A general synthesis of highly substituted 2-naphthols based on a new carbanionic reaction sequence is demonstrated. The reaction exploits the dual nature of lithium bases consisting of consecutive ring opening of readily available coumarins with either LiNEt or LiNiPr into Z-cinnamamides, thus generating a directing group in situ and allowing, by conformational freedom, a lateral directed remote metalation for ring closure to give the aryl 2-naphthols in good to excellent yields. These transformations can be combined to provide a more efficient one-pot process. Mechanistic insight into the remote lateral metalation step, demonstrating the requirement of Z-cinnamamide, is described. Application of this methodology to the synthesis of highly substituted 3,3'-diaryl BINOL ligands is also reported.
A general synthesis of highly substituted 2‐naphthols based on a new carbanionic reaction sequence is demonstrated. The reaction exploits the dual nature of lithium bases consisting of consecutive ring opening of readily available coumarins with either LiNEt2 or LiNiPr2 into Z‐cinnamamides, thus generating a directing group in situ and allowing, by conformational freedom, a lateral directed remote metalation for ring closure to give the aryl 2‐naphthols in good to excellent yields. These transformations can be combined to provide a more efficient one‐pot process. Mechanistic insight into the remote lateral metalation step, demonstrating the requirement of Z‐cinnamamide, is described. Application of this methodology to the synthesis of highly substituted 3,3′‐diaryl BINOL ligands is also reported.
Based on the fundamental theory of electrochemical anodic polarization, simulated concrete is doped with corrosion inhibitor to prevent corrosion by chloride ion in the marine environment. Thus, with reference to the potential-time curves obtained in different concrete environments and construction conditions, the early dynamic state of active transition of rebar passive films in concretes can be quickly characterized. According to the experiments, the characteristics of passive active transition are synchronous with rebar corrosion. This helps to systematically study the influence of different components of concrete and external media on the durability of the concrete structure. The strong alkaline environment of the concrete is useful in controlling corrosion rate of reinforcing bar. As one of the additional protective measures of the durability of the concrete structure, corrosion inhibitor’s long-term performance contains uncertainty.
Concrete structure is widely used in civil engineering. Concrete cracking, a common and frequently occurring disease, is one of the main factors that cause impaired concrete structure durability. This paper analyzes the generation process and features of non-longitudinal concrete cracking. With on-site investigation of selected buildings in Ningbo, the paper discusses the main existing non-longitudinal cracks and their impact on the durability of concrete structure.
The detection index and evaluation for foundation engineering’s corrosion are performed in accordance with the “Code for Highway Engineering Geological Investigation” or “Code for Investigation of Geotechnical Engineering”. For both steel pipe piles and concrete pipe pile joints, the codes don’t consider the dissolved oxygen, Anaerobic organism and other corrosion factors. In order to improve the durability of the pipe pile foundation in coastal region, taking the typical coastal soft soil characteristics in eastern Zhejiang as example and by observing the steel corrosion electrochemical potential variation in the hypoxic environment, this paper analyses the corrosion risk of steel structures in marine deposit soft soil, and puts forward the microbial and electrochemical corrosion mechanism of the steel structures in foundation engineering in coastal environment. This paper argues that the Sulfate-Reducing Bacteria corrosion evaluation is indispensable in geotechnical investigation, and therefore should be included into the Code.
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