Date of Award
2008
Degree Type
Dissertation
Degree Name
Doctor of Philosophy in Chemistry
Abstract
L-methyl prolinate and various α,β-unsaturated ketones were reacted by a tandem sequence of conjugate addition and subsequent autocatalytic intramolecular cyclization to yield 1,3-dicarbonyl-pyrrolizidine ring systems in modest yield. This methodology represents a tandem and green preparative reaction sequence where L-proline is self-generated as an organocatalyst subsequent to the first step and prior to the second step of the process. This sequence of reactions is a one-pot, tandem, and green preparative reaction for the synthesis of various pyrrolizidine derivatives which can be performed in a general and simple way under solventless and room temperature conditions. This methodology is modest yielding and environmentally friendly, factors that represent relevant advantages from a synthetic point of view. Additionally, the catalyst utilized for the reaction has the advantage of being chiral, readily available, inexpensive, non-toxic, and easily removed. The reaction is partially diastereoselective which contributes to the remarkable advantages for this synthetic methodology. β-monosubstituted enones react in a tandem sequence of conjugate addition - cyclization whereas β-disubstituted enones react by a homodimerization process. The cyclization reaction is only partially accomplished for α-substituted unsaturated enones. The hindrance provided by the group in the α-position determines the extent of completion of the cyclization reaction to afford the final product.
Recommended Citation
Sandoval, Sergio, "Tandem conjugate addition -- Cyclization reactions of L-methyl prolinate with α,β-unsaturated ketones catalyzed by L-proline" (2008). Open Access Dissertations. Paper 2233.
https://digitalcommons.uri.edu/oa_diss/2233
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