Doctor of Philosophy
Prof. Brian L. Pagenkopf
This dissertation presents two separate chapters within the broad area of synthetic organic chemistry. The first chapter describes the annelation chemistry of donor-acceptor (DA) cyclopropanes and cyclobutanes for the synthesis of heterocycles. The Yb(OTf)3-catalyzed [4+2] cycloaddition between DA cyclobutanes and nitrosoarenes facilitated the synthesis of tetrahydro-1,2-oxazines in good to excellent yields as single diastereomers. Additionally, an unexpected deoxygenation occurred with electron-rich nitrosoarenes under MgI2-catalysis that afforded pyrrolidine products. The GaCl3-catalyzed [4+2] cycloaddition of DA cyclobutanes and cis-diazenes provided hexahydropyridazine derivatives in good to excellent yields as single diastereomers. Furthermore, a procedure to make spiroketals from the [4+2] cycloaddition of spirocyclic DA cyclobutanes and aldehydes is also disclosed. Lastly, a cascade reaction of DA cyclopropanes with nitrosoarenes is discussed. The reaction results in formation of tetrahydro-1,2-oxazine instead of normal cycloadduct isoxazolidine via a tandem ring opening, elimination, and cycloaddition sequence. A detailed discussion of the results along with associated mechanisms is presented.
The second chapter describes multiple strategies applied towards the synthesis of the prodigiosin alkaloid streptorubin B. The key aspect of the strategies is utilization of our group developed [3+2] cycloaddition between DA cyclopropanes and nitriles. An overview of this methodology and its application towards the synthesis of natural products is presented
Vemula, Naresh, "New Chemistry of Donor-Acceptor Cycloalkanes and Studies Towards the Synthesis of Streptorubin B" (2016). Electronic Thesis and Dissertation Repository. 3895.