Selective Formylation and Methylation of Amines using Carbon Dioxide and Hydrosilane Catalyzed by Alkali-Metal Carbonates

Abstract

The formylation and methylation of amines with carbon dioxide and hydrosilanes are emerging yet important types of transformations for CO2. Catalytic methods effective for both reactions with wide substrate scopes are rare because of the difficulty in controlling the selectivity. Herein, we report that simple and readily available inorganic basesalkali-metal carbonates, especially cesium carbonatecatalyze both the formylation and methylation reactions efficiently under mild conditions. The selectivity can be conveniently controlled by varying the reaction temperature and silane. A “cesium effect” on both reactions was observed by comparing the catalytic activity of various alkali-metal carbonates. Combined experimental and computational studies suggested the following reaction mechanism: (i) activation of Si–H by Cs2CO3, (ii) insertion of CO2 into Si–H, (iii) formylation of amines by silyl formate, and (iv) reduction of formamides to methylamines.

Amorphous physics and materials: Secondary relaxation and dynamic heterogeneity in metallic glasses: A brief review

“…Strikingly, compelling experimental evidence was provided more recently that there exists a pronounced faster β' relaxation in rare earth based amorphous alloys. [86,87] Fig .5 (a) shows the DMA results of the La56.16Ce14.04Ni19.8Al10 bulk metallic glass. [86] At the low temperature around 226 K, another notable relaxation peak is seen from the loss modulus, indicative of a broad distribution of relaxation times similar to the  relaxation.…”

“…[86,87] Fig .5 (a) shows the DMA results of the La56.16Ce14.04Ni19.8Al10 bulk metallic glass. [86] At the low temperature around 226 K, another notable relaxation peak is seen from the loss modulus, indicative of a broad distribution of relaxation times similar to the  relaxation. We should stress that the intensity of the secondary relaxation or slow  relaxation is usually around 10% of that of  relaxation.…”

“…Copyright (2012), with permission from Elsevier. Fig.5 (a) The emergence of two secondary relaxations in La56.16Ce14.04Ni19.8Al10 metallic glass on the isochronal spectrum of mechancial spectrosopy; [86] (b) Temperature dependence of the slow β-relaxation and the fast β'-relaxation measured at frequencies of 1, 2, 4, 8 and 16 Hz for Er55Co20Al25 metallic glass; [87] (c) The schematic illustration of mechanisms of mechanical relaxations in amorphous alloy. The red atoms represent the active atoms, and atoms surrounded by green dash line represent flow units.…”

Reduction of carbon dioxide and organic carbonyls by hydrosilanes catalysed by the perrhenate anion

“…[1][2][3] A variety of catalysts have been discovered and developed for this reaction, including complexes of Co, 4 Cu, [5][6][7][8] Ir, [9][10][11][12][13][14] Ni, [15][16][17] Pd/Pt, 18 Rh, 19 Ru, [20][21][22][23][24][25] Sc, 26 Zn, [27][28][29] and Zr, 30 frustrated Lewis pairs, [31][32][33][34][35][36] organocatalysts, [37][38][39][40][41][42] alkali metal carbonates, 43 and even polar solvents such as DMF. 38 These reactions result in various reduction products including silyl-formates, -acetals, andethers, CO, and methane.…”

Multiscale Model for the Dielectric Permittivity

“…Our model is completed by assuming a system having a multiple relaxation scenario triggered by cascade processes (see Figure 1). Examples can be found in systems such as metallic glasses [9], graphene [10], and semiconductors [11,12]. In this context, let us assume a small random elementary input ξ ℓ whose effect on the relaxation time at stage ℓ is proportional to ξ ℓ and to the cumulative effect…”