Jae-Young Lee

CATALYTIC ASYMMETRIC ALLENYLATION : REGULATION OF THE EQUILIBRIUM BETWEEN PROPARGYL- AND ALLENYLSTANNANES DURING THE CATALYTIC PROCESS

Achiral substrates 1 and 2 can be regioselectively converted into chiral allenyl alcohols 3 through the title reaction [Eq. (1)] with the synergetic reagent iPrSBEt2 and a chiral TiIV catalyst. The dramatic regioselectivity originates from the regulation of the equilibrium between propargyl- and allenylstannanes during the catalytic process.

Catalytic asymmetric allylic transfer reaction: (4-trimethylsilylbut-2-ynyl)stannane as a new reagent leading to the enantioselective synthesis of dienyl alcohols

Catalytic enantioselective addition of (4-trimethylsilylbut-2-ynyl)tributylstannane to aldehydes provides trimethylsilylmethylallenyl alcohols in high enantioselectivity which can be converted with a second electrophile to the corresponding dienyl alcohols.

Adaptive line code selection by identification efficiency for RFID systems

RFID passive tags transmit their information by reflecting a readers continuous wave. The strength of the reflected signal by a tag is very weak. So the signal of tags may be easily corrupted by noise or interference. In EPCglobal Class1 Generation2, four types of line codes are presented to adapt to varying channel conditions. However what type of line code is used is not specified in the EPCglobal Class1 Generation2 specification. In this paper, we propose a new line code selection algorithm which estimates the efficiency of the line codes reflecting the channel status and adaptively changes the line code at each frame. We show that the identification performance is enhanced by using our line code selection algorithm via analysis and simulation.

Internal Flow Analysis on a Mixed Flow Pump for Developing Marine Mineral Resources

The development of lifting pumps that lift minerals to a mining vessel are one of the vital parts of the commercial mining process. The purpose of this study is to investigate internal flow and its effect on the performance of a mixed flow pump in order to improve the pump`s performance. Numerical analysis was performed by commercial code of ANSYS CFX-11 based on flow rate and length of flexible hose. The rated rotational speed of the impeller is 1750rpm. For taking into account the turbulence, k- SST model was selected to guarantee more accurate prediction of flow separation. The simulated results are in good agreement with the experimental results and showed that its efficiency and the head of the pump are related mainly to the flow rate and the length of flexible hose. A lesser flow rate caused more secondary flow through the guide vane passage. The length of flexible hose and flow rate exert much more influence on the pump`s performance than the shape of the flexible hose.

Asymmetric routes in the reaction of cyclic ketene ortho ester with aldehydes involving the use of chiral Lewis acid

Enantio- and diastereoselective synthesis of threo 2 and erythro 3 was accomplished by the conversion of 1 with aldehydes promoted by chiral borane 10; enantioselctivities range from 45–95% ee, while diastereoselectivities vary from 4.3–49∶1 with 8 different aldehydes.

Regulation of diastereoselectivity through the epimerisation of a cyclic intermediate in the reaction of cyclic ketene ortho ester with aldehydes

A highly stereocontrolled synthesis of 3 was accomplished. This involves the conversion of the cyclic intermediate 5 (from the reaction of dihydropyran 1 with aldehyde promoted by Lewis acid catalyst) to 6 in the presence of bases and introduction of an ester functionality from hydrolysis of the ortho ester intermediate. The method described herein is successful with a variety of aldehydes and affords products in high yields (55–89%) with useful levels of diastereoselectivity (10–30∶1). Experiments are described which unambiguously established the stereochemistry for the coupling products. Synthetic manipulations of products by functional group transformations to useful compounds are also reported.