The Experts below are selected from a list of 17607 Experts worldwide ranked by ideXlab platform
Shu-li You - One of the best experts on this subject based on the ideXlab platform.
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asymmetric chlorination Ring Expansion for the synthesis of α quaternary cycloalkanones
ChemInform, 2014Co-Authors: Qin Yin, Shu-li YouAbstract:A highly enantioselective chlorination/Ring-Expansion of cyclobutanols and oxa-cyclobutanols is achieved using dichlorodimethylhydantoin in the presence of N-Boc-L-phenylglycine as simple catalyst.
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asymmetric chlorination Ring Expansion for the synthesis of α quaternary cycloalkanones
Organic Letters, 2014Co-Authors: Qin Yin, Shu-li YouAbstract:A highly enantioselective chlorination/Ring Expansion cascade for the construction of cycloalkanones with an all-carbon quaternary center was realized (up to 97% ee). Oxa-cyclobutanol substrates were employed for the first time in the Ring Expansion reactions, affording the functionalized dihydrofuranones in excellent enantioselectivity.
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n heterocyclic carbene catalyzed Ring Expansion of formylcyclopropanes synthesis of 3 4 dihydro α pyrone derivatives
Organic Letters, 2009Co-Authors: Lixin Dai, Shu-li YouAbstract:N-Heterocyclic carbene catalyzed Ring Expansion of readily accessible 2-acyl-1-formylcyclopropanes was developed. With 5 mol % of triazolium salt 5 and 30 mol % of DBU, Ring Expansion of various 2-acyl-1-formylcyclopropanes led to 3,4-dihydro-α-pyrones in good to excellent yields.
Dean F Toste - One of the best experts on this subject based on the ideXlab platform.
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dual visible light photoredox and gold catalyzed arylative Ring Expansion
ChemInform, 2014Co-Authors: Xingzhong Shu, Miao Zhang, Heinz Frei, Dean F TosteAbstract:A tandem Ring Expansion/oxidation arylation reaction of small sized Ring substituted alkenes and allenes are developed.
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dual visible light photoredox and gold catalyzed arylative Ring Expansion
Journal of the American Chemical Society, 2014Co-Authors: Xingzhong Shu, Miao Zhang, Heinz Frei, Dean F TosteAbstract:A combination of visible light photocatalysis and gold catalysis is applied to a Ring Expansion–oxidative arylation reaction. The reaction provides an entry into functionalized cyclic ketones from the coupling reaction of alkenyl and allenyl cycloalkanols with aryl diazonium salts. A mechanism involving generation of an electrophilic gold(III)–aryl intermediate is proposed on the basis of mechanistic studies, including time-resolved FT-IR spectroscopy.
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gold i catalyzed enantioselective Ring Expansion of allenylcyclopropanols
ChemInform, 2009Co-Authors: Florian Kleinbeck, Dean F TosteAbstract:The asymmetric gold(I)-catalyzed Ring Expansion of 1-allenylcyclopropanols is described. The method provides synthetically valuable cyclobutanones with a vinyl-substituted quaternary stereogenic center in high enantioselectivities and yields. The method shows a broad substrate scope, tolerating protected alcohols and amines, alkenes, unsaturated esters, and acetals. The reaction is easily adjustable to large-scale synthesis, leading to product formation without significant loss of selectivity or yield with only 0.5 mol% catalyst loading.
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gold i catalyzed Ring Expansion of cyclopropanols and cyclobutanols
ChemInform, 2005Co-Authors: Jordan P Markham, Steven T Staben, Dean F TosteAbstract:The rearrangement of 1-alkynyl cyclobutanols and cyclopropanols to alkylidene cycloalkanones catalyzed by cationic triarylphosphine gold(I) complexes is described. The reaction tolerates terminal alkynes as well as alkyl, aryl, and halo-substitution at the acetylenic position and stereoselectively provides a single olefin isomer. The gold(I)-catalyzed rearrangement is stereospecific with regard to substituents on the Ring, thus providing a practical method for the stereoselective synthesis of highly substituted cyclopentanones from cyclopropanols. The reaction stereoselectively provides a single olefin isomer and is stereospecific with regard to substituents on the Ring via sequential gold(I)-catalyzed Ring Expansion reactions.
Yingyeung Yeung - One of the best experts on this subject based on the ideXlab platform.
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diastereoselective synthesis of functionalized pyrrolidines through n bromosuccinimide induced aziridine Ring Expansion cascade of cinnamylaziridine
ChemInform, 2015Co-Authors: Jing Zhou, Yingyeung YeungAbstract:The bromonium ion-induced aziridine Ring Expansion cascade affords a mixture of functionalized pyrrolidines (III) and piperidines (IV), with the former being the major products.
