scholarly journals Tuning the reactivity of alkoxyl radicals from 1,5-hydrogen atom transfer to 1,2-silyl transfer

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Zhaoliang Yang ◽  
Yunhong Niu ◽  
Xiaoqian He ◽  
Suo Chen ◽  
Shanshan Liu ◽  
...  
Keyword(s):  
Hydrogen Atom ◽  
Functional Groups ◽  
Reactive Intermediates ◽  
Hydrogen Atom Transfer ◽  
Hydroxyl Groups ◽  
Atom Transfer ◽  
Silyl Group ◽  
Carbon Radicals ◽  
Synthetic Intermediates ◽  
Direct Generation

AbstractControlling the reactivity of reactive intermediates is essential to achieve selective transformations. Due to the facile 1,5-hydrogen atom transfer (HAT), alkoxyl radicals have been proven to be important synthetic intermediates for the δ-functionalization of alcohols. Herein, we disclose a strategy to inhibit 1,5-HAT by introducing a silyl group into the α-position of alkoxyl radicals. The efficient radical 1,2-silyl transfer (SiT) allows us to make various α-functionalized products from alcohol substrates. Compared with the direct generation of α-carbon radicals from oxidation of α-C-H bond of alcohols, the 1,2-SiT strategy distinguishes itself by the generation of alkoxyl radicals, the tolerance of many functional groups, such as intramolecular hydroxyl groups and C-H bonds next to oxygen atoms, and the use of silyl alcohols as limiting reagents.

Regioselective C(sp3)–H alkylation of a fructopyranose derivative by 1,6-HAT

2021 ◽  
Vol 19 (14) ◽  
pp. 3124-3127
Author(s):  
Yanru Li ◽  
Shoto Miyamoto ◽  
Takeru Torigoe ◽  
Yoichiro Kuninobu
Keyword(s):  
Hydrogen Atom ◽  
Functional Groups ◽  
Hydrogen Atom Transfer ◽  
Atom Transfer

We developed regioselective C(sp3)–H alkylation of a fructopyranose derivative, which enables the introduction of several functional groups, by 1,6-hydrogen atom transfer.

1.13 Intramolecular Hydrogen-Atom Transfer

2021 ◽  
Author(s):  
S. Treacy ◽  
X. Zhang ◽  
T. Rovis
Keyword(s):  
Hydrogen Atom ◽  
Functional Groups ◽  
Open Shell ◽  
Hydrogen Atom Transfer ◽  
Atom Transfer ◽  
Stable Carbon ◽  
Radical Reactivity ◽  
Recent Advances ◽  
Synthetic Chemist ◽  
Intramolecular Hydrogen

AbstractRecent advances in intramolecular hydrogen-atom transfer (HAT) have demonstrated significant utility in C—H functionalization through highly reactive open-shell intermediates. The intramolecular transposition of radical reactivity from select functional groups to generate more stable carbon-centered radicals often proceeds with high regioselectivity, providing novel bond disconnections at otherwise inert and largely indistinguishable positions. This chapter explores the functional groups capable of intramolecular HAT to generate remote radicals and the transformations currently available to the synthetic chemist.

scholarly journals Catalytic Radical-Polar Crossover Ritter Reaction

2021 ◽  
Author(s):  
Eric Touney ◽  
Riley Cooper ◽  
Sarah Bredenkamp ◽  
David George ◽  
Sergey Pronin
Keyword(s):  
Hydrogen Atom ◽  
Hydrogen Evolution ◽  
Functional Groups ◽  
Hydrogen Atom Transfer ◽  
Catalyst Design ◽  
Ritter Reaction ◽  
Organic Reactions ◽  
Atom Transfer ◽  
Substitution Pattern ◽  
Diverse Range

A catalytic radical-polar crossover Ritter reaction is described. The transformation proceeds under acid-free conditions and tolerates a variety of functional groups. The catalyst design overcomes limitations in the substitution pattern of starting materials and enables hydroamidation of a diverse range of alkenes. Formation of hydrogen contributes to the background consumption of reductant and oxidant and competes with the desired pathway, pointing to a mechanistic link between hydrogen atom transfer-initiated organic reactions and hydrogen evolution catalysis.

scholarly journals Modifying Positional Selectivity in C–H Functionalization Reactions with Nitrogen-Centered Radicals: Generalizable Approaches to 1,6-Hydrogen-Atom Transfer Processes

Synlett ◽  
2019 ◽  
Vol 31 (02) ◽  
pp. 102-116 ◽  
Author(s):  
Melanie A. Short ◽  
J. Miles Blackburn ◽  
Jennifer L. Roizen
Keyword(s):  
Hydrogen Atom ◽  
Functional Groups ◽  
Reactive Species ◽  
Hydrogen Atom Transfer ◽  
Atom Transfer ◽  
Structural Constraints ◽  
Reaction Intermediates ◽  
Transfer Processes ◽  
Selective Functionalization ◽  
Site Selectivity

