The Experts below are selected from a list of 426 Experts worldwide ranked by ideXlab platform
Rai-shung Liu - One of the best experts on this subject based on the ideXlab platform.
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Ground-state dioxygen undergoes metal-free [3 + 2]-annulations with allenes and nitrosoarenes under ambient conditions.
Chemical science, 2017Co-Authors: Jinxian Liu, Manisha Skaria, Pankaj Sharma, Yun-wei Chiang, Rai-shung LiuAbstract:The cycloadditions of molecular dioxygen with neutral π-bond motifs rely heavily on singlet-state 1O2, whereas ground state 3O2 is chemically inactive. Here we report novel [3 + 2]-annulations among ground-state 3O2 (1 bar), allenes, and nitrosoarenes at low temperatures, efficiently yielding dioxygen-containing Oxacycles. With less hindered 1-arylallene derivatives, these dioxygen species undergo skeletal rearrangement to 3-hydroxy-1-ketonyl-2-imine oxides. These cycloadditions represent valuable one-pot O,N,O-trifunctionalizations of allenes. Our EPR experiments confirm the presence of 1,4-diradical intermediates from an allene/nitrosoarene mixture, which manifest the hidden diradical properties of nitrosoarenes.
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A Sequential Route to Cyclopentenes from 1,6‐Enynes and Diazo Ketones through Gold and Rhodium Catalysis
Advanced Synthesis & Catalysis, 2017Co-Authors: Balaji S. Kale, Hsin-fu Lee, Rai-shung LiuAbstract:This work reports the construction of cyclopentene cores from 1,6-enynes and aryl diazo ketones through two new reaction sequences involving initial gold-catalyzed cyclization of 1,6-enynes with diazo species, followed by rhodium-catalyzed skeletal rearrangement of the resulting 3-cyclopropyl-2-en-1-ones. In most instances the rhodium-catalyzed reactions afforded cyclopentene derivatives whereas several n-alkyl- or ortho-substituted phenyl ketones delivered seven-membered Oxacycles. A plausible mechanism provides rationales for these two distinct products.
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Oxy Effects on the Platinum‐Catalyzed Carbo‐ and Oxacyclizations of 2‐Oxiranyl‐1‐(1‐oxyalk‐2‐ynyl)benzenes
Advanced Synthesis & Catalysis, 2012Co-Authors: Rupsha Chaudhuri, Samir Kundlik Pawar, Kamalkishore Pati, Rai-shung LiuAbstract:We report new platinum-catalyzed proto- cols for the synthesis of carbocycles and Oxacycles from 2-oxiranyl-1-(1-oxyalk-2-ynyl)benzenes. For 1,2,2-trisubstituted epoxides bearing an acyloxy group, their platinum-catalyzed cyclizations proceed through an initial 1,3-acyloxy shift, followed by an intramolecular attack of an allenyl acetate at the car- bonyl group, ultimately giving 2-naphthyl ketones through a selective 1,2-alkyl shift. 1,1-Disubstituted epoxides bearing a siloxy group un- dergo an oxacyclization to give bicyclic ketals with high diastereoselectivity.
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Gold-Catalyzed Stereoselective Synthesis of 9-Oxabicyclo[3.3.1]nona-4,7-dienes from Diverse 1-Oxo-4-oxy-5-ynes: A Viable Formal [4 + 2] Cycloaddition on an s-trans-Heterodiene Framework
Journal of the American Chemical Society, 2010Co-Authors: Tsemin Teng, Deepak B Huple, Arindam Das, Rai-shung LiuAbstract:We report a highly stereoselective Au-catalyzed synthesis of 9-oxabicyclo[3.3.1]nona-4,7-dienes from diverse 1-oxo-4-oxy-5-ynes. Formation of these highly strained anti-Bredt Oxacycles implies the workability of an unprecedented 1,4-dipole of s-trans-methylene(vinyl)oxonium. This work reveals the feasibility of a formal [4 + 2] cycloaddition on an s-trans-heterodiene framework.
Julio D Martin - One of the best experts on this subject based on the ideXlab platform.
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Simple Designs for the Construction of Complex Trans-Fused Polyether Toxin Frameworks. A Convergent Strategy Based on Hydroxy Ketone Cyclization of C-Linked Oxacycles.
