Abstract Optically active amines represent critically important subunits in bioactive natural products and pharmaceuticals, as well as key scaffolds in chiral catalysts and ligands. Kinetic resolution of racemic amines and enantioselective desymmetrization of prochiral amines have proved to be efficient methods to access enantioenriched amines, especially when the racemic or prochiral amines were easy to prepare while the chiral ones are difficult to be accessed directly. In this Account, we systematically summarized the development of kinetic resolution and desymmetrization of amines through nonenzymatic asymmetric catalytic approaches in the last two decades. 1 Introduction 2 Kinetic Resolution of Amines 2.1 Kinetic Resolution of Amines via Asymmetric Transformations of the Amino Group 2.1.1 Asymmetric N-Acylations 2.1.2 Asymmetric N-Alkylation 2.1.3 Asymmetric N-Arylation 2.1.4 Other Asymmetric N-Functionalizations 2.1.5 Asymmetric Dehydrogenation of Amines 2.1.6 Selective C–N Bond Cleavage of Amines 2.2 Kinetic Resolution of Amines via Asymmetric Transformations without Amino Group Participating 3 Enantioselective Desymmetrization of Amines 3.1 Desymmetrization of Diamines 3.2 Desymmetrization of Prochiral Monoamines 4 Conclusion and Outlooks
Many modeling methods were discussed,which included uniaxial strain model,tectonic stress model/strain boundary model and plane strain model.Plane strain model for comprehensive evaluation of mining machinery was quite accurate in practical applications.Layering earth stress and mechanic parameters of Well Shang X in Jiyang Depression are calculated.By optimization technology of layering earth stress and mechanic parameters,the comprehensive measure can control the creation of the harmful crack.
The traditional underbalanced drilling technology cannot solve the problems of the low penetration rate and simple reservoir protecting measures in the west Sichuan interval of more than 3000 m. The Southwest Subsidiary Company introduces nitrogen drilling technology to better protect and discover hydrocarbon reservoirs and advance the success rate of deep well exploring. Based on large amounts of geological and engineering appraisal, application test of nitrogen drilling technology is conducted in the producing interval of 4652.26～4775.56 m during the fourth spudding in DY1 well. The test shows that the application of the new technology has brought good effect and greatly increased the drilling speed. The average rate of penetration of the interval reaches as high as 8.36 m/h, 8~9 times higher than that of the offset well, meanwhile, a fractured gas reservoir is discovered. The successful application of the new technology in exploring deep wells accelerates the popularization of the gas drilling technology and can be a good reference for drilling in similar regions.
The development process of 12V240ZJ diesel engines was briefly presented. The comparisons of two types of assorted supercharging schemes used in the design and development were mainly explained. The performance test results of this diesel engine were analyzed and summarized. The work to be done to further increase diesel engine power and improve performance indices was pointed out.
An ascorbic acid-promoted and metal-free tandem room temperature cyclization of N-arylacrylamides with 4-nitrobenzenediazonium generated in situ was developed. This reaction proceeds smoothly through a radical mechanism and provides an environmentally friendly alternative approach to biologically active 3-alkyl-3-benzyloxindoles, avoiding the use of excess oxidants and light irradiation.
This chapter contains sections titled: Introduction Geological Characteristics in Taizhou Formation of Caoshe Oil Field Techniques to Improve the Effect of CO2 Flooding Selecting and Evaluating of Surfactant Conclusions
Cyanuric chloride was used as raw material to synthesize two new bifunctional light stabilizers which contain hindered amine structure——2-phenyl-4,6-bis[2-hydroxyl-4-(2,2,6,6-tetramethylpiperidine-4-yloxycarbonylmethoxy)phenyl]-1,3,5-triazine(Ⅳa)and 2-phenyl-4,6-bis[2-hydroxyl-4-(1,2,2,6,6-pentamethylpiperidine-4-yloxycarbonylmethoxy)phenyl]-1,3,5-triazine(Ⅳb) via Grignard reaction,Friedel-Craft reaction,etherification reaction and transesterification reaction.The yields of Ⅳa and Ⅳb are 37.6% and 38.1% respectively.The structures of the target compounds were characterized by means of FTIR,MS and 1HNMR.Ultraviolet absorption performance of the target compounds was tested.The results show that the target compounds have strong absorption in 270~400 nm.The maximum molar absorption coefficient(emax) of compounds Ⅳa and Ⅳb respectively was 6.651 3×104(276 nm),2.837 4×104(339 nm)L·mol-1· cm-1 and 6.435 9×104(276 nm),2.648 3×104(339 nm)L·mol-1· cm-1.
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