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diastereoselective synthesis of functionalized pyrrolidines through n bromosuccinimide induced aziridine Ring Expansion cascade of cinnamylaziridine
Organic and Biomolecular Chemistry, 2014Co-Authors: Jing Zhou, Yingyeung YeungAbstract:An efficient aziridine Ring Expansion cascade of cinnamylaziridine has been developed. N-Bromosuccinimide was used as the promoter. The resulting functionalized pyrrolidines are the fundamental units of many useful molecules.
David W. Lupton - One of the best experts on this subject based on the ideXlab platform.
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Synthesis of Spirocyclic γ-Lactones by Cascade Beckwith–Dowd Ring Expansion/Cyclization
2016Co-Authors: Judith Hierold, David W. LuptonAbstract:A range of spirocyclic γ-lactones have been prepared exploiting a Beckwith–Dowd Ring Expansion cascade involving 1-, 3-, 4-, and 5-carbon Expansion of cyclopentanone and cyclohexanone followed by 5-exo-trig or 5-exo-dig cyclization. This radical cascade reaction can be achieved with various substrates to provide a broad range of γ-lactones spirofused to 6- to 10-membered cycloalkanones
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synthesis of spirocyclic γ lactones by cascade beckwith dowd Ring Expansion cyclization
Organic Letters, 2012Co-Authors: Judith Hierold, David W. LuptonAbstract:A range of spirocyclic γ-lactones have been prepared exploiting a Beckwith–Dowd Ring Expansion cascade involving 1-, 3-, 4-, and 5-carbon Expansion of cyclopentanone and cyclohexanone followed by 5-exo-trig or 5-exo-dig cyclization. This radical cascade reaction can be achieved with various substrates to provide a broad range of γ-lactones spirofused to 6- to 10-membered cycloalkanones.
William P. Unsworth - One of the best experts on this subject based on the ideXlab platform.
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Iterative Assembly of Macrocyclic Lactones using Successive Ring Expansion Reactions
Chemistry: A European Journal, 2018Co-Authors: Thomas C. Stephens, Aggie Lawer, Thomas French, William P. UnsworthAbstract:: Macrocyclic lactones can be prepared from lactams and hydroxyacid derivatives via an efficient 3- or 4-atom iterative Ring Expansion protocol. The products can also be expanded using amino acid-based linear fragments, meaning that macrocycles with precise sequences of hydroxy- and amino acids can be assembled in high yields by "growing" them from smaller Rings, using a simple procedure in which high dilution is not required. The method should significantly expedite the practical synthesis of diverse nitrogen containing macrolide frameworks.
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Ring Expansion reactions in the synthesis of macrocycles and medium sized Rings
Chemistry: A European Journal, 2017Co-Authors: James R Donald, William P. UnsworthAbstract:Functionalised macrocycles and medium-sized Rings have applications in a number of scientific fields, ranging from medicinal chemistry and supramolecular chemistry, to catalysis and nanotechnology. However, their value in these areas can be undermined by a simple, but important limitation: large Ring systems are very often difficult to make. Traditional end-to-end cyclisation reactions of long linear precursors are typically unpredictable and impractical processes, mainly due to unfavourable enthalpic and entropic factors. Most published methods to make large Rings focus on minimising the damage inflicted by performing the difficult cyclisation step; in contrast, Ring-Expansion reactions enable it to be avoided altogether. In this Review article, it is highlighted how “growing” Rings from existing cyclic systems via Ring Expansion can expedite the efficient, practical and scalable synthesis of macrocycles and medium-sized Rings.
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The Synthesis of Structurally Diverse Macrocycles by Successive Ring Expansion.
ChemInform, 2016Co-Authors: Christiana Kitsiou, Jordan J. Hindes, Phillip I'anson, Paula Jackson, Thomas C. Wilson, Eleanor K. Daly, Hannah R. Felstead, Peter Hearnshaw, William P. UnsworthAbstract:Structurally diverse macrocycles and medium-sized Rings (9-24 membered scaffolds, 22 examples) can be generated through a telescoped acylation/Ring-Expansion sequence, leading to the insertion of linear fragments into cyclic β-ketoesters without performing a discrete macrocyclization step. The key β-ketoester motif is regenerated in the Ring-expanded product, meaning that the same sequence of steps can then be repeated (in theory indefinitely) with other linear fragments, allowing macrocycles with precise substitution patterns to be "grown" from smaller Rings using the successive Ring-Expansion (SuRE) method.
