The Experts below are selected from a list of 309 Experts worldwide ranked by ideXlab platform
Ashok K. Basak - One of the best experts on this subject based on the ideXlab platform.
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K2CO3-Catalyzed Rapid Conversion of N-Sulfonylhydrazones to Sulfinates.
ACS omega, 2020Co-Authors: Harshita Singh Korawat, Ashok K. BasakAbstract:N-Sulfonylhydrazones derived from alkyl, aryl, and heteroaryl aldehydes and ketones undergo rapid conversion into the corresponding Sulfinates when heated with 10 mol % K2CO3 in N,N'-dimethylethylene urea (DMEU) at elevated temperature. The reaction conditions are amenable to several functional groups and suitable for gram-scale synthesis. Under these base-catalyzed conditions, N-tosylhydrazones derived from O-allylated and O-propargylated 2-hydroxyarylaldehydes do not undergo the well-established intramolecular [3 + 2]-cycloaddition reactions and generate corresponding Sulfinates in good yields. The base-catalyzed transformation proceeds via crucial rapid intermolecular protonation of the diazo intermediate 11 to generate diazonium ion 12, which upon nucleophilic displacement by the sulfonyl ion 10 provides the desired Sulfinate selectively.
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Wittig Ylide Mediated Decomposition of N-Sulfonylhydrazones to Sulfinates
Organic letters, 2018Co-Authors: Deepika Choudhary, Vineeta Khatri, Ashok K. BasakAbstract:N-Sulfonylhydrazones generate Sulfinates selectively when treated with a stabilized Wittig ylide in a polar aprotic solvent at elevated temperature. The transition metal and base free decomposition method is applicable to N-sulfonylhydrazones generated from a number of aromatic and heteroaromatic aldehydes and ketones. In the case of N-tosylhydrazones derived from O-allyl and O-propargyl salicylaldehydes, selective formation of Sulfinate occurs over intramolecular [3 + 2]-cycloaddition reaction.
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Wittig Ylide Mediated Decomposition of N‑Sulfonylhydrazones to Sulfinates
2018Co-Authors: Deepika Choudhary, Vineeta Khatri, Ashok K. BasakAbstract:N-Sulfonylhydrazones generate Sulfinates selectively when treated with a stabilized Wittig ylide in a polar aprotic solvent at elevated temperature. The transition metal and base free decomposition method is applicable to N-sulfonylhydrazones generated from a number of aromatic and heteroaromatic aldehydes and ketones. In the case of N-tosylhydrazones derived from O-allyl and O-propargyl salicylaldehydes, selective formation of Sulfinate occurs over intramolecular [3 + 2]-cycloaddition reaction
Deepika Choudhary - One of the best experts on this subject based on the ideXlab platform.
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Wittig Ylide Mediated Decomposition of N-Sulfonylhydrazones to Sulfinates
Organic letters, 2018Co-Authors: Deepika Choudhary, Vineeta Khatri, Ashok K. BasakAbstract:N-Sulfonylhydrazones generate Sulfinates selectively when treated with a stabilized Wittig ylide in a polar aprotic solvent at elevated temperature. The transition metal and base free decomposition method is applicable to N-sulfonylhydrazones generated from a number of aromatic and heteroaromatic aldehydes and ketones. In the case of N-tosylhydrazones derived from O-allyl and O-propargyl salicylaldehydes, selective formation of Sulfinate occurs over intramolecular [3 + 2]-cycloaddition reaction.
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Wittig Ylide Mediated Decomposition of N‑Sulfonylhydrazones to Sulfinates
2018Co-Authors: Deepika Choudhary, Vineeta Khatri, Ashok K. BasakAbstract:N-Sulfonylhydrazones generate Sulfinates selectively when treated with a stabilized Wittig ylide in a polar aprotic solvent at elevated temperature. The transition metal and base free decomposition method is applicable to N-sulfonylhydrazones generated from a number of aromatic and heteroaromatic aldehydes and ketones. In the case of N-tosylhydrazones derived from O-allyl and O-propargyl salicylaldehydes, selective formation of Sulfinate occurs over intramolecular [3 + 2]-cycloaddition reaction
Vineeta Khatri - One of the best experts on this subject based on the ideXlab platform.
