Exploiting Synergistic Effects in Organozinc Chemistry for Direct Stereoselective C‐Glycosylation Reactions at Room Temperature

Abstract

Pairing a range of bis(aryl) zinc reagents ZnAr2 with the stronger Lewis acidic [(ZnAr F 2)] (Ar F = C6F5), enables highly stereoselective cross-coupling between glycosyl bromides and ZnAr2 without the use of a transition metal. Reactions occur at room temperature with excellent levels of stereoselectivity, where ZnAr F 2acts as a non-coupling partner although its presence is crucial for the execution of the C(sp 2 )-C(sp 3 ) bond formation process.Mechanistic studies have uncovered a unique synergistic partnership between the two zinc reagents, which circumvents the need for transition-metal catalysis or forcing reaction conditions. Key to the success of the coupling is the avoidance of solvents that act as Lewis bases vs. diarylzinc compounds (e.g. THF).