Exploiting synergistic effects in organozinc chemistry for direct stereoselective C‐glycosylation reactions at room temperature

Hernan-Gomez, Alberto and Orr, Samantha and Uzelac, Marina and Kennedy, Alan and Barroso, Santiago and Jusseau, Xavier and Lemaire, Sebastien and Hevia, Eva (2018) Exploiting synergistic effects in organozinc chemistry for direct stereoselective C‐glycosylation reactions at room temperature. Angewandte Chemie International Edition. ISSN 1433-7851 (https://doi.org/10.1002/anie.201805758)

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Abstract

Pairing a range of bis(aryl) zinc reagents ZnAr2 with the stronger Lewis acidic [(ZnArF2)] (ArF = 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 ZnArF2 acts as a non‐coupling partner although its presence is crucial for the execution of the C(sp2)‐C(sp3) 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)

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