Abstract
Despite recent advances in solid-state organic synthesis using ball milling, insight
into the unique reactivity of solid-state substrates, which is often different from
that in solution, has been poorly explored. In this study, we investigated the relationship
between the reactivity and melting points of aryl halides in solid-state Suzuki–Miyaura
cross-coupling reactions and the effect of reaction temperature on these processes.
We found that aryl halides with high melting points showed significantly low reactivity
in the solid-state cross-coupling near room temperature, but the reactions were notably
accelerated by increasing the reaction temperature. Given that the reaction temperature
is much lower than the melting points of these substrates, the acceleration effect
is most likely ascribed to the weakening of the intermolecular interactions between
the substrate molecules in the solid state. The present study provides important perspectives
for the rational design of efficient solid-state organic transformations using ball
milling.
Key words
cross-coupling - solid state - mechanochemistry - ball milling - palladium catalyst