The Journal of organic chemistry, 1996Co-Authors: Eleuterio Álvarez, Ricardo Pérez, Milagros Rico, Rosa M. Rodríguez, Julio D MartinAbstract:A single, unified convergent strategy for the stereocontrolled synthesis of trans-fused polyethers was developed. It was demonstrated that the epimerization and reductive intramolecular coupling of hydroxy ketones in reactions with silane−Lewis acids (SI−LA) to generate ethers in C-linked Oxacycles is affected by its conformational preference in a predictable manner. The obtained results make evident that the influence of hydrogen bonding between a hemiketal hydroxyl and a 1,3-diaxial C−O bond is regular and predictable and that convergent synthesis of trans-fused polyethers may confidently be conducted on driving ring closure to oxane rings under thermodynamic conditions
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synthetic studies towards ciguatoxin via acetal γ oxovinyl stannane condensation a convergent approach
Tetrahedron Letters, 1996Co-Authors: Joseluis Ravelo, Alicia Regueiro, Elsa Rodriguez, Jose De Vera, Julio D MartinAbstract:Abstract A two-directional approach converting acetals to O-linked Oxacycles, by way of intramolecular allyl tin-acetal condensation, is described.
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Synthetic studies towards ciguatoxin via acetal/γ-oxovinyl stannane condensation: A convergent approach
Tetrahedron Letters, 1996Co-Authors: Joseluis Ravelo, Alicia Regueiro, Elsa Rodriguez, Jose De Vera, Julio D MartinAbstract:Abstract A two-directional approach converting acetals to O-linked Oxacycles, by way of intramolecular allyl tin-acetal condensation, is described.
Benito Alcaide - One of the best experts on this subject based on the ideXlab platform.
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Metal-Mediated Synthesis of Nonaromatic Oxacycles From Allenols
Advances in Transition-Metal Mediated Heterocyclic Synthesis, 2018Co-Authors: Benito Alcaide, Pedro Almendros, Teresa Martínez Del CampoAbstract:Abstract The allene moiety represents an excellent building block for metal-mediated cyclization reactions, affording heterocyclic skeletons in a single step. The aim of this chapter is to present regiocontrolled metal-mediated preparations of nonaromatic Oxacycles starting from allenols through intramolecular reactions. This chapter summarizes recent applications toward the synthesis of Oxacycles taking into account the nature of the metal catalyst. This manuscript provides a personal overview on some of the topics that, from our viewpoint, are the most relevant.
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Gold‐Photoredox‐Cocatalyzed Tandem Oxycyclization/Coupling Sequence of Allenols and Diazonium Salts with Visible Light Mediation
Advanced Synthesis & Catalysis, 2017Co-Authors: Benito Alcaide, Pedro Almendros, Borja Aparicio, Carlos Lázaro-milla, Amparo Luna, Olalla Nieto FazaAbstract:The room temperature radical cycloetherification/arylation cascade of allenols and diazonium salts has been accomplished via a combination of gold and photoredox catalysis to provide 2,3,4-trisubstituted-2,5-dihydrofurans. The functionalized Oxacycle formation sequence is chemo- and regioselective for the cycloetherification and for the position that bears the aryl moiety after the cross-coupling. Mechanistic investigations revealed that this transformation proceeds through an initial oxidation of gold(I) to a phenyl gold(III) complex, which, upon coordination to the allene, catalyzes its cyclization and leads to the coupling product after a reductive elimination regenerating Au(I).
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synthesis of fused β lactams through selective gold catalyzed oxycyclization of dioxolane tethered enynes
ChemInform, 2014Co-Authors: Benito Alcaide, Pedro Almendros, Teresa Martínez Del Campo, Rosario M TorresAbstract:The gold-catalyzed preparation of 2-azetidinone-fused Oxacycles is accomplished from β-lactam-linked enynes through heterocyclization reaction taking advantage of the acetonide pendant group.
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Synthesis of Fused‐β‐Lactams Through Selective Gold‐Catalyzed Oxycyclization of Dioxolane‐Tethered Enynes.
ChemInform, 2014Co-Authors: Benito Alcaide, Pedro Almendros, Teresa Martínez Del Campo, M. Rosario TorresAbstract:The gold-catalyzed preparation of 2-azetidinone-fused Oxacycles is accomplished from β-lactam-linked enynes through heterocyclization reaction taking advantage of the acetonide pendant group.
