Photocatalytic synthesis of acetals and ketals from aldehydes and silylenolethers without the use of acids

Autor: Desirée Steuernagel, Hans‐Achim Wagenknecht
Rok vydání: 2022
Předmět:
Zdroj: Chemistry – A European Journal, 29 (13), Art.-Nr.: e202203767
ISSN: 1521-3765
0947-6539
Popis: Acetals and ketals are among the most important protecting groups for carbonyl compounds. A new method for the acetalization and ketalization was developed by means of photoredox catalysis. The biscyanolated perylene bisimide is used as electron-poor photocatalyst, together with green light (525 nm LED). Silylenolethers derived from aldehydes react efficiently to acetals in good to excellent yields. A broad substrate range was shown with respect to both the aldehydes and the alcohols. The functional group tolerance is high. Especially acid- and hydrogen-labile protecting groups are tolerated. Aldehydes can also be directly and selectively converted into the respective acetals. Only ketones must be converted to their silylenolethers before ketalization. This photocatalytic method works completely without the use of acids or photoacids, and does not need any additives or H-atom transfer reagents. Hence, it broadens the substrate scope and repertoire of photo-redox catalysis with respect to carbonyl chemistry.
Databáze: OpenAIRE
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