Continuous Chemoselective Methylation of Functionalized Amines and Diols with Supercritical Methanol over Solid Acid and Acid−Base Bifunctional Catalysts

Abstract

The selective N-methylation of bifunctionalized amines with supercritical methanol (scCH(3)OH) promoted by the conventional solid acids (H-mordenite, beta-zeolite, amorphous silica-alumina) and acid-base bifunctional catalysts (Cs-P-Si mixed oxide and gamma-alumina) was investigated in a continuous-flow, fixed-bed reactor. The use of scCH(3)OH in the reaction of 2-aminoethanol with methanol (amine/CH(3)OH = 1/10.8) over the solid catalysts led to a significant improvement in the chemoselectivity of the N-methylation. Among the catalysts examined, the Cs-P-Si mixed oxide provided the most efficient catalyst performance in terms of selectivity and reactivity at 300 degrees C and 8.2 MPa; the N-methylation selectivity in the products reaching up to 94% at 86% conversion. The present selective methylation was successfully applied to the synthesis of N-methylated amino alcohols and diamines as well as O-methylated ethylene glycol. Noticeably, ethoxyethylamine was less reactive, suggesting that the hydroxy group of the amino alcohols is a crucial structural factor in determining high reactivity and selectivity, possibly because of the tethering effect of another terminus, a hydroxo group, to the catalyst surface. The magic-angle-spinning NMR spectroscopy and X-ray diffraction analysis of the Cs-P-Si mixed oxide catalyst revealed that the acidic and basic sites originate from P(2)O(5)/SiO(2) and Cs/SiO(2), respectively, and the weak acid-base paired sites are attributed to three kinds of cesium phosphates on SiO(2). The weak acid-base sites on the catalyst surface might be responsible for the selective dehydrative methylation.

Asymmetric reduction of ketones by Geotrichum candidum: immobilization and application to reactions using supercritical carbon dioxide

“…The immobilized cell (2.5 g) was packed in an up-flow tubular reactor (1/2 inch  10 mm  135 mm), 11 and substrate solution (1 (0.011 M), 2-propanol (12.72 M), and NAD + (1.2  10 À5 M) in an MES buffer (0.10 M, pH 7.0)) was pumped (JASCO, PU-2085) at the rate of 0.15 mL/min. The system reached equilibrium after 3 h, and then the product was analyzed by GC using undecane as an internal standard.…”

Solvothermal Synthesis and Catalytic Properties of Nanocrystalline ZnFe2−xAlxO4 (x = 0, 1, 2) Spinels in Aniline Methylation

“…The first one is traditional route based on the application of corrosive acids or conventional Friedel-Crafts systems [5,6], zeolites [7,8], onium salts [9] as catalysts and alkyl halides or dimethyl sulphate as alkylating agents [10]. The second one is environmentally more benign process using solid catalysts such as metal oxides, aluminium and magnesium phosphates, clays, zeolites and others [11][12][13][14][15][16][17][18][19][20][21][22]. During catalytic aniline methylation, methanol as well as dimethyl carbonate (DMC) are used as alkylating agent [8,23].…”

A novel co-production process for piperazine and its N-monoalkyl derivatives

“…Recently, piperazine has been synthesized by catalytic amination of ethanolamine as a byproduct or from the catalytic cyclization of N-b-hydroxyethyl-1,2-ethylenediamine (HEEDA) [6][7][8][9][10][11][12]. N-monoalkylpiperazines are obtained from piperazine via nucleophilic substitution by haloalkanes or by reductive amination of alcohols, aldehydes, or ketones [1,[13][14][15][16].…”