51299-82-2Relevant articles and documents
Electron-rich triarylphosphines as nucleophilic catalysts for oxa-Michael reactions
Boese, A. Daniel,Fischer, Susanne M.,Renner, Simon,Slugovc, Christian
supporting information, p. 1689 - 1697 (2021/08/03)
Electron-rich triarylphosphines, namely 4-(methoxyphenyl)diphenylphosphine (MMTPP) and tris(4-trimethoxyphenyl)phosphine (TMTPP), outperform commonly used triphenylphosphine (TPP) in catalyzing oxa-Michael additions. A matrix consisting of three differently strong Michael acceptors and four alcohols of varying acidity was used to assess the activity of the three catalysts. All test reactions were performed with 1 mol % catalyst loading, under solvent-free conditions and at room temperature. The results reveal a decisive superiority of TMTPP for converting poor and intermediate Michael acceptors such as acrylamide and acrylonitrile and for converting less acidic alcohols like isopropanol. With stronger Michael acceptors and more acidic alcohols, the impact of the more electron-rich catalysts is less pronounced. The experimental activity trend was rationalized by calculating the Michael acceptor affinities of all phosphine-Michael acceptor combinations. Besides this parameter, the acidity of the alcohol has a strong impact on the reaction speed. The oxidation stability of the phosphines was also evaluated and the most electron-rich TMTPP was found to be only slightly more sensitive to oxidation than TPP. Finally, the catalysts were employed in the oxa- Michael polymerization of 2-hydroxyethyl acrylate. With TMTPP polymers characterized by number average molar masses of about 1200 g/mol at room temperature are accessible. Polymerizations carried out at 80°C resulted in macromolecules containing a considerable share of Rauhut-Currier-type repeat units and consequently lower molar masses were obtained.
Synthesis and fluorescence studies on menthol-coumarin conjugates
Rao, H. Surya Prakash,Desai, Avinash
, p. 514 - 524 (2015/07/07)
A three-step protocol for synthesis of alcohol containing aliphatic natural products and coumarins has been described. The Blaise reaction of converting the nitrile to β-keto esters formed key-step in this protocol. The menthol-coumarin conjugates prepared for the first time are subjected to absorption and fluorescence emission studies. The studies reveal that menthol substitution has little influence on the absorption or emission characteristic of the chromophore. However, substitution of C(6)H or C(6)OMe of the coumarin with NEt2 has dramatic influence on both absorption and emission of the conjugate. Solvatochromic studies and analysis of Stoke shift data show that the menthol-coumarin conjugate with C(6)NEt2 stabilizes itself in dipolar push-pull structure in ground and excited states.
Addition of alcohols to acrylic compounds catalyzed by Mg-Al LDH
Teodorescu,Deaconu,Bartha,Z?voianu,Pavel
, p. 117 - 122 (2014/03/21)
This study reports the preparation of hydrotalcite with Mg/Al molar ratio 3 by co-precipitation under low suprasaturation conditions of Mg and Al nitrated solutions with Na2CO3 and NaOH at pH 10. The solid was thermally decomposed at 460°C in air atmosphere in order to obtain mixed oxides which, by means of memory effect, can reconstruct the hydrotalcite structure by hydration with bidistilled water. The hydrotalcite and reconstructed samples by memory effect were characterized by elemental analysis, powder XRD, DRIFT and TG-DTG. Determination of the catalysts surface base sites was made using a method based on the irreversible adsorption of organic acids with different pKa values and N2 adsorption-desorption isotherms. The catalytic activity of these solids was evaluated in 1,4-addition of saturated linear alcohols to different acrylic compounds. All these reactions arose with high selectivity in the desired product. No by-products were detected by means of GC-MS chromatography and 1H NMR.