排序方式: 共有137条查询结果,搜索用时 343 毫秒
131.
Mahmood Tajbakhsh Majid. M. Heravi Setareh Habibzadeh 《Phosphorus, sulfur, and silicon and the related elements》2013,188(2):361-364
Primary and secondary trimethylsilyl ethers are efficiently and rapidly converted to their corresponding carbonyl compounds with supported potassium ferrate under microwave irradiation in solventless system. 相似文献
132.
Dongyin Chen Chang Xu Jie Deng Chunhuan Jiang Xiaoan Wen Lingyi Kong Ji Zhang Hongbin Sun 《Tetrahedron》2014
Proton-exchanged montmorillonite (H-mont) was found to be an eco-friendly and cost-effective catalyst for the generation of O-methylated quinone methides (QM) from the corresponding p or o-methoxybenzyl esters and ethers. Nucleophilic trapping of the O-methylated QM with arenes, alcohols, 1,3-dicarbonyl compounds, silyl enol ethers, and allylsilanes has been carried out, respectively, leading to eco-friendly benzylation reactions. Using this protocol, H-mont-mediated deprotection of PMB-protected esters and ethers have been realized for the first time. This work would pave the way for further exploration in O-alkylated QM that are of chemical and biological significance. 相似文献
133.
Trimethylsilylation of alcohols with hexamethyldisilazane (HMDS) catalyzed by V(HSO4)3 under mild and completely heterogeneous reaction condition is reported. The method is highly chemoselective for the protection of alcohols in the presence of phenols, amines and thiols. Also, the deprotection of trimethylsilyl ethers is performed in the presence of V(HSO4)3 at room temperature in good to high yields. 相似文献
134.
聚谷氨酸苄酯脱保护制备聚L-谷氨酸的正交实验研究 总被引:1,自引:0,他引:1
聚L-谷氨酸苄酯(PBLG)用体积分数为33%的HBr-醋酸溶液脱保护得到聚L-谷氨酸(PLGA). 采用正交实验研究了温度、时间、溶剂及33%HBr-醋酸溶液用量在脱保护过程中对聚L-谷氨酸分子量的影响. 结果表明, 反应温度越高, 时间越长, 溶剂二氯乙酸用量越大, PBLG降解越快, 得到的PLGA分子量越小; 33%HBr-醋酸溶液的影响则相反, 随着33%HBr-醋酸溶液用量的增加, 反应体系酸性减弱, PBLG溶解度降低, 肽键断裂减缓, PLGA分子量也就相对较大. 相似文献
135.
Margaret E. Olson 《Tetrahedron letters》2010,51(30):3969-6941
The deprotection of aromatic as well as conjugated acetals and ketals in water is catalyzed by iron(III) tosylate (1.0-5.0 mol %). Iron(III) tosylate is an inexpensive and readily available catalyst. The use of water, the most environmentally benign solvent, makes this procedure especially attractive for acetal deprotection. 相似文献
136.
Babasaheb P. Bandgar Vaibhav S. Sadavarte Lav S. Uppalla Rahul Govande 《Monatshefte für Chemie / Chemical Monthly》2001,132(3):403-406
Summary. A simple and versatile method for the synthesis of oximes, semicarbazones, and tosylhydrazones of aldehydes in the presence
of ketones without catalyst and solvent is presented.
Received June 28, 2000. Accepted (revised) August 25, 2000 相似文献
137.
Jin Liu Xingyu Liu Qi Liu Jing Cao Xinheng Lv Prof. Shaoru Wang Prof. Tian Tian Prof. Xiang Zhou Prof. Hexiang Deng 《Angewandte Chemie (International ed. in English)》2023,62(42):e202302649
A metal–organic framework (MOF) with mespores (2 to 50 nm) allows the inclusion of large biomolecules, such as nucleic acids. However, chemical reaction on the nucleic acids, to further regulate their bioactivity, is yet to be demonstrated within MOF pores. Here, we report the deprotection of carbonate protected RNA molecules (21 to 102 nt) to restore their original activity using a MOF as a heterogeneous catalyst. Two MOFs, MOF-626 and MOF-636 are designed and synthesized, with mesopores of 2.2 and 2.8 nm, respectively, carrying isolated metal sites (Ni, Co, Cu, Pd, Rh and Ru). The pores favor the entrance of RNA, while the metal sites catalyze C−O bond cleavage at the carbonate group. Complete conversion of RNA is achieved by Pd-MOF-626, 90 times more efficiently than Pd(NO3)2. MOF crystals are also removable from the aqueous reaction media, leaving a negligible metal footprint, 3.9 ppb, only 1/55 of that using homogeneous Pd catalysts. These features make MOF potentially suited for bioorthogonal chemistry. 相似文献