform.
-
mono di and trifluoroalkyl substituent effects on the torquoselectivities of cyclobutene and oxetene electrocyclic ring openings
Journal of Organic Chemistry, 2015Co-Authors: Kazuya Honda, Steven A. Lopez, K. N. Houk, Koichi MikamiAbstract:The reactivities and torquoselectivities of electrocyclic ring opening reactions of fluoromethyl-substituted cyclobutenes and Oxetenes were studied with M06-2X density functional theory. The torquoselectivities of a series of mono-, di-, and trifluoromethylcyclobutenes and Oxetenes result from the interplay of favorable orbital interactions and closed-shell repulsions. When the substituent rotates inward, there can be a favorable interaction between the breaking σ(CO) bond and the σ(CF)* orbital (σ(CO) → σ(CF)*) of the fluoromethyl group in fluoromethylOxetenes. The preference for rotation of a fluoromethyl group is decreased in trifluoromethylOxetenes because closed-shell repulsions between the breaking σ(CO) bond and trifluoromethyl substituent orbitals compete with the σ(CO) → σ(CF)* interaction.
-
Mono‑, Di‑, and Trifluoroalkyl Substituent Effects on the Torquoselectivities of Cyclobutene and Oxetene Electrocyclic Ring Openings
2015Co-Authors: Kazuya Honda, Steven A. Lopez, K. N. Houk, Koichi MikamiAbstract:The reactivities and torquoselectivities of electrocyclic ring opening reactions of fluoromethyl-substituted cyclobutenes and Oxetenes were studied with M06-2X density functional theory. The torquoselectivities of a series of mono-, di-, and trifluoromethylcyclobutenes and Oxetenes result from the interplay of favorable orbital interactions and closed-shell repulsions. When the substituent rotates inward, there can be a favorable interaction between the breaking σCO bond and the σCF* orbital (σCO → σCF*) of the fluoromethyl group in fluoromethylOxetenes. The preference for rotation of a fluoromethyl group is decreased in trifluoromethylOxetenes because closed-shell repulsions between the breaking σCO bond and trifluoromethyl substituent orbitals compete with the σCO → σCF* interaction
-
effect of the trifluoromethyl group on torquoselectivity in the 4π ring opening reaction of Oxetenes stereoselective synthesis of tetrasubstituted olefins
ChemInform, 2014Co-Authors: Kohsuke Aikawa, Natsumi Shimizu, Kazuya Honda, Yuta Hioki, Koichi MikamiAbstract:The highly stereoselective synthesis of tetrasubstituted olefins such as (II)/(III), (V), (VII)/(VIII), and (X)/(XI) bearing a CF3-group via the thermal 4π electrocyclic ring opening reaction of various Oxetenes is described.
-
Effect of the Trifluoromethyl Group on Torquoselectivity in the 4π Ring‐Opening Reaction of Oxetenes: Stereoselective Synthesis of Tetrasubstituted Olefins.
ChemInform, 2014Co-Authors: Kohsuke Aikawa, Natsumi Shimizu, Kazuya Honda, Yuta Hioki, Koichi MikamiAbstract:The highly stereoselective synthesis of tetrasubstituted olefins such as (II)/(III), (V), (VII)/(VIII), and (X)/(XI) bearing a CF3-group via the thermal 4π electrocyclic ring opening reaction of various Oxetenes is described.
-
Effect of the trifluoromethyl group on torquoselectivity in the 4π ring-opening reaction of Oxetenes: stereoselective synthesis of tetrasubstituted olefins
Chem. Sci., 2014Co-Authors: Kohsuke Aikawa, Natsumi Shimizu, Kazuya Honda, Yuta Hioki, Koichi MikamiAbstract:A highly stereoselective synthesis of tetrasubstituted olefins bearing a trifluoromethyl group via the thermal 4π electrocyclic ring-opening reaction of Oxetenes, simply prepared by the Pd-catalyzed [2+2] cycloaddition reaction of various alkynes with trifluoropyruvate, is achieved. In this reaction process, the trifluoromethyl group prefers inward rotational torquoselectivity because of the orbital interactions between the breaking C–O σ orbital on the oxetene moiety and the C–F σ* orbital in the transition state.
Yuki Sugiyama - One of the best experts on this subject based on the ideXlab platform.
-
Iron-Catalyzed Reductive Metalation–Allylation and Metalative Cyclization of 2,3-Disubstituted Oxetanes and Their Stereoselectivity
Synthesis, 2016Co-Authors: Yuki Sugiyama, Shiori Heigozono, Kazuhiro Tamura, Sentaro OkamotoAbstract:A novel process for the reductive magnesiation of 2-substituted oxetanes and the metalative cyclization of ω-alkynyl oxetanes is developed using n -propylmagnesium chloride in the presence of an iron catalyst. The generated intermediate organomagnesium compounds react with electrophiles. The reactions of 2,3-disubstituted oxetanes and their subsequent allylation with allyl halides in the presence or absence of copper(I) cyanide as the catalyst is studied with a unique switching of stereoselectivity being observed in the absence or presence of copper(I) cyanide . In addition, it is found that the metalative cyclization of 3-substituted 2-alkynyl oxetanes proceeds in an anti -selective manner starting from both syn - and anti -substrates. In all cases, the stereochemistry at the 2-position of the oxetanes is lost during the reactions suggesting the involvement of a radical process.
-
iron catalyzed reductive magnesiation of oxetanes to generate 3 oxidopropyl magnesium reagents
ChemInform, 2015Co-Authors: Yuki Sugiyama, Shiori Heigozono, Sentaro OkamotoAbstract:A facile method for the preparation of substituted 3-oxidopropylmagnesium compounds from 2- and 2,3-substituted oxetanes via a novel iron-catalyzed reductive magnesiation reaction is presented.
-
iron catalyzed reductive magnesiation of oxetanes to generate 3 oxidopropyl magnesium reagents
Organic Letters, 2014Co-Authors: Yuki Sugiyama, Shiori Heigozono, Sentaro OkamotoAbstract:In the presence of FeCln–(bisphosphine) or FeCln–(2-iminomethylpyridine) (n = 2 or 3), 2-substituted oxetanes reacted with Grignard reagents undergoing reductive magnesiation at the 2-position to afford substituted 3-oxidopropylmagnesium compounds, which are useful nucleophiles in reactions with a variety of electrophiles.
