Catalyst development towards asymmetric synthesis

The description of a systematic study to quantify the chemoselectivity differences between the various classes of carbenoids and demonstrate that donor-acceptor diazo compounds are considerably more chemoselective than any system previously studied in the literature will take place. This will include a brief background on the α-diazocarbonyl compounds and the formation of metal stabilized carbenes, or carbenoids. This will be followed by previous work in cyclopropanation chemistry with an emphasis on the chemoselectivity, as well as, the chemoselectivity of ethyl diazoacetate and its derivatives. This will be followed by a description of the Hammett equation and the mechanistic knowledge that can be obtained from Hammett studies. This will be followed by a description of the cyclopropanation chemistry of carbenoids derived from donor-acceptor stabilized diazo compounds, which will focus on the chemoselectivity differences. Finally, a systematic study on the chemoselectivity of the various carbenoids will be described.; This will be followed by the synthesis of a new class of conformationally restricted rhodium(II) catalysts and demonstrate through the testing of these catalysts that they support the previously established model for the asymmetric induction of rhodium(II) tetraprolinates. With a brief background on dimeric rhodium(II) catalysts and the catalytic cycle for the cyclopropanation of alkenes with diazo compounds, followed by previous work in cyclopropanation chemistry with an emphasis on the diastereoselectivity, and a description of rhodium carboxylate catalysts and focus on the Davies chemistry, cyclopropanations of alkenes by donor/acceptor substituted diazo compounds in the presence of rhodium(II) tetraprolinate catalysts. This will be followed by a description of the postulated model for the asymmetric induction of Rh₂( S-DOSP)₄ (33) and Rh₂( S-TBSP)₄ (68) catalysts. Finally, the total synthesis of a new class of rigid D₂ symmetric catalysts will be described followed by the implementation of these catalysts in various cyclopropanation test reactions. The results from the various catalysts will give insight into what is needed for optimal asymmetric induction.; This will be followed by the testing of this new class of rigid D ₂ symmetric catalysts in aziridination reactions with nitrenes. A comparison of cyclopropanation and aziridination will take place.