One of the more inefficient and wasteful synthetic transformations in the history of chemistry was the substitution reaction. While this type of reaction enabled countless molecules to be synthesized at the time, it required the use of a stoichiometric amount of a “leaving group” that left to become waste.

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In recent years, synthetic chemistry has developed a multitude of ways that are first steps in imagining the day when substitution reactions with all of their concomitant wastes are a thing of the past.