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Wittig Ylide Mediated Decomposition of N-Sulfonylhydrazones to Sulfinates
Organic letters, 2018Co-Authors: Deepika Choudhary, Vineeta Khatri, Ashok K. BasakAbstract:N-Sulfonylhydrazones generate Sulfinates selectively when treated with a stabilized Wittig ylide in a polar aprotic solvent at elevated temperature. The transition metal and base free decomposition method is applicable to N-sulfonylhydrazones generated from a number of aromatic and heteroaromatic aldehydes and ketones. In the case of N-tosylhydrazones derived from O-allyl and O-propargyl salicylaldehydes, selective formation of Sulfinate occurs over intramolecular [3 + 2]-cycloaddition reaction.
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Wittig Ylide Mediated Decomposition of N‑Sulfonylhydrazones to Sulfinates
2018Co-Authors: Deepika Choudhary, Vineeta Khatri, Ashok K. BasakAbstract:N-Sulfonylhydrazones generate Sulfinates selectively when treated with a stabilized Wittig ylide in a polar aprotic solvent at elevated temperature. The transition metal and base free decomposition method is applicable to N-sulfonylhydrazones generated from a number of aromatic and heteroaromatic aldehydes and ketones. In the case of N-tosylhydrazones derived from O-allyl and O-propargyl salicylaldehydes, selective formation of Sulfinate occurs over intramolecular [3 + 2]-cycloaddition reaction
Michael C Willis - One of the best experts on this subject based on the ideXlab platform.
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Mechanistic Studies of the Palladium-Catalyzed Desulfinative Cross-Coupling of Aryl Bromides and (Hetero)Aryl Sulfinate Salts.
Journal of the American Chemical Society, 2020Co-Authors: Antoine De Gombert, Alasdair I. Mckay, Christopher John Davis, Katherine M Wheelhouse, Michael C WillisAbstract:Pyridine and related heterocyclic Sulfinates have recently emerged as effective nucleophilic coupling partners in palladium-catalyzed cross-coupling reactions with (hetero)aryl halides. These Sulfinate reagents are straightforward to prepare, stable to storage and coupling reaction conditions, and deliver efficient reactions, thus offering many advantages, compared to the corresponding boron-derived reagents. Despite the success of these reactions, there are only scant details of the reaction mechanism. In this study, we use structural and kinetic analysis to investigate the mechanism of these important coupling reactions in detail. We compare a pyridine-2-Sulfinate with a carbocyclic Sulfinate and establish different catalyst resting states, and turnover limiting steps, for the two classes of reagent. For the carbocyclic Sulfinate, the aryl bromide oxidative addition complex is the resting state intermediate, and transmetalation is turnover-limiting. In contrast, for the pyridine Sulfinate, a chelated Pd(II) Sulfinate complex formed post-transmetalation is the resting-state intermediate, and loss of SO2 from this complex is turnover-limiting. We also investigated the role of the basic additive potassium carbonate, the use of which is crucial for efficient reactions, and deduced a dual function in which carbonate is responsible for the removal of free sulfur dioxide from the reaction medium, and the potassium cation plays a role in accelerating transmetalation. In addition, we show that Sulfinate homocoupling is responsible for converting Pd(OAc)2 to a catalytically active Pd(0) complex. Together, these studies shed light on the challenges that must be overcome to deliver improved, lower temperature versions of these synthetically important processes.
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Copper-Catalyzed Synthesis of Activated Sulfonate Esters from Boronic Acids, DABSO, and Pentafluorophenol
Organic Letters, 2018Co-Authors: Vincent Vedovato, Eric P. A. Talbot, Michael C WillisAbstract:The synthesis of pentafluorophenyl (PFP) sulfonate esters based on the Pd-catalyzed sulfination of aryl and heteroaryl boronic acids is reported. The Sulfinate intermediates are converted in situ to the corresponding sulfonate esters using a copper-catalyzed oxidative process, providing a broad range of PFP esters in good yields.
