CBS还原合成手性1-苯乙醇实验设计*

将学科热点之一催化不对称合成策略引入实验教学中,通过CBS还原制备手性醇。实验以苯乙酮为原料,还原得到粗产物手性1-苯乙醇,经制备色谱仪分离提纯,气相色谱和自动旋光仪表征产物的光学性质。实验为综合型有机化学实验,通过此实验,学生在掌握手性醇合成原理与方法的同时,进一步学习手套箱、气相色谱、制备色谱仪、自动旋光仪等新技术,以提升学生综合科研素质。     

L-脯氨酸催化的不对称Aldol缩合反应实验设计

介绍了L-脯氨酸催化的对硝基苯甲醛与丙酮的不对称Aldol反应的实验设计。室温反应2 h后，柱层析得到（R）-4-（4-硝基苯基）-4-羟基-2-丁酮，利用手性高效液相色谱测试得到产物的ee值。学生实验结果显示，收率范围为53%~74%，对映选择性范围为62%~69%。本实验方案将Aldol反应的研究成果设计成综合性实验，不仅强化训练了学生基本的实验技能和操作，同时拓宽了知识面，培养了学生分析问题、解决问题等方面的综合能力。     

用硼酸作催化剂一锅法合成双（二氢化嘧啶酮-4-基）苯

A simple effective synthesis of bis(dihydropyrimidinone-4-yl)benzene derivatives, using boric acid as catalyst,from isophthalic aldehyde or terephthalic aldehyde, 1,3-dicarbonyl compounds and urea or thiourea in glacial acetic acid was described. As the expansion of the classical Biginelli reaction, this method has the advantage of excellent yields 83%-94% and short reaction time 0.5-1.5 h.     

Cold atom clocks and their applications in precision measurements

Cold atom clocks have made remarkable progresses in the last two decades and played critical roles in precision measurements. Primary Cs fountain frequency standards have achieved a total uncertainty of a few parts in 1016, and the best optical clock has reached a type B uncertainty below 10-18. Besides applications in the metrology, navigation, etc.,ultra-stable and ultra-accurate atomic clocks have also become powerful tools in the basic scientific investigations. In this paper, we focus on the recent developments in the high-performance cold atomic clocks which can be used as frequency standards to calibrate atomic time scales. The basic principles, performances, and limitations of fountain clocks and optical clocks based on signal trapped ion or neutral atoms are summarized. Their applications in metrology and other areas are briefly introduced.     

5-芳亚甲基海因的微波合成和晶体结构

用芳醛、海因为原料在微波辐射下合成了一系列的5-芳亚甲基海因，产物的结构经红外、核磁共振、单晶X射线衍射分析表征．     

Dialdehyde in Heterocyclic Synthesis： Synthesis of Compounds Containing Two 4H-Benzopyran Building Blocks under Microwave Irradiation

The syntheses of 4H-benzopyran derivatives were investigated using dialdehyde as a key starting material. The reaction proceeds under microwave irradiation in good yield (87%--95%) with short reaction time (5--8 min),therefore providing a rapid and efficient method of synthesizing a variety of compounds containing two 4H-benzopyran units.     

微波辐射下无溶剂合成4－芳基－5－乙氧羰基－6－甲基-3，4－二氢吡啶－2－酮

以芳醛、乙酰乙酸乙酯、麦氏酸和醋酸铵为原料，在无溶剂条件下用微波辐射 后合成了一系列4－芳基－5－乙氧羰基－6－甲基－3，4－二氧吡啶－2－酮。     

微波辐射下"一锅煮"法合成2-氨基-3-氰基-4-芳基-4H,5H-吡喃-[3,2-c]苯并吡喃-5-酮

以芳醛、4-羟基香豆素、丙二腈为原料,乙醇为能量转移剂,哌啶为催化剂,在微波辐射下一步合成了一系列2-氨基-3-氰基-4-芳基-4H,5H-吡喃-[3,2-c]苯并吡喃-5-酮,反应在40～60s时间内完成,产率60%～97%.     

Accurate Evaluation of Microwave-Leakage-Induced Frequency Shifts in Fountain Clocks

We report theoretical calculations of the transition probability errors introduced by microwave leakage in Cs fountain clocks, which will shift the clock frequency. The results show that the transition probability errors are affected by the Ramsey pulse amplitude, the relative phase between the Ramsey field and the leakage field, and the asymmetry of the leakage fields for the upward and downward passages. This effect is quite different for the leakage fields presenting below the Ramsey cavity and above the Ramsey cavity. The leakage-field-induced frequency shifts of the NIM5 fountain clock in different cases are measured. The results are consistent with the theoretical calculations, and give an accurate evaluation of the leakage-field-induced frequency shifts, as distinguished from other microwave-power-related effects for the first time.     

5-对甲氧基苯亚甲基咪唑啉-2,4-二酮的微波合成和晶体结构

标题化合物C11H10N2O3是由咪唑啉-2,4-二酮、对甲氧基苯甲醛在微波辐射下反应而得, 反应在5分钟内完成。结构通过单晶X-射线衍射法测定,其晶体属三斜晶系,空间群P, Mr = 218.21, a = 5.346(1), b = 10.212(2), c = 10.368(2) ? ?= 72.34(2), ?= 75.35(2), ?= 78.09(2), V = 516.6(2) ?, Z = 2, Dc = 1.403 g/cm3, = 0.104 mm-1, F(000) = 228, R = 0.0442, wR = 0.1152。咪唑环与苯环之间的两面角为5.45, 分子之间存在氢键, 形成了网状结构。