Synthesis and Study of Silylpyrrolidines, Pyrrolidinylsilanols and Silanediols as New Organocatalysts
Author | : Taewoo Min |
Publisher | : |
Total Pages | : |
Release | : 2012 |
ISBN-10 | : 1267759690 |
ISBN-13 | : 9781267759696 |
Rating | : 4/5 (90 Downloads) |
Book excerpt: Chapter 0 (Introduction): This chapter introduces the basic concepts of organocatalysts and importance of hydrogen-bonding interactions. This chapter also describes the reasoning of why we are interested in silicon-containing organocatalysts. Chapter 1: Several silyl pyrrolidine catalysts are synthesized demonstrating the importance of chiral addition with silyl fluoride electrophiles in high yields and enantioselectivity. This new class of silyl pyrrolidines catalysts promotes asymmetric Michael reactions with 5 mol % catalyst loading and afford up to 96% yield and 99% ee with various aldehydes and nitroolefins. ESI-MS spectrometry is used to better understand the mechanism of the Michael reactions involving silyl pyrrolidines, which also contributes new insight that is applicable to other pyrrolidine catalysts. Chapter 2: Silanol functional groups are incorporated onto a pyrrolidinyl scaffold with high enantioselectivity to investigate the catalytic activity of a new bifunctional catalyst. The hydrogen-bonding properties of silanols are investigated using NMR spectroscopy binding studies and ESI-MS analysis. Pyrrolidinylsilanol catalysts afford up to 82% yield and 88% ee in asymmetric aldol reactions between isatin and acetaldehyde. Chapter 3: The design and synthesis of new chiral functionalized silanediol scaffolds is described with the goal to understand the stability of silanediols and prevent condensation. The hydrogen-bonding properties of these new silanediols are studied using NMR spectroscopy binding studies. Chapter 4: New achiral silanediols scaffolds are synthesized to study the steric and electronic effects for stability, acidity, and catalytic activity. The hydrogen-bonding properties of silanediols are studied using X-ray structure analysis, NMR spectroscopy binding studies with Lewis bases, and IR spectroscopic analysis. The first example of catalysis with a silanediol is demonstrated in Diels-Alder reactions and provides insight to design a new class of organocatalysts containing the silanediol functional group.