Unsymmetric salen ligands bearing a Lewis base: intramolecularly cooperative catalysis for cyanosilylation of aldehydes
作者:Ye-Qian Wen、Wei-Min Ren、Xiao-Bing Lu
DOI:10.1039/c1ob05695f
日期:——
A series of unsymmetric salen ligands derived from 1,2-diaminocyclohexane bearing an appended Lewis base on the three-position of one aromatic ring were synthesized by the reaction of various functional salicyaldehydes with the condensation product of 1,2-diaminocyclohexane mono(hydrogen chloride) and 3,5-di-tert-butylsalicylaldehyde. These ligands in conjunction with Ti(OiPr)4 exhibited excellent activity in catalyzing the cyanosilylation of aldehydes with trimethylsilyl cyanide (TMSCN) at mild conditions. The highest activity was observed in the catalyst system with regard to the salen ligand bearing a diethylamino group, which proved to be active even at a high [aldehyde]/[catalyst] ratio up to 50000. In a low catalyst loading of 0.05 mol%, the quantitative conversion of benzaldehyde to the corresponding cyanosilylation product was found within 10 min. at ambient temperature. An intramolecularly cooperative catalysis was proposed wherein the central metal Ti(IV) is suggested to play a role of Lewis acid to activate aldehydes while the appended Lewis base to activate TMSCN.
Described are our preliminary studies on the reactivity of thiophosphate in a setting which correlates with the cyanosulfidic systems chemistry we have previously reported. Thiophosphate adds to various nitrile groups giving the corresponding thioamides in a highly efficient manner and the mechanistic implications are briefly discussed. Thiophosphate can also act as a phosphorylating agent, which was
Cyanohydrins (α-hydroxy nitriles) are a special type of nitriles that readily decompose into hydrogen cyanide (HCN) and the corresponding carbonyl compounds. Hydration of cyanohydrins that are readily available through cyanation of aldehydes and ketones provides the most straightforward route to valuable α-hydroxyamides. However, due to low stability of cyanohydrins and deactivation of the catalysts
Indium trifluoride promoted chemoselective additions of TMSCN to various aldehydes in water gave the respective cyanohydrins in good yields.
三氟化铟促进的TMSCN对多种醛在水中的化学选择性加成反应,以良好产率得到了相应的氰醇。
Studies on Phosphoroheterocycle Chemistry III: An Unusual Way to 1,3,2-Thiazaphospholidine-4-thione 2-Sulfide Derivatives
作者:ShengLou Deng、RuYu Chen
DOI:10.1055/s-2002-35619
日期:——
An unusual but efficient method for the synthesis of phosphoroheterocycles, 1,3,2-thiazaphospholidine-4-thione 2-sulfide derivatives, by the reaction of Lawesson'sreagent with a variety of u-hydroxy nitriles has been developed. The possible mechanism of the reaction is proposed to involve thiation of hydroxy group in a first step, sequential addition of P-SH to the nitrile and rearrangement resulting