Mechanistic Study 何 龙 2009-12-26

Mechanistic Study

何 龙

2009-12-26

• in situ IR• NMR• MS• deuterium label• Kinetic• cirrcular dichroism spectra• Trap the intermediate• NLE

内容提要

ReactIR 4000 适用于实验室使用，采用傅立叶变换红外（ FTIR ）技术，通过测量物质的红外区域的特征“指纹”光谱，探头浸入反应物中直接测量红外吸收，可在线实时跟踪和分析反应过程，跟踪反应物、中间物和产物的瞬时变化，提供反应过程和反应组成的“实况” , 从而测定反应成分（反应物、产物及中间产物）的相对浓度变化，提供反应趋势、终点和各个过程的％转化率 , 得到反应机理的详细信息。

1. 工作温度范围： -80—250℃2. 工作压力范围： 13mbar—350bar 3. 主机测试范围： 400—4800cm-1 4. 分辨率： 1cm-1 5. 精确度： 0.02cm-1

in situ IR

Enantioselective and Diastereoselective Mukaiyama-MichaelReactions Catalyzed by Bis(oxazoline) Copper(II) Complexes

David A. Evans, J. Am. Chem. Soc. 2001, 123, 4480-4491

Dynamic Ligand Exchange of the Lanthanide Complex Leading to Structural and Functional Transformation: One-Pot Sequential Catalytic Asymmetric Epoxidation-Regioselective Epoxide-Opening Process

Masakatsu Shibasaki, J. AM. CHEM. SOC. 2005, 127, 2147-2155

In situ IR experiments. (A) Me3SiN3 (20 mol equiv) + Sm(O-i-Pr)3 (1 mol equiv).

Me3SiN3 (20 mol equiv) + (S)-Sm complex-1(1 mol equiv).

When Sm(O-i-Pr)3 (1 mol equiv) and Me3SiN3 (5 mol equiv) were mixed in THF-d8, thegeneration of Me3SiO-i-Pr was observed on 1H and 13C NMR spectra, suggesting that a ligand exchange occurs from the isopropoxide to the azide on the samarium metal.

Sm(N3)3 has an absorption at 2093 cm-1 (N=N stretch). Sm(N3)2(OMe) at 2082 , SmN3(OMe)2 2083 cm-1,

The broad peak at 2072 cm-1 corresponds to the samarium azide complex

kinetic

Initial Rate Kinetics on the Concentration of Catalyst [Sm(O-i-Pr)3]

Initial Rate Kinetics on the Concentration of Me3SiN3

NMR 仪可进行核的动态过程、瞬变过程、反应动力学等方面的研究，是鉴定有机化合物、金属有机化合物、生物样品、高分子材料、药物等的结构、构型和构象的重要工具，还可应用与定量分析、相对分子量的测定和化学动力学等研究。

NMR

Bruker AV II-400 MHz

Scope and Mechanism of Enantioselective Michael Additions of 1,3-Dicarbonyl Compounds to Nitroalkenes Catalyzed by Nickel(II)-Diamine Complexes

David A. Evans, J. AM. CHEM. SOC. 2007, 129, 11583-11592

Dual role

This result is consistent with our kinetic studies that show that the reaction is first order in metal complex

Figure 7. Kinetic studies on the addition of diethyl malonate to nitrostyrene: (A) excess diethyl malonate; (B) excess nitrostyrene.

Proposed Reaction Mechanism

Hydrogen-Bonding Directed Reversal of Enantioselectivity

Yong-Gui Zhou, J. AM. CHEM. SOC. 2007, 129, 750-751

Catalytic Asymmetric Epoxidation of Enones Using La-BINOL-Triphenylarsine Oxide Complex: Structural Determination of the Asymmetric Catalyst

Masakatsu Shibasaki, J. Am. Chem. Soc. 2001, 123, 2725-2732

The catalytic asymmetric epoxidation of enones using the La-BINOL-Ph3AsdO complex generated from La(O-i-Pr)3, BINOL, and Ph3As=O in a ratio of 1:1:1

ESI-MS

X-ray-gradecrystal from the complexes’ solution generated from La(O-i-Pr)3, BINOL, and Ph3AsdO in a ratio of 1:1:3, containing an excess amount of Ph3As=O relative to the best ratio for the asymmetric epoxidation.

Deductions:

(i) The same complex should exist under all conditions and function as the most active and effective catalyst.(ii) The generation rate of the most active catalyst might be different in each case.(iii) Although the La-BINOL-Ph3As=O complex generated in a ratio of 1:1:1 was the best one for

the epoxidation, the major component existing in the solution would be the 1:2:2 complex 7.

1:1:1 or 1:2:2

Figure 7. Kinetic experiments of the epoxidations using 6 mol % of the La-(R)-BINOL-Ph3AsdO complex in a ratio of 1:2:2 with x mol % of La(O-i-Pr)3.

Managing Highly Coordinative Substrates in Asymmetric Catalysis: A Catalytic Asymmetric Amination with a Lanthanum-Based Ternary Catalyst

Masakatsu Shibasaki, J. AM. CHEM. SOC. 2009, 131, 14990–14999

D and L

oligomericLa/3a monometallic La

Figure 2. Kinetic profiles of the asymmetric amination of 7c promoted by La(NO3)3•6H2O/(R)-3a/base ) 1/1/3 catalyst. The reactions were run with [7c]) 100 mM, [BocN)NBoc] ) 120 mM, [La(NO3)3•6H2O] ) 2.5 mM, [(R)-3a] ) 2.5 mM, and [base] ) 7.5 mM (4 mol % of catalyst loading based on La).b: base ) H-D-Val-O tBu (corresponds to Table 4, entry 1), 9: base ) Et3N (entry 2), 2: base ) Cs2CO3 (entry 3), 0: base ) H-D-Val-O tBu/Et3N (1/2) (entry 4), O: base ) H-D-Val-OtBu/Cs2CO3 (1/2) (entry 5).

ESI TOF MS analysis of La(NO3)3•6H2O/(R)-3a/H–D-Val–OtBu/Et3N = 1/1/1/2 solution.

ESI TOF MS analysis of La(NO3)3•6H2O/(R)-3a/H–D-Val–OtBu/7c = 1/1/3/5 solution.

Jasco-J-810 圆二色光谱仪，是根据圆二色光谱法的原理和测试要求以波长、时间、温度、 pH 值和浓度为函数设计制成的仪器，目前圆二色光谱法及其仪器已广泛应用于有机化学、生物化学、配位化学和药物化学等领域，成为研究有机化合物的立体构型的一个重要方法。

光谱扫描范围： 163 nm~900 nm

cirrcular dichroism spectra

Highly Enantioselective Oxidative Couplings of 2-Naphthols Catalyzed by Chiral Bimetallic Oxovanadium Complexes with Either Oxygen or Air as Oxidant

Hirokazu Urabe, J. AM. CHEM. SOC. 2009, 131, 3166–3167

Rh-Catalyzed Isomerization and Intramolecular Redox Reaction of Alkynyl Ethers Affording Dihydropyrans and Ketoolefins

A New Entry to Cascade Organocatalysis: Reactions of Stable Sulfur Ylides and Nitroolefins Sequentially Catalyzed by Thiourea and DMAP

Wen-Jing Xiao, J. AM. CHEM. SOC. 2008, 130, 6946–6948