Chiral Aminophosphines as Catalysts for Enantioselective Double-Michael Indoline Syntheses

The bisphosphine-catalyzed double-Michael addition of dinucleophiles to electron-deficient acetylenes is an efficient process for the synthesis of many nitrogen-containing heterocycles. Because the resulting heterocycles contain at least one stereogenic center, this double-Michael reaction would be even more useful if an asymmetric variant of the reaction were to be developed. Aminophosphines can also facilitate the double-Michael reaction and chiral amines are more readily available in Nature and synthetically; therefore, in this study we prepared several new chiral aminophosphines. When employed in the asymmetric double-Michael reaction between ortho-tosylamidophenyl malonate and 3-butyn-2-one, the chiral aminophosphines produced indolines in excellent yields with moderate asymmetric induction

STUDIES CONCERNING NUCLEOPHILIC PHOSPHINE CATALYSIS AND DESIGNS OF NEW CHIRAL AMINOPHOSPHINES TOWARD ASYMMETRIC PHOSPHINE-CATALYZED REACTIONS

Phosphinocatalysis has been used among us as a short term for nucleophilic phosphine catalysis. The information in chapter 1 will focus on how phosphinocatalysis was discovered, who contributed to the early-day developments of this field, and what have been achieved in the field. Chapter 2 will cover phosphine-allene chemistry in which the equillibrium between phosphonium dienolate and vinylogous ylide was reaffirmed. Two new phosphine-mediated transformations were discovered in this chemistry: vinylogous aldol/P-to-C aryl migration by reaction of phosphonium dienolate with an aromatic aldehyde and vinylogous Wittig olefination by reaction of vinylogous ylide with an aromatic aldehyde. Chapter 3 will discuss the development of a one-pot procedure for phosphine-initiated general base-catalyzed quinoline synthesis and of its variation to quinolone synthesis. A number of 3-substituted and 3,4-disubstituted quinolines, as well as 3-substituted 4-quinolones have been generated from this methodology. Chapter 4 involves the designs of new chiral aminophosphines toward the asymmetric version of phosphine-catalyzed double Michael reaction. The aminophosphines were particularly designed based on the presumption that the anchimeric assistance of the amino group onto the phosphonium phosphorous was essentially significant to the reaction's success. The chiral element was designed to be on the amino group, which would endow the asymmetric environment to the reactive center via anchimeric assistance during the reaction. A small collection of chiral aminophosphines were eventually prepared based on this design. Chapter 5 was an extension on the design of chiral aminophosphines. However, the new design of chiral aminophosphines was not based on any specific asymmetric chemical transformations. This design was centered on the steric-directing mode of asymmetric induction and then would be tested toward various phosphinocatalysis reactions

Parental support to further study in Malaysian public university among male and female secondary school students

The objectives of the study is to identify whether there has a significant difference in parental support to further study in Malaysian public university based on gender, ethnic, and parent’s educational background. The participants involved in this study are form four students from five national secondary schools in Seri Kembangan, Selangor. The total sample size is 347 students (162 males and 185 females). Parental Support to Further Study in Malaysian Public University survey questionnaire was adopted and adapted from FIHSR and FIPHE questionnaires developed by Mundy (n.d.) and Harris (n.d.) respectively to gather data. Kruskal-Wallis Test and Mann-Whitney U Test were used as data analysis techniques in this study. The results revealed a statistically significant difference in parental support to further study in Malaysian public university based on gender, ethnic, and parent’s educational background

One-Pot Phosphine-Catalyzed Syntheses of Quinolines

In this study we developed an efficient one-pot procedure for the preparation of 3-substituted and 3,4-disubstituted quinolines from stable starting materials (activated acetylenes reacting with <i>o</i>-tosylamidobenzaldehydes and <i>o</i>-tosylamidophenones, respectively) under mild conditions. The reaction appears to operate under a general base catalysis mechanism, instigated by the β-phosphonium enoate α-vinyl anion generated in situ through nucleophilic addition of PPh₃ to the activated alkyne. Michael addition of the deprotonated tosylamides to the activated alkynes and subsequent rapid aldol cyclization led to the formation of labile <i>N</i>-tosyldihydroquinoline intermediates. Driven by aromatization, detosylation of the dihydroquinoline intermediates occurred readily in the presence of dilute aqueous HCl to give the final quinoline products

Chiral aminophosphines derived from hydroxyproline and their application in allene–imine [4 + 2] annulation

A robust synthetic route from L-hydroxyproline (L-Hyp) to phosphines has established an expandable library of six chiral aminophosphines, which were then applied to the phosphine-catalyzed [4 + 2] allene-imine annulation. The enantioinduction in the annulations-induced by a purely steric effect-were moderate (up to 57% ee). A switch of the reaction site from the γ- to the β'-carbon atom of the allenoate was observed during the annulations performed using sterically demanding chiral phosphines

Thermoelectric properties of N-type Bi2Te2.7Se0.3 and P-type Bi0.5Sb1.5Te3 films for micro-cooler applications

Bi2Te3 and its solid solution remain the state-of-the-art thermoelectric materials for refrigeration applications in microelectronics industry, such as dissipating the heat generated by various devices. The fabrication method and associated processing parameters are to be optimised to get desirable composition exhibiting better electrical and thermal transport properties. Carrier concentration and mobility are found to be crucial in achieving high thermoelectric cooling efficiency and energy conversion. In this paper, we present the fabrication and analysis of thermoelectric thin films deposited by RF-magnetron sputtering from n-type Bi2Te2.7Se0.3 and p-type Bi0.5Sb1.5Te3 targets on a silicon substrate. X-ray diffraction, Scanning electron microscopy combined with energy dispersive spectrometry, electrical resistivity, Seebeck coefficient and thermal diffusivity measurements were used for the thermoelectric thin films characterization. We studied the effect of sputtering process parameters, on the structural, electrical and thermal transport characteristics of films. The observed results demonstrate both n-and p-type doped Bi2Te3 films exhibit desirable properties and could be potential candidates for thermoelectric micro-cooler applications

Chiral Aminophosphines as Catalysts for Enantioselective Double-Michael Indoline Syntheses

The bisphosphine-catalyzed double-Michael addition of dinucleophiles to electron-deficient acetylenes is an efficient process for the synthesis of many nitrogen-containing heterocycles. Because the resulting heterocycles contain at least one stereogenic center, this double-Michael reaction would be even more useful if an asymmetric variant of the reaction were to be developed. Aminophosphines can also facilitate the double-Michael reaction and chiral amines are more readily available in Nature and synthetically; therefore, in this study we prepared several new chiral aminophosphines. When employed in the asymmetric double-Michael reaction between &lt;em&gt;ortho&lt;/em&gt;-tosylamidophenyl malonate and 3-butyn-2-one, the chiral aminophosphines produced indolines in excellent yields with moderate asymmetric induction