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Copper-Catalyzed Synthesis of Activated Sulfonate Esters from Boronic Acids, DABSO, and Pentafluorophenol
2018Co-Authors: Vincent Vedovato, Eric P. A. Talbot, Michael C WillisAbstract:The synthesis of pentafluorophenyl (PFP) sulfonate esters based on the Pd-catalyzed sulfination of aryl and heteroaryl boronic acids is reported. The Sulfinate intermediates are converted in situ to the corresponding sulfonate esters using a copper-catalyzed oxidative process, providing a broad range of PFP esters in good yields
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Heterocyclic Allylsulfones as Latent Heteroaryl Nucleophiles in Palladium-Catalyzed Cross-Coupling Reactions
2018Co-Authors: Tim Markovic, Philip R. D. Murray, Benjamin N. Rocke, Andre Shavnya, David C. Blakemore, Michael C WillisAbstract:Heterocyclic Sulfinates are effective reagents in palladium-catalyzed coupling reactions with aryl and heteroaryl halides, often providing high yields of the targeted biaryl. However, the preparation and purification of complex heterocylic Sulfinates can be problematic. In addition, Sulfinate functionality is not tolerant of the majority of synthetic transformations, making these reagents unsuitable for multistep elaboration. Herein, we show that heterocyclic allylsulfones can function as latent Sulfinate reagents and, when treated with a Pd(0) catalyst and an aryl halide, undergo deallylation, followed by efficient desulfinylative cross-coupling. A broad range of allyl heteroarylsulfones are conveniently prepared, using several complementary routes, and are shown to be effective coupling partners with a variety of aryl and heteroaryl halides. We demonstrate that the allylsulfone functional group can tolerate a range of standard synthetic transformations, including orthogonal C- and N-coupling reactions, allowing multistep elaboration. The allylsulfones are successfully coupled with a variety of medicinally relevant substrates, demonstrating their applicability in demanding cross-coupling transformations. In addition, pharmaceutical agents crizotinib and etoricoxib were prepared using allyl heteroaryl sulfone coupling partners, further demonstrating the utility of these new reagents
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palladium ii catalyzed synthesis of Sulfinates from boronic acids and dabso a redox neutral phosphine free transformation
Angewandte Chemie, 2016Co-Authors: Alex S Deeming, Claire Janet Russell, Michael C WillisAbstract:A redox-neutral palladium(II)-catalyzed conversion of aryl, heteroaryl, and alkenyl boronic acids into Sulfinate intermediates, and onwards to sulfones and sulfonamides, has been realized. A simple Pd(OAc)2 catalyst, in combination with the sulfur dioxide surrogate 1,4-diazabicyclo[2.2.2]octane bis(sulfur dioxide) (DABSO), is sufficient to achieve rapid and high-yielding conversion of the boronic acids into the corresponding Sulfinates. Addition of C- or N-based electrophiles then allows conversion into sulfones and sulfonamides, respectively, in a one-pot, two-step process.
Phil S Baran - One of the best experts on this subject based on the ideXlab platform.
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Preparation and purification of zinc Sulfinate reagents for drug discovery
Nature Protocols, 2013Co-Authors: Fionn O'hara, Ryan D Baxter, Alexander G O'brien, Michael R Collins, Janice A Dixon, Yuta Fujiwara, Yoshihiro Ishihara, Phil S BaranAbstract:The present protocol details the synthesis of zinc bis(alkaneSulfinate)s that can be used as general reagents for the formation of radical species. The zinc Sulfinates described herein are generated from the corresponding sulfonyl chlorides by treatment with zinc dust. The products may be used crude, or a simple purification procedure may be performed to minimize incorporation of water and zinc chloride. Although the synthesis of the zinc Sulfinate salts can generally be completed within 3 h, workup can take up to 24 h and purification can take up to 3 h. Following the steps in this protocol would enable the user to generate a small toolkit of zinc Sulfinate reagents over the course of 1 week.
