Dichlorine monoxide (C120) has long been known1 and has been the subject of some modern mechanistic2 and physical3 studies, but it has not been shown to be a useful reagent in synthetic chemistry. We have found that ClzO is a powerful and selective reagent for either side-chain or ring chlorination of deactivated aromatic substrates, and it gives excellent yields under mild conditions where conventional reagents fail or require harsh ...
