Presentation on theme: "Effects of Varying Acidic Conditions on Ring Closure of acyliminium Ion Intermediates in the Synthesis of Aryl- substituted bicyclic lactams: Finding."— Presentation transcript:
Effects of Varying Acidic Conditions on Ring Closure of acyliminium Ion Intermediates in the Synthesis of Aryl- substituted bicyclic lactams: Finding Optimal Conditions for Increasing Yields. Teresa Phan Dr. Buonora California State University, Long Beach
Introduction Bicyclic Lactams Making Bicyclic Lactam Experiment: Varying pH on Ring Closure Anticipated Results Concluding Remarks
Libraries of dihydropyridazinones and hydroxamic acids as potential pharmaceutical uses and advancement in organic synthesis Ex: inodilators and phosphodiesterase inhibitors Find conditions to optimize yields of each reaction to increase efficiency Bicyclic Lactams are important starting materials
Vehicles for the construction of natural and unnatural products containing quaternary carbon centers 1-aza-8-oxo-4-oxa-[3.3.0]bicyclooctanes These α-hydrogens can be replaced and more functional groups added
Bicyclic lactams from cyclodehydration of amino alcohols and dicarbonyl compounds One synthetic step, limited only by availability of ketoacid Limitation on the angular position
~ Cyclic Anhydride and Amino Alcohol Yields an Imide ~ In this case, succinic anhydride and ethanolamine where heated to form ethanol succinimide.
~ Imide and Grignard (or Hydride) Yields Carbinolamine, Which Under Acidic Conditions Results in Ring Closure to Form Bicyclic Lactams ~ In this case, the ethanol succinimide was reacted with two molar equivalences of an aryl-substituted Grignard Reagent and then refluxed overnight with an acid catalyst.
Grignard reagents can add a greater variety of R groups at the angular position Better yields than the respective cyclodehydration route Previous studies indicate that reagent stoichiometry and solution pH during ring closure may directly affect yields (2-step synthesis involving N-acyliminium species)
Uses Grignard Reagents: RMgBr Grignard Reagents are Very Reactive Nucleophiles Concentration Deteriorate With Time, Moisture and Air True Concentrations Found by Direct Titration Using sec-Butanol in Xylene and 1,10-Phenanthroline as Indicator Grignard Reagents Should be Titrated Once a Month
LG Remove water as it forms to push reaction forward Azeotropic removal of water with Dean-Stark Trap Minimum-boiling azeotropes: azeotrope comes off the liquid first Heptane instead of toluene
Run TLC, visualize with vanillin solution Push through silica gel plug Radial Chromatography (Chromatotron) Collect Fractions in Tubes Run TLC to Combine Tubes Evaporate off Solvent Via Rotary Evaporator Analyze by NMR Find Percent Yield by Weight of Purified Product
1H NMR of Phenyl-substituted Bicyclic Lactam Compound and purity were identified by NMR spectra. Also by IR, C-13 NMR, and TLC spotting.
Vary the pH upon ring closure of Bicyclic lactams. Yes No Correlation between yields and pH? There is an optimal pH. Ring closure is not affected by pH. Vary reagent stoichiometry. Use the optimal pH and vary reagent stoichiometry.
List acidic buffers of different strengths and pH Record the yields Find a relationship between acidic conditions and yields
There would be an optimal pH. Closer to pH of 6 or near 7. Very Strong acids will cause unwanted chemistry If there is a correlation between pH and ring closure:
We will find out if pH affects the yields by looking for peaked yields at a specific pH It may be that the pH does not matter as much as the type of acid used If we can’t get yields to increase to >90%, then we have to look at reaction preferences as well as reagent stoichiometry
Vary the reagent stoichiometry Vary the R groups on the angular position: Aromatic vs. Allyl Alkyl: Straight Chain vs. Branched
Industrial Size Distillation Column Future Applications: Dihydropyridazinone and Hydroxamic Acid derivatives Dihydropyridazinone and Hydroxamic Acid derivatives Medicine Medicine Safer Insecticides Safer Insecticides Natural and Unnatural Products with Quaternary Carbon Centers Natural and Unnatural Products with Quaternary Carbon Centers
California State University, Long Beach (Department of Chemistry and Biochemistry and the Department of Biological Sciences) Dr. Paul Buonora Dr. Mason and Dr. Archie The Howard Hughes Medical Institute