Publications by authors named "Sarah E Wengryniuk"
J Org Chem
September 2024
Article Synopsis
- Aminated nitrogen heterocycles are important in various chemical fields, especially in drug discovery, but traditional methods for adding nitrogen to them often require complex pre-steps and are mainly restricted to one position (C2).
- The new method introduced allows for direct C-H amination at both C2 and C4 positions of fused azaarenes using a specific I(III) reagent, eliminating the need for preoxidation and enabling higher accessibility for C4 products.
- This technique not only simplifies the process and improves yields, but also offers insights into the mechanism, showcasing a unique way of activating the reagent and explaining the formation of the different amination products.
Article Synopsis
- - The study presents a metal-free method for C-H amination of arenes using a reagent that transfers a heterocyclic group, specifically from an I(III) -HVI compound.
- - N-Heterocycles are used as masked amine nucleophiles, resulting in stable -arylpyridinium salts that resist further oxidation.
- - The reaction occurs under mild conditions and involves an arene radical cation as an intermediate, with the ability to transform the pyridinium salts into various aryl amine structures.
Article Synopsis
- Alkylpyridinium salts are useful in cross-coupling reactions but are expensive and inefficient to produce, particularly the common 2,4,6-triphenylpyridinium salt.
- There’s an increasing demand for better and more cost-effective ways to create these salts.
- This study introduces a new method for synthesizing benzylic 2,4,6-collidinium salts using electrooxidative C-H functionalization, offering a better alternative to the usual methods that require more complex starting materials.
J Org Chem
September 2021
Article Synopsis
- Hypervalent iodine (HVI) compounds can effectively oxidize electron-rich phenols to -quinones, and a new class of iodine(V) reagents called Bi()-HVIs enables the oxidation of electron-poor phenols, which was previously unexplored.
- Researchers used density functional theory (DFT) to study the mechanisms behind the effectiveness of Bi()-HVIs compared to traditional hypervalent iodine species like IBX.
- The study revealed that the reactivity relies on the ligands attached to the iodine(V); weakly coordinating ligands allow for a favorable redox process, while strongly coordinating ones hinder necessary reaction steps.
Article Synopsis
- - Quinones are important molecules used in various fields like biology and materials science, but synthesizing them, especially from phenols, can be difficult due to specific oxidation requirements and the instability of the products.
- - The text discusses the role of I(V) hypervalent iodine reagents as effective oxidants for producing regioselective quinones and quinols from phenols.
- - It highlights recent advancements, including a new method using nitrogen-ligated I(V) reagents for oxidizing certain phenols, and notes ongoing developments in creating chiral reagents for asymmetric synthesis.
Article Synopsis
- - Pyridinium and related -alkyl(heteroaryl)onium salts are important in organic chemistry for creating various compounds, but their synthesis methods have not advanced much recently.
- - This study introduces a new method using bis(cationic nitrogen-ligated I(iii) hypervalent iodine reagents (HVIs) to efficiently produce a wide range of these onium salts from alkenoic acids, marking a novel approach by directly utilizing olefins.
- - The reactions yield high results in mild conditions, allowing for diverse aromatic heterocycles to be incorporated, and demonstrate significant potential for creating different nitrogen heterocycles through subsequent derivatizations.
Article Synopsis
- Hypervalent iodine(V) reagents are effective organic oxidants, but traditional compounds like Dess-Martin periodinane and IBX face challenges with solubility and stability.
- The study introduces a new class of I(V) reagents called Bi()-HVIs, which use bidentate nitrogen ligands to improve these issues.
- Bi()-HVIs offer better safety, enhanced solubility, and comparable or superior oxidative reactivity, making them a promising option for further I(V) reagent and reaction development.
J Am Chem Soc
January 2020
Article Synopsis
- α-Arylation of α,β-unsaturated ketones is an important synthetic process, typically done using costly cross-coupling methods that need pre-prepared substrates.*
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- This study introduces a more efficient method for direct C-H arylation of enones, using hypervalent iodine compounds without the need for metals.*
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- The reaction utilizes a unique mechanism involving β-pyridinium silyl enol ethers and allows a variety of aryl group substitutions while retaining useful iodine groups.*
Angew Chem Int Ed Engl
November 2019
Article Synopsis
- - The synthesis of electron-deficient ortho-quinones has been difficult, but a new method using direct oxidation of phenols has been developed.
- - This method employs a novel bidentate nitrogen-ligated iodine(V) reagent, called Bi(N)-HVIs, which shows excellent selectivity for producing ortho isomers.
