An interesting reaction variation was observed in conversions of aryl bromides with strongly electron-donating methoxy groups. There, the precise substitution pattern was decisive. While 4-methoxyphenyl bromide (1n) led to a similar result (59% yield of 2n) as 4-tolyl bromide (1a), moving the methoxy substituent to the meta-position decreased the yield to 40% for 3-methoxybenzoic acid (2o). The analysis of the product mixture revealed the reason. Concomitant to 2o, 10% of ketone 3o had been formed. Even more so, with 2methoxyphenyl bromide (1p), the expected acid was not obtained at all, but instead, 2,2'dimethoxybenzophenone (3p) was isolated in 27%. The trend of increased ketone formation with closer spatial proximity of the methoxy groups to the "site of reaction" was even more pronounced in the reaction with 2,5-dimethoxybenzylbromide (1q), which led to ketone 3q in 50% yield. Overall, this ketone formation was remarkable as Grignard reactions of carboxylic acid derivatives are prone to lead directly to the corresponding tertiary alcohols. Under the here applied mechanochemical conditions, however, the initially formed magnesium carboxylate appears to be relatively stable. This salt allows for another Grignard reagent to be added, and the resulting dimagnesiate salt remains intact until its hydrolysis by aqueous workup to furnish the symmetric ketone. As demonstrated above, gaseous CO2 is a suitable reagent for mechanochemical Grignard reactions, but its handling requires specialized ball mill equipment. Thus, applying a solid source of CO2 under those conditions appeared attractive. In this manner, the aforementioned technical challenges could be overcome, and mass transport issues arising from gas/solid reactions in the milling devices could be circumvented. The use of dry ice was excluded due to its property of attracting water through condensation hampering the desired organometallic reactivity. Inspired by the recent revival of sodium methyl carbonate (SMC) by Jessop, Snieckus and co-workers, we decided to explore the potential of this very attractive source of solid, pre-activated CO2 in mechanochemical Grignard reactions.