Asymmetric Total Synthesis of (+)-Nominine: Development of a Dual Cycloaddition Strategy for the Synthesis of the Hetisine Alkaloids

313 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2007.A dual cycloaddition strategy for the synthesis of the hetisine alkaloids has been developed and applied to the asymmetric total synthesis of nominine. The approach relies on an early stage intramolecular aza-1,3-dipolar cycloaddition of a 4-oxidoisoquinolinium betaine with an ene-nitrile dipolarophile and a late stage intramolecular [4+2] Diels-Alder cycloaddition. Also of note is the development of a new method for the preparation of 4-oxidoisoquinolinium betaines. Overall, a 16 step asymmetric synthesis of (+)-nominine was accomplished in 1.3% yield, while (+/-)-nominine was prepared in 15 steps in 6.1% yield.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD

Asymmetric Total Synthesis of (+)-Nominine: Development of a Dual Cycloaddition Strategy for the Synthesis of the Hetisine Alkaloids

313 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2007.A dual cycloaddition strategy for the synthesis of the hetisine alkaloids has been developed and applied to the asymmetric total synthesis of nominine. The approach relies on an early stage intramolecular aza-1,3-dipolar cycloaddition of a 4-oxidoisoquinolinium betaine with an ene-nitrile dipolarophile and a late stage intramolecular [4+2] Diels-Alder cycloaddition. Also of note is the development of a new method for the preparation of 4-oxidoisoquinolinium betaines. Overall, a 16 step asymmetric synthesis of (+)-nominine was accomplished in 1.3% yield, while (+/-)-nominine was prepared in 15 steps in 6.1% yield.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD

General Method for the Preparation of Electron-Deficient Imidazo[1,2‑<i>a</i>]pyridines and Related Heterocycles

A new annulation method for the preparation of the imidazo­[1,2-<i>a</i>]­pyridine ring system under mild conditions is presented. Treatment of a 2-aminopyridine with a dimethylketal tosylate in acetonitrile at elevated temperature (80–140 °C) in the presence of catalytic Sc­(OTf)₃ provides the imidazo­[1,2-<i>a</i>]­pyridine product in good yield. The annulation method is broadly applicable to electron-poor 2-aminopyridines and displays a complementary profile to the classic preparation of the imidazo­[1,2-<i>a</i>]­pyridine ring system by reaction of a bromoketone with electron-rich and -neutral substrates. The scope of the process and mechanistic considerations are discussed

Spatial and Temporal Patterns of Benthic Invertebrate Communities in the Susquehanna River Revealed Using Data From 20 Years of Surveys by Multiple Agencies

State and federal agencies frequently conduct benthic macroinvertebrate surveys for bioassessment across large spatiotemporal scales. However, these data are rarely used outside speci?c regulatory agencies to address ecological questions. To account for

Tandem Ring-Closing Metathesis/Transfer Hydrogenation: Practical Chemoselective Hydrogenation of Alkenes

An operationally simple chemoselective transfer hydrogenation of alkenes using ruthenium metathesis catalysts is presented. Of great practicality, the transfer hydrogenation reagents can be added directly to a metathesis reaction and effect hydrogenation of the product alkene in a single pot at ambient temperature without the need to seal the vessel to prevent hydrogen gas escape. The reduction is applicable to a range of alkenes and can be performed in the presence of aryl halides and benzyl groups, a notable weakness of Pd-catalyzed hydrogenations. Scope and mechanistic considerations are presented