Grinding auxiliary

Fritsch Planetary Micro Mill Pulverisette 7, stainless steels containers, eight trails, Ar purged, eOmin, aminoacrylate NaHC03 l-IC0 a r -BuJ IC Pd(0Ac)2 1.05 2.5 0.2 1.2 0.05, NaCI grinding auxiliary. 

Retsch MM200 ball mill, 30Hz, stainless steel grinding jar, ArX PhB(OH)2 NEt3 Pd (OAc)2 1 1 3 0.045, lOmln, NaCI grinding auxiliary. 

Fritsch Pulverlsette planetary ball mill, grinding beakers (45 mL, agate. ZrO-J, balls (6x 15mm), SOOrpm, 20min, Arl acetylene Pd(OAc)2 DABCO 2 2.5 0.05 2.5, ALJCs grinding auxiliary. 

Entry E Catalyst/ mol% Liquid/ iL Grinding Auxiliary Time/h Yield (%) ... 

Optimal reaction conditions were used for ball milling of stoichiometric amounts of variety of Boc-protected a-amino acid A-carboxyanhydrides (Boc-AA-NCA) 92 or Boc-protected a-amino acid A-hydroxysuccinimide esters (Boc-AA-OSu) 95 with a-amino acid alkyl ester salts (Schemes 3.26 and 3.27, Tables 3.9 and 3.10). In this way, di- to pentapeptides 97 and 100 were produced in high yield and environmentally benign manner. For some of the reactions, iBuOAc was used as a grinding auxiliary. Furthermore, it was established that no racemization could be observed as the diastereomeric excess of some products was checked and was found to be superior to 98%. After completion of Boc-AA-OSu reactions, mixture was milled for 5 min at 30 Hz with aqneous NaOH solution, diluted with EtOAc, and washed with sodium carbonate and dilnted acid. Pentapeptide Boc-Tyr(Bn)-Gly-Gly-Phe-Leu-OBn product obtained mechanochemically was successfully converted to Leu-enkephaUn by classical methods. 

Retsch MM400 mixer mill, 30Hz, stainless steel jar (lOmL), one 12mm milling ball, LAG nitromethane (r]=0.25f mg- ), acid amine EDC.HCI DMAP 1 1 1 2mol, WOmin, NaCI grinding auxiliary 20 equiv. isolated yield. 

Addition of amines to acetylene carboxylates 246 in ball mill was studied by Stolle and Thorwirth (Scheme 3.65) [44]. Employing solvent-free protocol in planetary ball mill in conjunction with quartz sand as inert grinding auxiliary, a number of enamines 247 were prepared in high yield (Table 3.33). No further catalysts or additives was required to accomplish reaction within 5 min. Obtained E/Z ratios vary with amine applied in the case of dicarboxylates, mainly the E-isomers have been identified. In contrast, reactions with propiolates and anilines yielded favorably the Z-isomer, whereas secondary alkyl amines furnished the E-isomer preferably. Simple stirring of DMAD and aniline in flask afforded only 80% conversion and chemoselectivity was lower (E/Zratio of 87 13) in comparison to ball milling. A common method for synthesis is the reaction in solvent, for which was found to have a strong influence on the E/Z ratio of the product, while this influence is not present in solvent-free milling. 

Planetary centrifugal mill AGO-2 (acceleration 60g), stainless steel vial 35mL. 5mm balls (75g), substrate hydrazlne NaHS04 10 2 0.2 mol, silica gel grinding auxiliary 10g. 

High chemoselectivity was obtained in solvent-free Cu°-catalyzed Ullmann-type Af-arylation reactions of iodobenzenes by Cravotto et al. (Scheme 3.100). [66]. In planetary ball-milling A-arylations reactions, stoichiometric amount of copper powder, an excess of base (KOH) and alumina as grinding auxiliary gave the best results. 

A detailed investigation on the influence of the type of oxidant and grinding auxiliary in the oxidation reactions of p-toluidine was carried out by Stolle et al. (Scheme 6.5) [6]. Notable differences between the oxidants, as well as significant differences for the same oxidant in combination with different grinding auxiliaries, were observed. This finding allowed the reaction to be directed toward all three major oxidation products (azo, azoxy, and nitro) by choosing the right combination of oxidant and... 

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