Fused-Ring Heterocycle Syntheses from Thiazole, Oxazole, Benzoxazole, and Benzothiazole Derivatives and Trifluoroacetylations of N-Methyl Cyclic Ketene-N,O/S-Acetals: Attempted Syntheses of Functionalized Polymers from Plant-Derived 5-(Hydroxymethyl)Furfural
Mississippi State University
Pittman Jr., Charles U.
Mead, Keith T.
Henry, William P.
Date of Degree
Dissertation - Open Access
There are two sections to this research dissertation. Part one includes syntheses of fused-ring heterocycles derived from thiazole, oxazole, benzoxazole and benzothiazole derivatives and trifluoroacetylations of in situ generated N-methyl cyclic ketene-N,O/Sacetals. Attempted functionalized polymer syntheses from plant-derived 5-(hydroxymethyl) furfural are discussed in part two. Three 2-methylthiazoles, 2,4,5-trimethyloxazole, 2-methylbenzoxazole and 2- methyl-benzothiazole were each reacted with benzoyl chloride in acetonitrile/triethylamine to generate benzyl-vinyl esters. Base hydrolysis of these benzyl-vinyl esters formed 2-(heterocyclic)-1-phenylethenols which exist in both ketoenol tautomeric forms. These tautomers were used as starting materials for fused-ring heterocycle syntheses. Each tautomeric pair react with dimethyl acetylenedicarboxylate in methanol giving the 5,6-ringused 8-benzoyl-5-oxo-5H-thiazolo-, 8-benzoyl-5-oxo-5H-oxazolo-, 4-benzoyl-1-oxo-1H-benzo[4,5]oxazolo- and 4-benzoyl-1-oxo-1H-benzo[4,5]thiazolo [3,2-a]pyridinecarboxylate derivatives. Two novel 5,7-ringused 9-benzoyl-2,3- dimethyl-5,6-dihydrothiazolo- and 9-benzoyl-2,3-dimethyl-5,6-dihydrooxazolo[3,2-a] azepine-5,6,7,8-tetracarboxylates formed when the tautomers formed from 2,4,5- trimethyl thiazole and 2,4,5-trimethyl oxazole were reacted with DMADC. These tautomers react with 1,3-diacid chlorides in acetonitrile/triethylamine affording the 5,6-ringused 8-benzoyl-6,6-dialkyl-6H-thiazolo- and 8-benzoyl-6,6- dimethy-6H-oxazolo-, 4-benzoyl-2,2-dimethyl-1H-benzo[4,5]thiazolo- and 4-benzoyl- 2,2-dimethyl-1H-benzo[4,5]oxazolo[3,2,-a]pyridinedione derivatives. Functionalized 5,6- ringused 8-benzoyl-6H-thiazolo- and 8-benzoyl-6H-oxazolo[3,2]pyrimidine-5,7- diones, and 4-benzoyl-1H-benzo[4,5]thiazolo- and 4-benzoyl-1H-benzo[4,5]oxazolo[3,2- c]pyrimidine-1,3(2H)-diones formed reacting the tautomers with N-chlorocarbonyl isocyanate in THF/triethylamine. Significant ring size and substituent effects were observed in trifluoroacetylations of in situ-generated cyclic ketene-N,O/S acetals. In situ-generated 3,4,4-trimethyl-2- methylene-oxazolidine, 3-methyl-2-methylene-oxazolidine and 3-methyl-2-methylene- 1,3-oxazinane each formed β,β-bistrifluoroacetylated products. However, 3-methyl-2- methylene-oxazolidine also afforded a γ-lactam by an iodide-catalyzed rearrangement of its β,β-bistrifluoroacetylated derivative. In situ-generated 3-methyl-2-methylenethiazolidine gave both β-mono- and β,β-bistrifluoroacetylation products. 5-(Hydroxymethyl)furfural synthesized from sucrose was converted to 2,5- bis(hydroxymethyl)furan (2,5-BHMF). 7-Oxanorbornene-type Diels-Alder adducts synthesized from 2,5-BHMF were used as monomers for both ring opening metathesis polymerizations (ROMPs) and polycondensations. ROMP, followed by polycondensation or vise versa were expected to give highly functionalized cross-linked polymers. ROMP of the monomers using three Grubbs’ 1st, 2nd and 3rd generation catalysts were unsuccessful due to the presence of hydroxymethyl groups at one or both bridgeheads that could coordinate Ruthenium. With one bridgehead methyl present ROMP proceeded. Low molecular weight polyesters were synthesized via polycondensation. One was crosslinked using ROMP, but not to its gel point.
De Silva, Hondamuni Ireshika Chathurani, "Fused-Ring Heterocycle Syntheses from Thiazole, Oxazole, Benzoxazole, and Benzothiazole Derivatives and Trifluoroacetylations of N-Methyl Cyclic Ketene-N,O/S-Acetals: Attempted Syntheses of Functionalized Polymers from Plant-Derived 5-(Hydroxymethyl)Furfural" (2012). Theses and Dissertations. 2361.