Cyclic ketene-N,N-acetal chemistry was explored. 2-Methylimidazoline and 2-methyl-1,4,5,6-tetrahydropyrimidine derivatives were prepared from the condensation reactions of diamines with nitriles under Lewis acid catalysis and used as the precursors of cyclic ketene-N,N-acetals including the N-methyl and N-acyl cyclic ketene-N,N-acetals. The reactions of 2-methylimidazoline with excess benzoyl chlorides in THF or MeCN in the presence of triethylamine generate N,N'-diacyl-beta-keto-cyclic ketene-N,N-acetals. The corresponding reactions of 1,2-dimethylimidazoline under the same conditions form the ring-opened (Z)-3-((2-benzamidoethyl)(methyl)amino)-3-oxo-1-phenylprop-1-enyl benzoates. The latter reactions feature the formation of carbon-carbon bonds, carbon-nitrogen bonds, and carbon-oxygen bonds in one operation. The reactions of 2-methyl-1,4,5,6-tetrahydropyrimidine with excess acid chlorides in Et3N/THF generate N,N-diacyl-cyclic ketene-N,N-acetals, with no further acylation on the exocyclic beta-carbons. In contrast, the reactions of 1,2-dimethyl-1,4,5,6-tetrahydropyrimidine under the same conditions form N-acyl-N'-methyl-beta,beta-diketo-cyclic ketene-N,N-acetals, with the dual acylations on the exocyclic beta-carbons. Significant double bond torsion and elongation were observed by the X-ray analysis of an example compound from the latter reactions. The reactions of 2-methylimidazoline and 2-methyl-1,4,5,6-tetrahydropyrimidine with 1,3-diacid chlorides, in the presence of Et3N in refluxing MeCN give highly functionalized potentially bioactive 1,8-naphthyridinetetraones. 2-Methylimidazoline and 2-methyl-1,4,5,6-tetra-hydropyrimidine can be viewed as tridentate nucleophiles which give four consecutive tandem nucleophilic attacks on electrophiles. The reactions of 1,2-dimethylimidazoline and 1,2-dimethyl-1,4,5,6-tetrahydropyrimidine with isocyanates in refluxing MeCN gave bicyclic pyrimidinediones. The reactions of N,N'-dimethyl cyclic ketene-N,N-acetals with various isocyanates generated push-pull alkenes which have never been reported. Significant elongations and torsions of the polarized carbon-carbon double bonds in the novel push-pull alkenes were observed using the X-ray crystallography. The stronger pushing effect of the six-membered cyclic ketene acetal portion in a push-pull alkene, versus the five-membered analog, was detected by reactivity differences for the first time.
| Identifer | oai:union.ndltd.org:MSSTATE/oai:scholarsjunction.msstate.edu:td-5185 |
| Date | 13 December 2008 |
| Creators | Ye, Guozhong |
| Publisher | Scholars Junction |
| Source Sets | Mississippi State University |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | Theses and Dissertations |
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