The Experts below are selected from a list of 258 Experts worldwide ranked by ideXlab platform
Luiz F. Silva - One of the best experts on this subject based on the ideXlab platform.
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Adventures in Ring-Contraction reactions
Synlett, 2014Co-Authors: Luiz F. SilvaAbstract:Nearly two decades of work on Ring-Contraction reactions is discussed in this account. We have developed several reliable protocols for the rearrangement of a number of different substrates using thallium(III) salts and, more recently, hypervalent iodine(III) reagents. A variety of Ring systems, such as cyclopentanes, cis- and trans-hydrindanes, and indanes, can be obtained using these methods. Additionally, the stereoselective total syntheses of the sesquiterpenes (±)-, (–)- and (+)-mutisianthol and (+)-bakkenolide A, the indole alkaloid (±)- and (+)-trans-trikentrin A, and the potential drug (±)-indatraline have been achieved through a Ring-Contraction approach. 1 Introduction 2 Ring-Contraction Reactions Promoted by Thallium(III) 2.1 Thallium(III)-Mediated Ring Contraction of Cyclic Ketones 2.2 Thallium(III)-Mediated Ring Contraction of Cyclic Olefins 2.3 Thallium(III)-Mediated Ring Contraction of Homoallylic Alcohols 3 Ring-Contraction Reactions Promoted by Iodine(III) 4 Conclusion
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Stereoselective Synthesis of Drugs and Natural Products - Ring Contraction Reactions in the Total Synthesis of Biologically Active Natural Products
Stereoselective Synthesis of Drugs and Natural Products, 2013Co-Authors: Luiz F. SilvaAbstract:Strategic reactions in synthetic organic chemistry are those that increase the molecular complexity of the starting material. Particularly important are the transformations where new carbon–carbon bonds are formed. Although duRing a Ring Contraction the number of carbon–carbon bonds is conserved, the reorganization of the skeleton may occur with a high level of selectivity leading to a product not easily accessed by other methods. Even highly strained systems can be obtained using the Favorskii and Wolff rearrangements. Additionally, a Ring Contraction approach opens new applications for the chiral pool and for readily available starting materials. This chapter presents Ring Contraction reactions as an efficient tool in the stereoselective synthesis of biologically active natural products. The reactions discussed are Favorskii rearrangement, oxidative rearrangements, Wolff rearrangement, thermolysis of aryliodonium ylides, and rearrangements through cationic and radical intermediates. Keywords: Ring Contraction; total synthesis; rearrangement; CC bond formation; hypervalent iodine; stereoselective synthesis; reorganization of skeleton; Favorskii rearrangement; Wolff rearrangement; oxidative rearrangement; thermolysis; cationic intermediate; radical intermediate
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A Ring Contraction Strategy Toward a Diastereoselective Total Synthesis of (+)‐Bakkenolide A (VII).
ChemInform, 2010Co-Authors: Vânia M. T. Carneiro, Eloisa E. Ishikawa, Helena M C Ferraz, Tiago O. Vieira, Luiz F. SilvaAbstract:The key steps are a Ring Contraction of the octalone (I) and stereoselective formation of the keto ester (VI).
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hypervalent iodine mediated Ring Contraction reactions
Molecules, 2006Co-Authors: Luiz F. SilvaAbstract:Abstract : Hypervalent iodine reagents constitute a powerful tool in modern synthetic organic chemistry, promoting several important reactions. One such reaction is the Ring Contraction of cycloalkenes and cycloalkanones promoted by iodine(III) compounds, such as iodobenzene diacetate, iodosylbenzene, iodotoluene difluoride, and [hydroxy(tosyloxy)-iodo]benzene (Koser´s reagent). This review covers all the literature related to the Ring Contraction of cyclic ketones and olefins promoted by iodine(III) species. Keywords: Iodine(III), hypervalent iodine, Ring Contraction, oxidation, cycloalkenes, cycloalkanones. Introduction Ring Contraction reactions are an important method to increase molecular complexity in a single step, because, in several cases, the reorganization of the bonds occurs with a high level of selectivity, affording products not easily accessible by other approaches [1]. Ring Contraction reactions can be effected by acids, by bases, by oxidizers or photochemically [1]. Among the oxidizers, one of the most used is thallium trinitrate (TTN) [2, 3]. In the last years, hypervalent iodine reagents have become an essential tool in synthetic organic chemistry, due to the plethora of reactions that can be performed with them in excellent yield and selectivity. One such reaction is the oxidative rearrangement of cycloalkenes and cycloalkanones, which leads to a Ring Contraction. Although several reviews concerning hypervalent iodine chemistry have been published [4-15], none of them covered Ring Contraction reactions in a comprehensive manner. This review intends to cover the literature related to the Ring Contraction reaction of cyclic
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Hypervalent iodine-mediated Ring Contraction reactions.
