Stereospecific and stereoconvergent nucleophilic substitution reactions at tertiary carbon centers

Nucleophilic substitutions such as S(N)1 and S(N)2 are fundamental textbook reactions. Their stereoselective versions have been shown to be versatile in the preparation of enantiopure compounds. In this review, we discuss challenges surrounding achieving stereoinvertive S(N)2 and S(N)1 reactions at tertiary carbon centers. This is followed by discussions on stereoconvergent substitutions at tertiary carbon centers using strategies such as chiral- catalyst-directed S(N)1, radical-based nucleophilic substitution, and halogen-bonding-assisted S(N)2X reactions. Mechanistic discussions provide insights on how these reactions can be differentiated.