Cysteine is one of the least abundant amino acids in proteins of many organisms, which plays a crucial role in catalysis, signal transduction, and redox regulation of gene expression. The thiol group of cysteine possesses the ability to perform nucleophilic and redox-active functions that are not feasible for other natural amino acids. Cysteine is the most common covalent amino acid residue and has been shown to react with a variety of warheads, especially Michael receptors. These unique properties have led to widespread interest in this nucleophile, leading to the development of a variety of cysteine-targeting warheads with different chemical compositions. Herein, we summarized the various covalent warheads targeting cysteine residue and their application in drug development.

A novel photocatalytic acylarylation of unactivated alkenes using diaryliodonium salts as the arylation reagent is described. The reaction produces a variety of 2-benzyl indanones, 3,4-dihydronaphthalen-1(2H)-ones, and 2,3-dihydroquinolin-4(1H)-ones in promising yields with excellent diastereoselectivity under very mild conditions, which may be appealing for the synthesis of biologically active molecules.

In this work, we developed a novel method to synthesize 1,1,2-tribromoethyl arenes, which can be easily transformed to 1-bromoalkynes via base-mediated elimination reaction. The bromination reagent was in situ generated from the reaction of NaBr/NaBrO₃/H₂SO₄, resulting in high reactivity, excellent chemical selectivity and outstanding functional group tolerance. Moreover, 1,1,2-tribromoethyl arenes encounter a selectivity switch to afford α-bromoketones under strong acidic conditions.