Catalyzed self-aldol reaction of valeraldehyde via a mechanochemical method

Solvent-free and time-efficient Suzuki–Miyaura reaction in a ball mill: the solid reagent system KF–Al2O3under inspection

“…The reported results also confute the results from microwave-assisted cross-coupling with pure basic alumina, which was seen to be completely inert for this type of reaction [33]. Apparently co-grinding of all reactants in a ball mill leads to in situ activation, which enhances the capability of aluminas to act as a base in Suzuki–Miyaura reactions probably because of the generation of new highly active surfaces [59] including the defect sites that allow the activation of the boronic acid as mentioned above.…”

Antimony(v) cations for the selective catalytic transformation of aldehydes into symmetric ethers, α,β-unsaturated aldehydes, and 1,3,5-trioxanes

“…This indicated to us that there is a strong interaction between the phosphorus and antimony centers owing to the high Lewis acidity of the cationic antimony atom. In agreement with this assessment, we note that the P1-Sb1-C21 angle of 170.18 (14)° is consistent with donation of the phosphorus atom lone pair into a low-lying Sb1-C21 σ* orbital. In addition, we noticed that the triflate counter ion is weakly coordinated to the P1-Sb1 unit as evidenced by the Sb1-O1 distance (2.812 Å), the O1-Sb1-C31 angle (166.8°), the P1-O1 distance (3.661 Å), and the O1-P1-C51 angle (158.6°).…”

“…10 For example, the synthesis of aliphatic or aromatic ethers, which are found in many useful natural products, 11 are valuable building blocks for fine chemicals, polymers and dyes, 12 relies primarily on the Williamson synthesis whereby an alkoxide is coupled to an alkyl halide/sulfonate under basic conditions. 13, 14 However the large amount of chemical waste, specifically the salt byproduct, 15 has been associated with environmental soil and ground water contamination. 16 Alternative methodologies that involve the direct reductive homocoupling of aldehydes was recently reported using organosilicon reagents such as Et 3 SiH, Me 3 SiH, PhSiH 3 , polymethosihydrosilane, (PMHS) and tetramethyldisiloxane (TMDS) as reducing agents in the presence of Lewis acid catalysts, including BiBr 3 , 17 I 2 , 18 Triflic acid, 19 Cu(OTf) 2 , 20 In(OTf) 3 .…”

Metal-catalyzed organic reactions using mechanochemistry

“…Examples of such metalmediated reactions include the oxidative homocoupling of phenols catalyzed by FeCl 3 ·6H 2 O, 84 the Mn(OAc) 3 -mediated formation of benzofuranone and dihydrobenzofuran derivatives, 85 the mechanochemical self-aldol reaction of valeraldehyde facilitated by aluminum, 86 the chlorination of hydrocarbons by CuCl 2 in a ball mill 87 and reduction of nitro groups by elementary metals. 88 Due to the space limitations, and the existence of excellent reviews and studies addressing such reactions in more detail, 1,89 we have decided to highlight only the most recent contributions to this field.…”