Rapid Wolff–Kishner reductions in a silicon carbide microreactor

Abstract

Wolff-Kishner reductions are performed in a novel silicon carbide microreactor. Greatly reduced reaction times and safer operation are achieved, giving high yields without requiring a large excess of hydrazine. The corrosion resistance of silicon carbide avoids the problematic reactor compatibility issues that arise when Wolff-Kishner reductions are done in glass or stainless steel reactors. With only nitrogen gas and water as by-products, this opens the possibility of performing selective, large scale ketone reductions without the 10 generation of hazardous waste streams.

Organic reactions for the electrochemical and photochemical production of chemical fuels from CO2 – The reduction chemistry of carboxylic acids and derivatives as bent CO2 surrogates

“…High temperatures are required, and the transformation is incompatible with hydrolysis-prone substrates such as esters, lactams, lactones, amides, etc. Examples of side-reactivity include the incomplete reduction of the carbonyl group to an alcohol rather than the alkane, as well as elimination reactions and double-bond isomerizations [114].…”

Continuous‐Flow Technology—A Tool for the Safe Manufacturing of Active Pharmaceutical Ingredients

“…It condenses with various bifunctional electrophiles to generate valuable heterocycles such as indoles,pyrazoles,and triazoles,k ey building blocks for the preparation of av ast range of pharmaceuticals.J ensen and co-workers used a4 70 mLs ilicon carbide (SiC) microreactor to perform aW olff-Kishner reduction (Scheme 48 a). [172] SiC is an almost completely corrosion-resistantm aterial which, furthermore,e xhibits excellent heat stability and thermal conductivity.T he reactions were conducted at 200 8 8Cw ith only 1.5 equivalents of hydrazine hydrate and 3equiv of KOH. A3 to 15 min residence time was enough to convert the carbonyl functionalities of several ketones into methylene groups (76-96 %y ield).…”

Kontinuierliche Durchflussverfahren: ein Werkzeug für die sichere Synthese von pharmazeutischen Wirkstoffen

“…[172] Siliciumcarbid ist ein weitgehend korrosionsbeständiges Material, das außerdem eine ausgezeichnete Wärmebeständigkeit und Wärmeleitfähigkeit aufweist. Die Reaktionen wurden bei 200 8 8Cm it nur 1.5 ¾quiv.…”

“…Diese außergewçhnliche Produktivität ist mçglich aufgrund der Kombination von hoher physikalischer und chemischer Stabilität des Reaktormaterials neben dem nicht vorhandenen Reaktordampfraum in dem unter Druck stehenden System. [172] Eine direkte palladiumkatalysierte C-N-Kreuzkupplung von Arylchloriden mit Hydrazin wurde durch die Gruppe von Buchwald entwickelt (Schema 48 b). [173] So wurden Lçsungen von Präkatalysator,A rylchlorid, Hydrazin und Base nacheinander zugemischt und bei Raumtemperatur in eine erste Verweileinheit eingeleitet.…”