The Experts below are selected from a list of 261 Experts worldwide ranked by ideXlab platform
Michael Shipman - One of the best experts on this subject based on the ideXlab platform.
-
Regio- and Stereocontrolled Synthesis of 3‑Substituted 1,2-Diazetidines by Asymmetric Allylic Amination of Vinyl Epoxide
2017Co-Authors: Sundaram Rajkumar, Guy J. Clarkson, Michael ShipmanAbstract:Pd-catalyzed asymmetric allylic amination of rac-vinyl epoxide with unsymmetrical 1,2-hydrazines proceeds with excellent regio- and stereocontrol, which after further ring closure provides differentially protected 3-vinyl-1,2-Diazetidines in good yields. The chirality at C-3 exerts stereocontrol over the nitrogen centers in the 1,2-Diazetidine with all substituents orientating themselves trans to their neighbors. Efficient functionalization without rupture of the strained ring is demonstrated (e.g., by cross-metathesis), establishing the first general route to C-3-substituted 1,2-Diazetidines in enantioenriched form
-
Synthesis of 4,5-Diazaspiro[2.3]hexanes and 1,2-Diazaspiro[3.3]heptanes as Hexahydropyridazine Analogues
2017Co-Authors: Alpa K. Pancholi, Guy J. Clarkson, Greg P. Iacobini, David W. Porter, Michael ShipmanAbstract:4,5-Diazaspiro[2.3]hexanes are made by dihalocarbene addition across the exocyclic double bond of readily accessible 3-alkylidene-1,2-Diazetidines. Using difluorocarbene, generated from TMSCF3/NaI, these spirocycles were produced in yields up to 97% by stereospecific addition across the alkene. Lower yields (up to 64%) were observed using more reactive dichlorocarbene, due to competitive insertion of the carbene into the N–N bond. Larger 1,2-diazaspiro[3.3]heptanes are produced by [2 + 2] cycloaddition of 3-alkylidene-1,2-Diazetidines with tetracyanoethylene (TCNE) in up to 99% yield
-
Chemo- and enantioselective Rh-catalysed hydrogenation of 3-methylene-1,2-Diazetidines: application to vicinal diamine synthesis
Chemical communications (Cambridge England), 2012Co-Authors: Greg Iacobini, David Porter, Michael ShipmanAbstract:Rhodium catalysed hydrogenation of 3-methylene-1,2-Diazetidines with a range of chiral ligands is reported. Using Mandyphos, excellent levels of chemo- and enantioselectivity (up to 89% ee) can be achieved. Reductive cleavage of the derived 3-substituted 1,2-Diazetidine with LiDBB provides the enantioenriched biscarbamate protected 1,2-diamine.
-
Chemo- and Enantioselective Rh-Catalyzed Hydrogenation of Methylene-1,2-Diazetidines for the Synthesis of Vicinal Diamines
2012Co-Authors: David Porter, Michael Shipman, Greg IacobiniAbstract:Rhodium catalyzed hydrogenation of methylene-1,2-Diazetidines with a range of chiral ligands is reported. Using Mandyphos, excellent levels of chemo- and enantioselectivity (up to 89%ee) are achieved. Reductive cleavage of the resultant 3-substituted 1,2-Diazetidine with LiDBB yields the biscarbamate protected 1,2-diamine without racemisation.
-
Synthesis and functionalization of 3-alkylidene-1,2-Diazetidines using transition metal catalysis
Organic letters, 2011Co-Authors: Michael J. Brown, Guy J. Clarkson, Graham G. A. Inglis, Michael ShipmanAbstract:An efficient two-step synthesis of a wide range of 3-methylene-1,2-Diazetidines has been developed through application of a Cu(I)-catalyzed 4-exo ring closure. The double bond of this new class of strained heterocycle can be functionalized in a stereocontrolled manner by using palladium-catalyzed Heck reactions. Moreover, chemoselective reduction of 3-alkylidene-1,2-Diazetidines gives access to saturated 1,2-Diazetidines and vicinal diamines.
Kevin E. O'shea - One of the best experts on this subject based on the ideXlab platform.
-
The reaction of N-methyl-1,2,4-triazoline-3,5-dione with tetracyclopropylethylene. Formation of an unusual meso-ionic product and its rearrangement to the Diazetidine.