Nitrogen-centered radicals are powerful reaction intermediates owing in part to their ability to guide position-selective C(sp3)–H functionalization reactions. Typically, these reactive species dictate the site of functionalization by preferentially engaging in 1,5-hydrogen-atom transfer (1,5-HAT) processes. Broadly relevant approaches to alter the site-selectivity of HAT pathways would be valuable because they could be paired with a variety of tactics to install diverse functional groups. Yet, until recently, there have been no generalizable strategies to modify the position-selectivity observed in these HAT processes. This Synpacts article reviews transformations in which nitrogen-centered radicals preferentially react through 1,6-HAT pathways. Specific attention will be focused on strategies that employ alcohol- and amine-anchored sulfamate esters and sulfamides as templates to achieve otherwise rare γ-selective functionalization reactions.1 Introduction2 Transformations that Rely on Structural Constraints or Weakened C–H Bonds to Favor 1,6-HAT Processes3 Sulfamate Esters Engage Selective 1,6-HAT Processes4 Expansion to 1,6-HAT Processes with Masked Amine Substrates5 Conclusions and Outlook

scholarly journals Catalytic Radical-Polar Crossover Ritter Reaction

2021 ◽  
Author(s):  
Eric Touney ◽  
Riley Cooper ◽  
Sarah Bredenkamp ◽  
David George ◽  
Sergey Pronin
Keyword(s):  
Hydrogen Atom ◽  
Hydrogen Evolution ◽  
Functional Groups ◽  
Hydrogen Atom Transfer ◽  
Catalyst Design ◽  
Ritter Reaction ◽  
Organic Reactions ◽  
Atom Transfer ◽  
Substitution Pattern ◽  
Diverse Range

A catalytic radical-polar crossover Ritter reaction is described. The transformation proceeds under acid-free conditions and tolerates a variety of functional groups. The catalyst design overcomes limitations in the substitution pattern of starting materials and enables hydroamidation of a diverse range of alkenes. Formation of hydrogen contributes to the background consumption of reductant and oxidant and competes with the desired pathway, pointing to a mechanistic link between hydrogen atom transfer-initiated organic reactions and hydrogen evolution catalysis.

Direct Cyclization of Alkenyl Thioester via Transition Metal‐hydrogen Atom Transfer/radical‐polar Crossover Mechanism

2019 ◽  
Author(s):  
Shiori Date ◽  
Kensei Hamasaki ◽  
Karen Sunagawa ◽  
Hiroki Koyama ◽  
Chikayoshi Sebe ◽  
...  
Keyword(s):  
Natural Products ◽  
Hydrogen Atom ◽  
Transition Metal ◽  
Hydrogen Atom Transfer ◽  
Synthetic Method ◽  
Atom Transfer ◽  
Reaction Conditions ◽  
Hydride Hydrogen ◽  
Sulfur Heterocycles ◽  
One Step

<div>We report here a catalytic, Markovnikov selective, and scalable synthetic method for the synthesis of saturated sulfur heterocycles, which are found in the structures of pharmaceuticals and natural products, in one step from an alkenyl thioester. Unlike a potentially labile alkenyl thiol, an alkenyl thioester is stable and easy to prepare. The powerful Co catalysis via a cobalt hydride hydrogen atom transfer and radical-polar crossover mechanism enabled simultaneous cyclization and deprotection. The substrate scope was expanded by the extensive optimization of the reaction conditions and tuning of the thioester unit.</div>

Catalytic Synthesis of Cyclic Guanidines via Hydrogen Atom Transfer and Radical-Polar Crossover

2020 ◽  
Author(s):  
Shunya Ohuchi ◽  
Hiroki Koyama ◽  
Hiroki Shigehisa
Keyword(s):  
Hydrogen Atom ◽  
Functional Group ◽  
Hydrogen Atom Transfer ◽  
Catalytic Synthesis ◽  
Membered Ring ◽  
Biologically Active ◽  
Atom Transfer ◽  
Powerful Method ◽  
Protective Groups ◽  
The Common

A catalytic synthesis of cyclic guanidines, which are found in many biologically active compounds and natu-ral products, was developed, wherein transition-metal hydrogen atom transfer and radical-polar crossover were employed. This mild and functional-group tolerant process enabled the cyclization of alkenyl guanidines bearing common protective groups, such as Cbz and Boc. This powerful method not only provided the common 5- and 6-membered rings but also an unusual 7-membered ring. The derivatization of the products afforded various heterocycles. We also investigated the se-lective cyclization of mono-protected or hetero-protected (TFA and Boc) alkenyl guanidines and their further derivatiza-tions.

Sulfamides Direct Radical-Mediated Chlorination of Aliphatic C–H Bonds

2019 ◽  
Author(s):  
Melanie Short ◽  
Mina Shehata ◽  
Matthew Sanders ◽  
Jennifer Roizen
Keyword(s):  
Hydrogen Atom ◽  
Transfer Reaction ◽  
Hydrogen Atom Transfer ◽  
Chain Propagation ◽  
Propagation Mechanism ◽  
Atom Transfer ◽  
Radical Chain ◽  
Radical Intermediates ◽  
Transfer Processes ◽  
Unusual Position

Sulfamides guide intermolecular chlorine transfer to gamma-C(sp<sup>3</sup>) centers. This unusual position-selectivity arises because accessed sulfamidyl radical intermediates engage in otherwise rare 1,6-hydrogen-atom transfer processes. The disclosed chlorine-transfer reaction relies on a light-initiated radical chain-propagation mechanism to oxidize C(sp<sup>3</sup>)-H bonds.

Sulfamides Direct Radical-Mediated Chlorination of Aliphatic C–H Bonds

2019 ◽  
Author(s):  
Melanie Short ◽  
Mina Shehata ◽  
Matthew Sanders ◽  
Jennifer Roizen
Keyword(s):  
Hydrogen Atom ◽  
Transfer Reaction ◽  
Hydrogen Atom Transfer ◽  
Chain Propagation ◽  
Propagation Mechanism ◽  
Atom Transfer ◽  
Radical Chain ◽  
Radical Intermediates ◽  
Transfer Processes ◽  
Unusual Position

Sulfamides guide intermolecular chlorine transfer to gamma-C(sp<sup>3</sup>) centers. This unusual position-selectivity arises because accessed sulfamidyl radical intermediates engage in otherwise rare 1,6-hydrogen-atom transfer processes. The disclosed chlorine-transfer reaction relies on a light-initiated radical chain-propagation mechanism to oxidize C(sp<sup>3</sup>)-H bonds.

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