Thesis (doctoral)--Freie Universität Berlin, 1981.

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.

1,2-Diazetidine is a four-membered ring heterocyclic compound which has two adjacent nitrogen atoms. However, the syntheses of C-unsubstituted 1,2-diazetidines are rarely reported in the literature. C-unsubstituted 1,2-diazetidines were synthesized through an operationally simple intermolecular vicinal disubstitution reaction between 1,2-dibromoethane and hydrazine with N-arylsulfonyl as the protecting group. Several different types of C-unsubstituted 1,2-diazetidines derivatives were synthesized with either two of the same or two different N-arylsulfonyl groups. The electronic and steric properties were analyzed using Raman spectroscopy and computational calculations. Then, several synthetic applications were demonstrated with 1,2-ditosyl-1,2-diazetidine (DTD). As a synthetic application, a nucleophilic ring-opening reaction of the diazetidine was identified through various thiol selective cleavage of the N‒N bond, resulting in the stereoselective formation of a new class of N-sulfenylimine. Furthermore, DTD underwent FeBr2-catalyzed retro [2+2] ring-opening and sustained release of formaldimine (FI) in situ in a reaction medium which is the simplest imine used amidomethylative reagent. Therefore, the effective available concentration can be controlled at low levels in the reaction medium. Moreover, the sustained release of FI was able to interrupt the amidomethylative process with α- methylstyrene and FeBr2 as the catalyst and resulted in 4-phenyl-1,2,3,6-tetrahydropyrimidine (PTPH) as a product. The PTPH is a neurotoxic compound used to induce Parkinson’s disease in animal models. In addition, sustained release of FI allowed to switch the selectivity from alkene, imine, and imine arrangement into alkene, imine, and alkene arrangement in [2+2+2] cycloaddition reaction and led to form piperidines as a product which is the most observed heterocycle in marketed drug molecules. Chromane derivatives are observed in pharmaceuticals and natural products. Chirally pure chromane derivatives were synthesized through ruthenium-catalyzed chiral transient directing-mediated enantioselective C–H activation. Interestingly, a phosphate was involved in the deprotonation step, the rate-determining step with a 5.3 KIE value.