Site‐selectivity, differentiating members of the same functional group type on one substrate, is an emerging tactic for shortened advanced building block and biomolecule synthesis. Despite its potential, site‐selectivity remains less studied and especially so for ketone‐based substrates. During this work ketone site‐selectivity has been coupled with the chiral amine‐catalyzed aldol desymmetrization of 4‐keto‐substituted cyclohexanones, allowing three stereogenic centers to form in the aldol product while leaving the acyclic ketone unreacted. Unique here, compared to all previous 4‐substituted cyclohexanone desymmetrizations, is the first access to synthetically useful quantities of an epimeric (remote stereogenic center) aldol product. To demonstrate the value of these aldol products, we show their elaboration into eight keto‐acetonide and one keto‐lactone products. All compounds were isolated as single diastereomers and in high ee (≥96%). These efforts represent the first full characterization of aldol products with type III, Figure 2, relative stereochemistry, regardless of the enantiomer formed.
This paper concentrates on the issues with the aim of providing a constant dc‐link voltage and desired power sharing for a distributed energy storage system (DESS)‐based hybrid microgrid under load variations. The hybrid microgrid which is consisted of PV system, lithium battery‐based storage system and a grid‐connected dc/ac converter are controlled by designing a controller based on the zero dynamics‐based mathematical equations of all used converters. Two buck and bidirectional buck‐boost dc/dc converters employed in PV and DESS systems, respectively, are responsible for damping the dc‐link voltage fluctuations, and also the grid‐connected converter is set to enhance the grid power quality and supply continuously the grid‐connected loads. The main contributions of the proposed control technique are simplicity and providing the simultaneous stable performance for both DC and AC sides under both DC and grid‐connected loads variations. Moreover, another contribution of the proposed control technique is providing accurate coordination in both steady‐state and dynamic conditions. To analyze the proposed controller, the dynamic operations of the converters in various operating conditions are evaluated. In this evaluation, several curves based on their zero dynamics are achieved, and their desired operations are completely investigated in different operating conditions. Simulation results in MATLAB/SIMULINK verify the proposed controller ability at reaching the desired zero dynamics and the stable performance of the proposed hybrid microgrid. 相似文献
