多立体中心（硫）脲催化剂催化不对称杂原子迈克尔加成反应的理论研究

【作者】 王慧；

【导师】 陈德展；

【作者基本信息】 山东师范大学 ， 物理化学， 2011， 硕士

【摘要】 手性是自然界的本质属性之一,生物体内许多分子都具有手性。手性化合物在有机化学、生物化学、材料化学等方面有着广泛的应用。不对称有机催化(Enantioselective Organocatalysis)作为二十一世纪新出现的概念,因其高效性和高选择性,成为构建分子骨架的重要工具,在开发手性药物、材料等工业中发挥着巨大的作用,为医药、化学、材料和生物学的发展提供了广阔的应用前景。所以不对称有机催化的实验研究及理论研究具有重要的理论和实际意义。开展不对称有机催化反应的理论研究,从分子水平上研究不对称催化反应的反应机理,可以弄清催化反应的反应历程,解释和说明实验现象,了解有机催化剂在催化反应的过程中所起的作用以及不对称催化反应的立体选择性。本文运用量子化学中的密度泛函理论研究了多立体中心(硫)脲催化剂以及在此基础上发展起来的新型的方酰胺催化剂催化的不对称杂原子迈克尔加成反应,从微观的角度研究不对称催化反应的机理,解释有机催化在催化反应中的作用的本质,从而为研发新型、高效的有机催化剂以及新的不对称有机合成反应提供理论指导。本论文研究的主要内容为:用密度泛函理论(DFT)详细研究了多立体中心氮亚磺酰(硫)脲催化剂催化硝基烯烃与硫代酸的Michael加成反应。计算结果表明,反应有两条路径,路径A生成R构型的产物,路径B生成S构型的产物。决定对映选择性的的步骤是C-S键的生成。两个路径中的决速步骤不同,路径A中r2构型扭转为r2-1为决速步,而在路径B中,质子由叔氨基转移到硝基烯烃的α碳上为决速步骤。计算所得的ee值与实验报道的相符。通过对硝基烯烃与硫代苯甲酸反应的理论计算,我们预测了当用氮亚磺酰(硫)脲为催化剂时此反应具有对映选择性。通过DFT的计算提供了详细的催化反应机制,充分解释了实验现象。这些结果不仅有利于为硫杂Michael加成设计新型的催化剂,还可以为氮亚磺酰(硫)脲催化剂在其他反应中的应用作理论指导。用量子化学中的密度泛函理论研究了新型的方酰胺催化剂催化亚磷酸酯与硝基烯烃的磷杂迈克尔加成反应。从微观角度研究了催化反应的机理和催化剂结构与性能之间的关系。计算结果表明,方酰胺在催化亚磷酸酯和硝基烯烃的反应中并没有起到双活化的功能,只有催化剂中的叔氨基起到质子传递的功能,从而活化了亲核试剂,而催化剂并没有对硝基烯烃进行活化。反应有两条路径,路径A生成R构型的产物,而路径B生成S构型的产物。两个路径中的决速步骤不同,在反应路径A中,第二步质子由叔氨基转移到硝基烯烃的α碳原子上为决速步,而在反应路径B中,C-P键的生成是决速步。虽然路径A和路径B中决速步所需要越过的势垒基本相同,可是由于反应的第一步C-P键的生成,路径A占优势,并且第二步质子的转移过渡态R-TS1的能量比S-TS2的能量要低。所以能判断此催化反应得到的产物中R构型的是优势产物。我们还通过计算催化反应的对映选择性证实了以上观点。计算所得的ee值与实验报道的数值相近。通过DFT的计算提供了详细的催化反应机制,充分解释了实验现象。这些实验结果可以帮我们更好的理解方酰胺催化剂在反应中的作用,并且为方酰胺催化剂的改进和推广提供理论基础。更多还原

【Abstract】 One of the entitative attributes of nature is chirality. Most of molecules in organism are chiral. Chiral compounds are used in organic chemistry, biochemistry and material chemistry widely. Enantioselective organocatalysis as a new concept emerged at the 21st century have been developing into an important tool for constructing of complex molecular skeletons because of its high-efficiency and high selective sensitivity. Enantioselective organocatalysis can offer extensively applied future for medicine, chemistry, material and biology. So, the experimental and theoretical investigations of organocatalytic asymmetric reactions will be of important theoretical and practical values. Theoretical studies of organocatalytic asymmetric reactions not only can understand the reaction mechanism fully from the molecular level but also can explain the experimental phenomenons. It also can make the function of organocatalyst and the origin of enantioselectivity for the catalyzed reaction clear.In this dissertation, we studied the Hetero-Michael reactions catalyzed by multi-stereocentral (thio)urea catalyst and squaramide-catalyst. Theoretical studies by computational methods can explain the reaction mechanism and the essential effect of the catalyst from micromechanism. The results can provide a theoretical direction for developing new type, high effective organocatalysts and novel organocatalytic asymmetric reactions.The valuable results in this dissertation can be summarized as follows:Our DFT calculations provide a first theoretical investigation on enantioselective sulfa-Michael addition reaction of theoacid and trans-β-nitrostyrene catalyzed by N-Sulfinyl urea in CPME solvent. The results show that there are two pathways for the reaction yielding the products. Pathway A which gives (R)-configuration product is favored over the pathway B which yields (S)-configuration product. The enantioselectivity of the sulfa-Michael addition reaction is controlled by the C-S bond-formation step. The rate determining steps are different in two pathways. In pathway A the step of conformational change from r2 to r2-1 is the rate-determining step, which is the proton transfer from the amino group of the catalysts to theα-carbon of the nitrothiolate in pathway B. The ee value we obtain is in agreement with the experimental data. From the calculation of the sulfa-Michael reaction of thiobenzoic acid and trans-β-nitrostyrene which need more sterical demand, we predict that the reaction has enantioselectivity used N-Sulfinyl urea as the catalyst. The present results will stimulate not only the development of novel organocatalyst for sulfa-Michael addition but also the expansion of the scope of N-Sulfinyl urea catalysis.The hetero-Michael reaction of dimethyl phosphate with nitroalkene catalyzed by a squaramide-organocatalyst is investigated using density functional theory (DFT) calculations. The catalysis proceed is by single functional activation. The tertiary amide of the catalyst activates nucleophilic substrate by transformation of proton. However, the electrophilic substrate is not activated.The results show that there are two channels for the reaction between dimethyl phosphate and nitroalkene. Channel A which gives (R)-configuration product is favored over the channel B which yields (S)-configuration product. The rate determining steps are different in two channels. In channel A the step of C-P bond formation is the rate-determining step, which is the proton transfer from the amino group of the catalysts to theα-carbon in channel B. The barriers of the two rate-determining steps are close. But channel A is the favored channel in the first step and in the second step of proton transfer the energy of R-TS1 is lower than that of S-TS1. So (R)-configuration product is preponderant. The enantioselectivity for the reaction is also calculated. The ee value we obtained is in agreement with the experimental fact. The present results will stimulate the expansion of the scope of squaramide catalysis.更多还原