Thesis (Ph. D.)--University of Michigan, 1934. / "By W.E. Bachmann and Helen R. Sternberger." "Reprint from the Journal of the American chemical society, 55 ... (1933); 56 ... (1934)."

Thesis (Ph. D.)--University of Chicago, 1934. / Lithoprinted. "Private edition, distributed by the University of Chicago Libraries, Chicago, Illinois."

Thesis (M. Sc.)--York University, 2001. Graduate Programme in Chemistry. / Typescript. Includes bibliographical references (leaves 85-90). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://wwwlib.umi.com/cr/yorku/fullcit?pMQ71609.

In our previous publication of Thiele cage diols, we describe the first pinacol rearrangement to occur over a C(sp3)–C(sp3). Two mechanisms were initially proposed: a concerted mechanism and a stepwise mechanism, proceeding through a carbocation intermediate. Interestingly, the rearrangement provides only a single diastereomer. The aim of this thesis is to investigate the nature of the reaction by measuring the relative rates of reaction with varying substituents that either stabilize or impede the formation of carbocations. From the relative rates, we can narrow in on whether the mechanism is stepwise or concerted, based on substituent effects, and determine how the reaction may provide a single diastereomer. In Chapter 1, the pinacol rearrangement is introduced, and each analogue that followed after, including stereoselective pinacol rearrangements and a series of different semipinacol rearrangements that provide useful synthetic pathways for chemists with desirable stereochemical outcomes. In Chapter 2, we describe the isolation and characterization of two analogues of a key side product. The structure of each analogue was determined through a series of spectroscopic techniques including 1H-1H COSY, HSQC, HMBC, and 1D-selective gradient NOE NMR. From the solved structures, we proposed a possible mechanism to describe their formation during the main rearrangement reaction – one that shares a carbocation intermediate with the stepwise mechanism already proposed. In Chapter 3, we prepared five Thiele cage diol analogues with aryl substituents with different electronic properties: two substituents that stabilize carbocation intermediates (p-OCH3 and p-CH3), two that destabilize (p-F and 3,5-diOCH3), and the base tetraphenyl Thiele cage diol. We measured the rates of reaction of each diol with p-toluenesulfonic acid at 25°C, 35°C, 45°C, and 52°C via variable temperature quantitative 1H-NMR over time. From the rates of reaction, we found that diols with carbocation-stabilizing aryl substituents reacted faster than the destabilizing analogues, providing evidence that the rearrangement proceeds through a carbocation intermediate. We also found that the diols with electron-deficient aryl substituents showed an increase in the entropy of activation with increasing electron-deficiency in the aryl groups, suggesting an associative pathway for the electron-deficient substituents toward the rearrangement product. Considering the pathway proposed for the side product, we propose an updated stepwise mechanism. Based on computational studies and a previously-isolated X-ray crystal structure, we determined that the diastereoselectivity of the reaction was facilitated by favourable π-π stacking interactions between two aryl substituents. The interaction of the aryl groups twists the geometry of the molecules, placing the migrating aryl substituent in the ideal position for the rearrangement to occur stereoselectively. / Graduate / 2023-10-31

Asymmetric synthesis and catalysis is one of the leading research areas in chemistry society, for its versatility and efficiency in obtaining chiral molecules that found the vast majority in natural active compounds and synthetic drugs. Developing asymmetric catalytic methodology is at the frontier in both industrial and academic research laboratories. Enantioselective organocatalysis has emerged as a powerful synthetic tool that is complementary to metal-catalyzed transformations. The development of chiral phosphoric acid and metal phosphate as catalysts has been a breakthrough in recent years. Chiral phosphoric acids have been shown to be powerful catalysts in many organic transformations. Moreover, chiral metal phosphates, which formed by simply replacing the proton in phosphoric acid with metals, have introduced new catalytic activations and broaden the scope of phosphoric acids. This thesis details new highly enantioselective chiral phosphoric acid-catalyzed Pinacol rearrangement and robust alkaline phosphates catalytic system, which utilizes novel carbonyl activation. The Pinacol rearrangement has long been known to be difficult to control in terms of regioselectivity and stereoselectivity. The initial studies found that indolyl-diol compounds can be treated with chiral phosphoric acids to afford the Pinacol rearrangement with high regio- and enantioselectivity. Over 16 chiral phosphoric acids were screened, and it was found an H8-BINOL-phosphoric acid variant with 1-naphthyl groups at 3 and 3' position was the excellent catalyst. This asymmetric transformation is tolerant toward variety of substituents both on the indole ring and migrating groups. During the study, it was found that different ways to generate the catalyst had critical effect on this catalytic transformation. Only those phosphoric acids washed with HCl after column chromatography afforded the rearrangement products with high enantioselectivity. And those without treating with HCl were found contaminated by alkaline metals. These "contamination" catalysts were also found active with carbonyl activations. A highly enantioselective catalytic hetero-Diels-Alder reaction of alpha-keto esters has been developed with chiral alkaline metal phosphates. A calcium 1-naphthyl-BINOL phosphate was found to be the optimum catalyst. A large range of alpha-keto esters as well as isatins can be applied in this alkaline phosphates catalytic system with high efficiency and selectivity. The structure of the catalyst is detailed for the first time by X-ray crystal structure analysis. A proposed Transition state model is provided based on the catalyst crystal structure and Raman spectroscopy analysis. This methodology was further developed with an asymmetric Mukaiyama-Michael addition of beta,gamma-unsaturated alpha-keto ester. The best catalyst was found to be a magnesium chiral phosphate. And the transformation was found capable of tolerating a wide variety of beta,gamma-unsaturated alpha-keto esters.