Molecules (Basel Switzerland), 2006Co-Authors: Luiz F. SilvaAbstract:Hypervalent iodine reagents constitute a powerful tool in modern synthetic organic chemistry, promoting several important reactions. One such reaction is the Ring Contraction of cycloalkenes and cycloalkanones promoted by iodine(III) compounds, such as iodobenzene diacetate, iodosylbenzene, iodotoluene difluoride, and [hydroxy(tosyloxy)- iodo]benzene (Koser s reagent). This review covers all the literature related to the Ring Contraction of cyclic ketones and olefins promoted by iodine(III) species.
Angelo Frongia - One of the best experts on this subject based on the ideXlab platform.
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Tandem Wittig Reaction-Ring Contraction of Cyclobutanes: A Route to Functionalized Cyclopropanecarbaldehydes.
Organic letters, 2019Co-Authors: Federico Cuccu, Lorenzo Serusi, Alberto Luridiana, Francesco Secci, Pierluigi Caboni, David J. Aitken, Angelo FrongiaAbstract:An original tandem reaction consisting of a Wittig reaction–Ring Contraction process between α-hydroxycyclobutanone and phosphonium ylides has been developed. Highly functionalized cyclopropanecarb...
Perali Ramu Sridhar - One of the best experts on this subject based on the ideXlab platform.
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Ring Contraction vs Ring expansion reactions of spiro cyclopropanecarboxylated sugars
ChemInform, 2014Co-Authors: Bandi Ramakrishna, Perali Ramu SridharAbstract:NIS-Mediated Ring-opening of spirocyclopropane carboxylated sugars (I) produces α,β-unsaturated esters (I) easily undergoing DBU-mediated Ring-Contraction to yield ketofuranoses (III)/(IV).
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Ring‐Contraction vs Ring‐Expansion Reactions of Spiro‐Cyclopropanecarboxylated Sugars.
ChemInform, 2014Co-Authors: Bandi Ramakrishna, Perali Ramu SridharAbstract:NIS-Mediated Ring-opening of spirocyclopropane carboxylated sugars (I) produces α,β-unsaturated esters (I) easily undergoing DBU-mediated Ring-Contraction to yield ketofuranoses (III)/(IV).
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Ring Contraction vs Ring expansion reactions of spiro cyclopropanecarboxylated sugars
Organic Letters, 2013Co-Authors: Bandi Ramakrishna, Perali Ramu SridharAbstract:Electrophilic Ring opening of spiro-cyclopropanecarboxylated sugars followed by reaction with DBU revealed interesting Ring-Contraction and Ring-expansion reactions depending on the substrate and the kind of hydroxyl protective group present adjacent to the spiro center. A stereoselective method for accessing a new class of carbon chain extended keto-furanoses and C-glycosylated bicyclic compounds is reported.
Federico Cuccu - One of the best experts on this subject based on the ideXlab platform.
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Tandem Wittig Reaction-Ring Contraction of Cyclobutanes: A Route to Functionalized Cyclopropanecarbaldehydes.
Organic letters, 2019Co-Authors: Federico Cuccu, Lorenzo Serusi, Alberto Luridiana, Francesco Secci, Pierluigi Caboni, David J. Aitken, Angelo FrongiaAbstract:An original tandem reaction consisting of a Wittig reaction–Ring Contraction process between α-hydroxycyclobutanone and phosphonium ylides has been developed. Highly functionalized cyclopropanecarb...
E W Garbisch - One of the best experts on this subject based on the ideXlab platform.
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Ring Contraction via a favorskii type rearrangement cycloundecanone
Organic Syntheses, 2003Co-Authors: J Wohllebe, E W GarbischAbstract:Ring Contraction via a Favorskii-type rearrangement: cycloundecanone intermediate: methyl 1-cycloundecenecarboxylate product: cycloundecanone Keywords: elimination, miscellaneous; esterification, unsubstituted monobasic acids; halogenation, bromination; rearrangements; benzene; sodium methoxide, powdered; hydrazoic acid
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Organic Syntheses - Ring Contraction via a Favorskii‐Type Rearrangement: Cycloundecanone
Organic Syntheses, 2003Co-Authors: J Wohllebe, E W GarbischAbstract:Ring Contraction via a Favorskii-type rearrangement: cycloundecanone intermediate: methyl 1-cycloundecenecarboxylate product: cycloundecanone Keywords: elimination, miscellaneous; esterification, unsubstituted monobasic acids; halogenation, bromination; rearrangements; benzene; sodium methoxide, powdered; hydrazoic acid
