Taking the previously optimised conditions for the use of gaseous CO2 as starting point, magnesium was activated with lithium hydroxide at 600 rpm for 60 min (step I), and after the subsequent addition (step II) of 4-tolyl bromide (1a), 2-MeTHF (2 equiv.) and SMC (1.5 equiv.), the resulting mixture was milled at 300 rpm for 45 min (Scheme 3). To our delight, aqueous workup and purification by column chromatography then led to 4-toluic acid (2a) in 40% yield. Compared to the method with gaseous CO2, this result was remarkable because first, by using SMC as electrophile the milling procedure was shortened by an entire step. Second, argon atmosphere was not required, and third, the overall process time was significantly shorter. In attempts to improve the yield of 2a by varying the milling time in step II (60 min and 15 min), the product amount remained essentially unchanged. Using more or less of SMC (2.0 equiv. and 1.0 equiv. versus 1.5 equiv. as before) reduced the yield of 2a (to 32% and 31%, respectively). Switching 2-MeTHF to THF, adding a flake of iodine in step I, and varying the ball size proved ineffective as well (for details, see the Supporting Information). Scheme 3. Scope of aryl and alkyl bromides in a mechanochemical Grignard reaction with SMC (1 mmol scale). Reaction conditions: Step I = Mg (2.50 mmol, 2.5 equiv.) and LiOH (2.75 mmol, 1.1 equiv.) in a ZrO2-M milling vessel (12 mL) with 3 ZrO2-M balls (Ø 9 mm); step II = addition of 2-MeTHF (2.00 mmol, 2.0 equiv.), SMC (1.50 mmol, 1.5 equiv.), and 1 (1.00 mmol). The yields refer to product amounts obtained after column chromatography.