No abstract

Due to its good coordination ability to the metal compounds, chitosan and its derivatives can be used as a kind of good catalysts carrier. Recently, the catalytic properties of chitosan and its derivatives supported metal catalyst have been attracted more attentions. Based on the kind of reactions, the applications of chitosan and its derivatives supported metal catalysts in the catalytic asymmetric reaction, allylic substitution, coupling, addition, oxidation, reduction and some other reactions are reviewed. Keywords chitosans; chitosan derivatives; transition metal; catalytic reaction; asymmetric reaction 如制备壳聚糖衍生物及络合金属离子). 近年来壳聚糖 作为生物高分子广泛应用于 Pt、Ru、Rh 或 Pd 等贵金属 催化剂的载体 [20] , 其负载金属催化剂已经广泛应用在 氧化、还原、加成等反应中, 表现出优良的催化性 能 [21～23] . Guibal [24] 和 Macquarrie 等 [25] 对早期壳聚糖及其 衍生物负载的金属催化剂的形态结构、催化反应的研究 已经进行了详细地综述. 目前壳聚糖及其衍生物在催化 反应中主要用作催化剂的载体, 但其分子中的氨基可作 为有机碱, 在新近的报道中其本身也可以作为催化剂催 化反应 [26,27] . 本文以反应类型为主线, 对近年来壳聚糖 及其衍生物负载金属催化剂催化有机反应进行了综述.

The catalysts generated in situ from RuCl 2 (PPh 3) 3 and α-amino substituted benzimidazole derivatives L 1 ～L 4 were used to promote the reductive amination of acetophenone to generate α-phenylethylamine, N-(1-phenylethyl) formamide and α-phenylethanol. The bulkier substituent and phenyl group on the ligand will enhance the catalytic activity. The reductive amination of acetophenone was faster at 85 ℃, while the hydrogen transfer of acetophenone to α-phenylethanol became the main reaction at 125 ℃. The hydrogen and amine resouce is the ammonium formate. The plausible mechnism was proposed.

Chiral amine is a kind of important chemicals. Several L-amino acid based chiral diamines and triamines were prepared by ring-opening of substituted aziridines with L-amino acid esters in the matrix of silica without solvent. The ring-opening reactions were promoted by silica and accelerated by ultrasound radiation. The L-amino acid esters reacted with substituted aziridine 2 to give diamine 3 at first, then diamine 3 reacted with aziridine 2 again to form triamine 4. Compared with L-amino acid esters 1, compound 3 had a higher activity. (S)-Methyl pyrrolidine-2-carboxylate (1d) reacted with (R)-2-isopropyl-1-tosylaziridine (5) selectively yielding (S)-methyl 1-[(R)-3-methyl-2-(4-methylphenyl sulfonamide)butyl]pyrrolidine-2-carboxylate (6b) through the ring opening at 1,3-position of aziridine. All obtained compounds were characterized by 1 H NMR, 13 C NMR, IR and elemental analysis. 4c was analyzed by X-ray diffraction as well. Keywords amino acids; substituted aziridine; ring opening; solid phase synthesis; X-ray diffraction 1 结果与讨论 1.1 手性氨基酸衍生物的合成 我们首先尝试以 LiClO 4 为催化剂, L-苯丙氨基酸甲 酯(1a)在回流的乙腈中与 N-对甲基苯磺酰氮丙啶(2)的 开环反应, 经 TLC 监测, 20 h 后仍没有发生反应(Eq.

Glucosamine is a chiral compound degraded from widely existed natural product chitosan. It is becoming an ideal raw material for preparation chiral amine, amine/phosphine ligands due to its more chiral centers and strong coordination ability. The application of glucosamine derivatives as chiral ligands in asymmetric organic reactions has become a very active research area. In this paper, the application of glucosamine derivatives in asymmetric allylic alkylation, Heck reaction, 1,4-conjugate addition reaction, epoxidation reaction of olefins and cyclopropanation of olefin has been reviewed.