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synthesis of fused β lactams through selective gold catalyzed oxycyclization of dioxolane tethered enynes
Journal of Organic Chemistry, 2013Co-Authors: Benito Alcaide, Pedro Almendros, Teresa Martínez Del Campo, Rosario M TorresAbstract:The gold-catalyzed preparation of 2-azetidinone-fused Oxacycles was accomplished from β-lactam-linked enynes through heterocyclization reaction taking advantage of the acetonide pendant group. While the synthesis of fused tetrahydrofuran-β-lactams from 1,3-enynes could be considered as an unusual metal-catalyzed cyclization of enynols, α-alkoxy dioxolane-tethered 1,3-enynes exclusively undergo bis-oxycyclization to afford tricyclic bridged acetals.
Deepak B Huple - One of the best experts on this subject based on the ideXlab platform.
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Gold-Catalyzed Stereoselective Synthesis of 9-Oxabicyclo[3.3.1]nona-4,7-dienes from Diverse 1-Oxo-4-oxy-5-ynes: A Viable Formal [4 + 2] Cycloaddition on an s-trans-Heterodiene Framework
Journal of the American Chemical Society, 2010Co-Authors: Tsemin Teng, Deepak B Huple, Arindam Das, Rai-shung LiuAbstract:We report a highly stereoselective Au-catalyzed synthesis of 9-oxabicyclo[3.3.1]nona-4,7-dienes from diverse 1-oxo-4-oxy-5-ynes. Formation of these highly strained anti-Bredt Oxacycles implies the workability of an unprecedented 1,4-dipole of s-trans-methylene(vinyl)oxonium. This work reveals the feasibility of a formal [4 + 2] cycloaddition on an s-trans-heterodiene framework.
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gold catalyzed stereoselective synthesis of 9 oxabicyclo 3 3 1 nona 4 7 dienes from diverse 1 oxo 4 oxy 5 ynes a viable formal 4 2 cycloaddition on an s trans heterodiene framework
Journal of the American Chemical Society, 2010Co-Authors: Tsemin Teng, Deepak B HupleAbstract:We report a highly stereoselective Au-catalyzed synthesis of 9-oxabicyclo[3.3.1]nona-4,7-dienes from diverse 1-oxo-4-oxy-5-ynes. Formation of these highly strained anti-Bredt Oxacycles implies the workability of an unprecedented 1,4-dipole of s-trans-methylene(vinyl)oxonium. This work reveals the feasibility of a formal [4 + 2] cycloaddition on an s-trans-heterodiene framework.
Tsemin Teng - One of the best experts on this subject based on the ideXlab platform.
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Gold-Catalyzed Stereoselective Synthesis of 9-Oxabicyclo[3.3.1]nona-4,7-dienes from Diverse 1-Oxo-4-oxy-5-ynes: A Viable Formal [4 + 2] Cycloaddition on an s-trans-Heterodiene Framework
Journal of the American Chemical Society, 2010Co-Authors: Tsemin Teng, Deepak B Huple, Arindam Das, Rai-shung LiuAbstract:We report a highly stereoselective Au-catalyzed synthesis of 9-oxabicyclo[3.3.1]nona-4,7-dienes from diverse 1-oxo-4-oxy-5-ynes. Formation of these highly strained anti-Bredt Oxacycles implies the workability of an unprecedented 1,4-dipole of s-trans-methylene(vinyl)oxonium. This work reveals the feasibility of a formal [4 + 2] cycloaddition on an s-trans-heterodiene framework.
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gold catalyzed stereoselective synthesis of 9 oxabicyclo 3 3 1 nona 4 7 dienes from diverse 1 oxo 4 oxy 5 ynes a viable formal 4 2 cycloaddition on an s trans heterodiene framework
Journal of the American Chemical Society, 2010Co-Authors: Tsemin Teng, Deepak B HupleAbstract:We report a highly stereoselective Au-catalyzed synthesis of 9-oxabicyclo[3.3.1]nona-4,7-dienes from diverse 1-oxo-4-oxy-5-ynes. Formation of these highly strained anti-Bredt Oxacycles implies the workability of an unprecedented 1,4-dipole of s-trans-methylene(vinyl)oxonium. This work reveals the feasibility of a formal [4 + 2] cycloaddition on an s-trans-heterodiene framework.