- - The process allows for easy functionalization of the resulting ortho-quinones, enabling one-pot synthesis of catechols and the introduction of various nucleophiles, highlighting the potential of Bi(N)-HVIs in synthetic chemistry.
Article Synopsis
- The functionalization of alcohols in complex polyols is challenging, with progress made in selective oxygen derivatization but limited advancements in chemoselective oxidation to carbonyls.
- This research introduces a new reagent, nitrogen-ligated (bis)cationic λ-iodanes, which shows high selectivity for oxidizing equatorial alcohols while avoiding axial alcohols in cyclic systems.
- The methodology is mild and the reagent can be easily synthesized or generated in situ, making it a useful tool for chemists working on selective oxidation in various alcohol structures.
Article Synopsis
- The α-alkylation of ketones is a key reaction in chemistry, especially for creating compounds that have significant natural and medicinal applications.
- The authors previously introduced a new enantioselective method using N-amino cyclic carbamate (ACC) auxiliaries, which has shown to be more effective than traditional methods.
- This text presents a comprehensive discussion of their studies and findings related to the ACC ketone α-alkylation technique, emphasizing its high enantioselectivity and yield.
European J Org Chem
March 2018
Article Synopsis
- * The method produces HFIP-acetals that can easily be modified with various nucleophiles, offering flexibility for further chemical reactions.
- * The approach is shown to be beneficial in modifying natural products, aiding diversity-oriented synthesis, while early experiments suggest the shape of the alcohol significantly influences the reaction outcomes, which could help predict results in complex molecule creation.
Article Synopsis
- High valent metal complexes have become crucial in modern catalysis over the last two decades, particularly for creating carbon-heteroatom bonds.
- The success of this chemistry relies on finding effective oxidants that can support these high oxidation state complexes, providing necessary heteroatom ligands for reactions.
- Hypervalent iodine reagents are highlighted as key tools, offering versatile reactivity under mild conditions while being eco-friendly, non-toxic, and cost-effective compared to traditional oxidants.
Article Synopsis
- Terpenes pallambins C and D were synthesized in 11 steps using furfuryl alcohol, a cost-effective starting material.
- The synthesis employs a redox-economic strategy that avoids the need for protecting-group manipulations, utilizing a sequential cyclization method to create four-ring structures.
- This work introduced new techniques, including two classical reactions (Robinson annulation and Mukaiyama aldol) and a novel method for difunctionalizing enol ethers, expanding the potential applications of this transformation.
Article Synopsis
- - A new, easy method has been created for making medium-sized cyclic ethers through a unique process that rearranges benzylic tertiary alcohols.
- - This reaction allows for the formation of cyclic acetals that have different substituents on both C2 and the aromatic ring.
- - This approach uses special poly(cationic) hypervalent iodine reagents and marks the first time such compounds have been synthesized in this way.
Article Synopsis
- A novel technique for selectively brominating C2 positions on fused azine N-oxides is introduced, using tosic anhydride to activate the reaction and tetra-n-butylammonium bromide as the bromide source.
- The method yields C2-brominated compounds at moderate to excellent levels, with strong regioselectivity in most cases.
- The approach could potentially be adapted for C2-chlorination using Ts(2)O/TBACl, and it can be integrated into a one-pot process that combines oxidation and bromination with specific oxidants.
Article Synopsis
- The study presents the first asymmetric total synthesis of apratoxin D, a powerful compound that inhibits human lung cancer cell growth with an IC(50) value of 2.6 nM.
- To achieve this, the researchers used asymmetric N-amino cyclic carbamate α,α-bisalkylation to effectively create the C-37 methyl group with high selectivity.
- Additionally, they implemented key asymmetric reactions, including Evans syn-aldol and Paterson anti-aldol transformations, both demonstrating excellent stereoselectivity.
Article Synopsis
- - This text introduces a new method for the asymmetric α,α-bisalkylation of ketones that have protons at both the α and α' positions, achieving high regio- and stereoselectivity.
- - The method relies on complex-induced syn-deprotonation (CIS-D), which alters the typical behavior of lithium diisopropylamide (LDA) by selectively removing protons in a way that contrasts with conventional expectations.
- - The effectiveness of this approach is highlighted through a formal synthesis of the enantiomers (R)- and (S)-stigmolone, demonstrating that either ketone can be accessed using only one enantiomer of the auxiliary compound.
Article Synopsis
- * It finds that the rigid structure of the camphor-derived ACC influences the energy differences between conformations of the azaenolate intermediate, which in turn affects how an electrophile adds to it.
- * While previous reports indicated certain stereoselectivity values for the reaction, computational predictions suggest even higher selectivity; however, the removal of the ACC auxiliary can negatively impact the stereoselectivity of the alkylation process.
