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Subtle differences in how pyridine is introduced can direct mechanochemical reactivity by enabling bond activation and favoring one reaction pathway over another. 

Layered solids (AsI₃, SbCl₃) can serve as templates for diastereomer formation, and mechanochemical variables can shift their ratios. 

Solution-based reactions are a staple of synthetic chemistry—but what happens mechanochemically, when thereisno solvent? 

Owing to the strength of the C–F bond, the ‘direct’ preparation of Grignard reagents, i.e., the interaction of elemental magnesium with an organic halide, typically in an ethereal solvent, fails for bulk magnesium and organofluorine compounds. Previously described mechanochemical methods for preparing Grignard reagents have involved ball milling powdered magnesium with organochlorines or bromines. Activation of the C–F bond through a similar route is also possible, however. For example, milling 1- and 2-fluoronaphthalene with an excess of magnesium metal for 2 h, followed by treatment with FeCl3 and additional milling, produces the corresponding binaphthalenes, albeit in low yields (ca. 20%). The yields are independent of the particular isomer involved and are also comparable to the yields from corresponding the bromonaphthalenes. These results may reflect similar charges that reside on the α-carbon in the naphthalenes, as indicated by density functional theory calculations. 

Ball milling CaI 2 and [KN(SiMe 3 ) 2 ] in a 1 : 1 ratio without solvent, and then extracting the ground material with toluene, yields the synthetically valuable neutral amide [Ca(N(SiMe 3 ) 2 ) 2 ] in good yield, without the contamination by calciate species that complicates solution metathesis routes. The effects on yield of grinding time, milling frequency, and calcium halide identity are also examined.