Ketones and Aldehydes as Alkyl Radical Equivalents for C–H Functionalization of Heteroarenes
Qingmin Wang describes the C–H functionalization of heteroarenes using ketones and aldehydes.
The use of aldehydes as umpolung nucleophilic reagents is a classic strategy in synthetic organic chemistry, which has complemented the use of carbonyl compounds as electrophilic partners in countless reactions with a very broad range of organometallic reagents, ylides and other nucleophiles. There have also been reports of aldehydes used as alkyl radicals, resulting from oxidative decarbonylation. However, the use of aldehydes and ketones as radical equivalents in which the radical is centered on the carbonyl carbon is far less common, and the viability of such an innovative approach has been recently investigated in a paper published by the group of Professor Qingmin Wang at Nankai University (Tianjin, P. R. of China). The authors have developed a new catalytic activation mode that involves a combination of Proton Coupled Electron Transfer (PCET) and a RiboNucleotide Reductase (RNR) class I reaction to enable C–H alkylation of heteroarenes using ketones and aldehydes as alkyl radical sources under mild conditions, without the need for oxidants or high temperatures.