Heterojunction‐based electron donators to stabilize and activate ultrafine Pt nanoparticles for efficient hydrogen atom dissociation and gas evolution

<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>

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Synthesis of Spongidine A, D and Petrosaspongiolide L Methyl Ester Using Pyridine C-H Functionalization

10.26434/chemrxiv.10303883 ◽

2019 ◽

Author(s):

Florian Bartels ◽

Manuela Weber ◽

Mathias Christmann

Keyword(s):

Natural Products ◽

Methyl Ester ◽

Hydrogen Atom ◽

Phospholipase A2 ◽

Late Stage ◽

Hydrogen Atom Transfer ◽

Ring System ◽

Tetracyclic Core ◽

Intramolecular Hydrogen ◽

Phospholipase A2 Inhibitors

<div>An efficient strategy for the synthesis of the potent phospholipase A2 inhibitors spongidine A and D is presented. The tetracyclic core of the natural products was assembled via an intramolecular hydrogen atom transfer‐initiated Minisci reaction. A divergent late‐stage functionalization of the tetracyclic ring system was also used to achieve a concise synthesis of petrosaspongiolide L methyl ester.</div>

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

10.26434/chemrxiv.13318421.v1 ◽

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.

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

10.26434/chemrxiv.8120654 ◽

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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