The use of immobilized crown ethers as in-situ N-protecting groups in organic synthesis and their application under continuous flow

<div> <div> <div> <p>Existing methods for making MIDA boronates require harsh conditions and complex procedures to achieve dehydration. Here we disclose that a pre-dried form of MIDA, MIDA anhydride, acts as both a source of the MIDA ligand and an in situ desiccant to enable a mild and simple MIDA boronate synthesis procedure. This method expands the range of sensitive boronic acids that can be converted into their MIDA boronate counterparts. Further utilizing unique properties of MIDA boronates, we have developed a MIDA Boronate Maker Kit which enables the direct preparation and purification of MIDA boronates from boronic acids using only heating and centrifuge equipment that is widely available in labs that do not specialize in organic synthesis. </p> </div> </div> </div>

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Visible Light-Mediated Oxidative Debenzylation

10.26434/chemrxiv.13135814 ◽

2020 ◽

Author(s):

Cristian Cavedon ◽

Eric T. Sletten ◽

Amiera Madani ◽

Olaf Niemeyer ◽

Peter H. Seeberger ◽

...

Keyword(s):

Reaction Time ◽

Visible Light ◽

Functional Groups ◽

Continuous Flow ◽

Protecting Groups ◽

Benzyl Ether ◽

Complex Molecules ◽

Protective Groups ◽

Benzyl Ethers ◽

Harsh Conditions

Protecting groups are key in the synthesis of complex molecules such as carbohydrates to distinguish functional groups of similar reactivity. The harsh conditions required to cleave stable benzyl ether protective groups are not compatible with many other protective and functional groups. The mild, visible light-mediated debenzylation disclosed here renders benzyl ethers orthogonal protective groups. Key to success is the use of 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) as stoichiometric or catalytic photooxidant such that benzyl ethers can be cleaved in the presence of azides, alkenes, and alkynes. The reaction time for this transformation can be reduced from hours to minutes in continuous flow. <br>

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Recent advances in Minisci-type reactions and applications in organic synthesis

Current Organic Chemistry ◽

10.2174/1385272824999201230211157 ◽

2020 ◽

Vol 24 ◽

Author(s):

Wengui Wang ◽

Shoufeng Wang

Keyword(s):

Free Radical ◽

Hydrogen Atom ◽

Organic Synthesis ◽

Radical Reactivity ◽

Atom Loss ◽

Radical Generation ◽

In Situ Generation ◽

Thermal Cleavage ◽

Synthetic Chemist

Abstract:: Minisci-type reactions have become widely known as reactions that involve the addition of carbon-centered radicals to basic heteroarenes followed by formal hydrogen atom loss. While the originally developed protocols for radical generation remain in active use today, in recent years by a new array of radical generation strategies allow use of a wider variety of radical precursors that often operate under milder and more benign conditions. New transformations based on free radical reactivity are now available to a synthetic chemist looking to utilize a Minisci-type reaction. Radical-generation methods based on photoredox catalysis and electrochemistry, which utilize thermal cleavage or the in situ generation of reactive radical precursors, have become popular approaches. Our review will cover the remarkably literature that has appeared on this topic in recent 5 years, from 2015-01 to 2020-01, in an attempt to provide guidance to the synthetic chemist, on both the challenges that have been overcome and applications in organic synthesis.

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