Permeable Reactive Barriers in Europe

Mechanochemical Birch Reduction with Low Reactive Alkaline Earth Metals

“…occurred similarly but produced 1 b as the main product (44 % yield) due to an excess of the metal. The facile reductive dechlorination of compounds 25 a and 26 a is consistent with the prior work of Rowland [32a] and Birke [32b] on mechanochemical destruction of chlorinated pollutants. The trifluoromethyl group of 3‐(trifluoromethyl)benzoic acid ( 27 a ) was smoothly dehalogenated with Mg metal, yielding a mixture of 3 a and 3 b (eq.…”

Mechanochemical Simmons–Smith cyclopropanationviaball-milling-enabled activation of zinc(0)

“…using a mixer mill at 30 Hz for 1 hour gave promising yields of the cyclopropanated product 3a (Scheme 2, entry 1, 59%). Our previous work 9 on mechanochemical organozinc formation has demonstrated that the addition of N , N′ -dimethylacetamide (DMA) as a liquid assisted grinding additive proved crucial to high reaction efficiency. In this case, whilst a pleasing increase was observed on the addition of DMA (entry 2, 76%, 2.5 equivalents of DMA), further improvement was observed on employing more environment-acceptable alternatives 2-MeTHF (entry 4, 83%), and EtOAc (entry 5, 81%).…”

“…These procedures can be carried out without need of exogenous activation procedures, 8 bypassing pyrophoric intermediates such as finely ground magnesium, 9 all under air atmospheres, and in the absence of bulk solvent. Using this technology, our group has leveraged protocols for the ball-milling-enabled Negishi, 10 Reformatsky, 11 and Barbier 12 reactions (Scheme 1B).…”

Synthesis without solvent: consequences for mechanochemical reactivity

“…44 Birke and coworkers used ball milling to dechlorinate 1,3,5-chlorobenzene to benzene through in situ Grignard formation, followed by reduction with n-butyl amine as the H donor. 45 Our group used mechanochemistry to study the activation of C-F bonds with Mg. 46 Ito and coworkers were the first to prepare and use Grignard reagents under air; the Grignard reagent could be isolated and combined with a variety of electrophiles to produce coupled products without the need for inert atmosphere. 47 The yield is low for a strictly dry reaction (e.g., 6% yield for the nucleophilic addition product derived from the reaction of bromobenzene and Mg with benzaldehyde), and LAG with THF improves the yield to 490%.…”