17 research outputs found
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Oh, Where Electrons Will Go
This dissertation involves the study and manipulation of molecular orbitals on ambiphilic molecules to obtain unusual properties and develop new applications. Carbenes, which can simultaneously serve as powerful Brønsted bases and Lewis acids, undergo further amplification of those properties as the bond angle at the carbene center changes (chapter 2). Such profound reactivity fluctuations from seemingly simple geometric modifications highlight the need for accurate measurement of carbene frontier orbitals. However, X-ray and NMR studies show that carbene-selenium adducts are susceptible to H-Se non-classical hydrogen bonds which cause large downfield shifts in 77Se NMR, disrupting a commonly used technique for assessing carbene π-acidity (chapter 3). Furthermore, common techniques used to characterize carbene donor abilities are unable to avoid the confounding of carbene basic and acidic orbitals. To directly see how carbene lone pairs compare to each other, we ranked different carbene families by basicity through a proton exchange method (chapter 4). The basicity ranking highlights several surprising qualitative errors that occur throughout many theoretical calculations. Finally, exploring the reactivity of aminoboranes, a class of 1,2-ambiphiles, we developed a new methodology for the synthesis of aldimines (chapter 5). Preliminary mechanistic studies suggest that the mechanism is orthogonal to traditional condensation methods and allows access to products that are conventionally difficult to obtain. This dissertation will hopefully serve as another example of how we can advance main-group synthetic chemistry by taking a molecular orbital perspective
Data from: The influence of C(sp3)H-Selenium Interactions on the 77Se NMR Quantification of the π-Accepting Properties of Carbenes
The Influence of C(sp<sup>3</sup> )H-Selenium Interactions on the <sup>77</sup> Se NMR Quantification of the π-Accepting Properties of Carbenes.
The Influence of C(sp <sup>3</sup> )H–Selenium Interactions on the <sup>77</sup> Se NMR Quantification of the π‐Accepting Properties of Carbenes
Readily Available Primary Aminoboranes as Powerful Reagents for Aldimine Synthesis
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The Influence of C(sp 3 )H–Selenium Interactions on the 77 Se NMR Quantification of the π‐Accepting Properties of Carbenes
Selenium NMR has become a standard tool for scaling the π-accepting character of carbenes. Herein, we highlight that non-classical hydrogen bonding (NCHB), likely resulting from hyperconjugation, can play a significant role in the carbene-selenium 77 Se NMR chemical shift, thus triggering a non-linear behavior of the Se-Scale
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The Influence of C(sp 3 )H–Selenium Interactions on the 77 Se NMR Quantification of the π‐Accepting Properties of Carbenes
Cyclic(Alkyl)(Amino)Carbene Ligands Enable Cu-Catalyzed Markovnikov Protoboration and Protosilylation of Terminal Alkynes: A Versatile Portal to Functionalized Alkenes
Regioselective hydrofunctionalization of alkynes represents a straightforward route to access alkenyl boronate and silane building blocks. In previously reported catalytic systems, high selectivity is achieved with a limited scope of substrates and/or reagents, with general solutions lacking. Herein, we describe a selective copper-catalyzed Markovnikov hydrofunctionalization of terminal alkynes that is facilitated by strongly donating cyclic (alkyl)(amino)carbene (CAAC) ligands. Using this method, both alkyl- and aryl-substituted alkynes are coupled with a variety of boryl and silyl reagents with high α-selectivity. The reaction is scalable, and the products are versatile intermediates that can participate in various downstream transformations. Preliminary mechanistic experiments shed light on the role of CAAC ligands in this process