Journal of the American Chemical Society, 2004Co-Authors: Duk Kyung Kim, Kevin E. O'sheaAbstract:The reaction of N-methyl-1,2,4-triazoline-3,5-dione and tetracyclopropylethylene results in the quantitative formation of a meso-ionic compound. The formation of this unusual compound is likely the result of the unique conformational and steric properties of the cyclopropyl groups which inhibit the expected reaction pathways. The meso-ionic compound undergoes an unprecedented rearrangement to the Diazetidine upon warming to 55 °C.
Dongmao Zhang - One of the best experts on this subject based on the ideXlab platform.
-
Synthesis of C-Unsubstituted 1,2-Diazetidines and Their Ring-Opening Reactions via Selective N-N Bond Cleavage.
The Journal of organic chemistry, 2018Co-Authors: Hetti Handi Chaminda Lakmal, Bassem Ahmed, Christopher Fong, David J. Szalda, Keith Ramig, Andrzej Sygula, Charles Edwin Webster, Dongmao ZhangAbstract:C-Unsubstituted 1,2-Diazetidines, a rarely studied type of four-membered heterocyclic compounds, were synthesized through an operationally simple intermolecular vicinal disubstitution reaction. 1,2-Diazetidine derivatives bearing various N-arylsulfonyl groups were readily accessed and studied by experimental and computed Raman spectra. The ring-opening reaction of the Diazetidine was explored and resulted in the identification of a selective N–N bond cleavage with thiols as nucleophiles, which stereoselectively produced a new class of N-sulfenylimine derivatives with C-aminomethyl groups.
-
Synthesis of C‑Unsubstituted 1,2-Diazetidines and Their Ring-Opening Reactions via Selective N–N Bond Cleavage
2018Co-Authors: Hetti Handi Chaminda Lakmal, Bassem Ahmed, Christopher Fong, David J. Szalda, Keith Ramig, Andrzej Sygula, Charles Edwin Webster, Dongmao ZhangAbstract:C-Unsubstituted 1,2-Diazetidines, a rarely studied type of four-membered heterocyclic compounds, were synthesized through an operationally simple intermolecular vicinal disubstitution reaction. 1,2-Diazetidine derivatives bearing various N-arylsulfonyl groups were readily accessed and studied by experimental and computed Raman spectra. The ring-opening reaction of the Diazetidine was explored and resulted in the identification of a selective N–N bond cleavage with thiols as nucleophiles, which stereoselectively produced a new class of N-sulfenylimine derivatives with C-aminomethyl groups
Kenneth I. Hardcastle - One of the best experts on this subject based on the ideXlab platform.
-
Unexpected σ bond rupture during the reaction of N-methyl-1,2,4-triazoline-3,5-dione with acenaphthylene and indene.
The Journal of organic chemistry, 2014Co-Authors: Gary W. Breton, Joshua S. Hughes, Timothy J. Pitchko, Kenneth L. Martin, Kenneth I. HardcastleAbstract:The reaction of N-methyl-1,2,4-triazoline-3,5-dione (MeTAD) with acenaphthylene and indene leads not only to the formation of the expected [2 + 2] Diazetidine cycloadducts but also to unexpected 2:1 adducts of MeTAD with substrate. The structures of the products derived from acenaphthylene were confirmed by X-ray crystallography. A similar distribution of products was afforded from indene. The 2:1 adducts appear to derive from a diradical intermediate, the radical centers of which are strongly stabilized by the bridging urazoyl ring and benzylic delocalization. The triplet states of these diradical intermediates may be trapped via exposure to molecular oxygen to afford oxygen-containing adducts. Computational studies at the (U)B3LYP/6-31G* level provide additional support for the conclusions of our experimental work.
Duk Kyung Kim - One of the best experts on this subject based on the ideXlab platform.
-
The reaction of N-methyl-1,2,4-triazoline-3,5-dione with tetracyclopropylethylene. Formation of an unusual meso-ionic product and its rearrangement to the Diazetidine.
Journal of the American Chemical Society, 2004Co-Authors: Duk Kyung Kim, Kevin E. O'sheaAbstract:The reaction of N-methyl-1,2,4-triazoline-3,5-dione and tetracyclopropylethylene results in the quantitative formation of a meso-ionic compound. The formation of this unusual compound is likely the result of the unique conformational and steric properties of the cyclopropyl groups which inhibit the expected reaction pathways. The meso-ionic compound undergoes an unprecedented rearrangement to the Diazetidine upon warming to 55 °C.