Double [3+2] Cycloaddition Of Pyridinium Ylide And The Preparation Of Novel Twisted Amide

There are two sections in this thesis:I) pyridinium ylide-involved double [3+2] cycloaddition and the study of its mechanism; II) the preparation of novel twisted amide.I). Pyridinium ylide-involved double [3+2] cycloaddition and the study of its mechanismAs a series of cycl[3,2,2]azines, pyrrolo[2,1,5-cd]indolizine and its derivatives, due to their high biological activities and novel structural characteristics, are attracting a lot of attentions of chemical practitioners. As a precursor of pyridinium ylide, pyridinium bromide is generally prepared from pyridine-containing compounds and N-alkylating agents. Pyridinium bromide is deprotonated under basic conditions to generate pyridinium ylide. Pyridinium ylide reacts with one molecule of dipolar partner to afford mono[3+2]cycloadduct, and it further reacts with another molecular of dipolar partner to afford double[3+2]cycloadduct. Pyrrolo[2,1,5-cd]indolizine and its derivatives, due to their high stereoselectivities and high biological activities, are attracting a lot of attentions of chemical practitioners.Based on that, this thesis is focused on the pyridinium ylide-involved double [3+2] cycloaddition and the study of its mechanism.1.4-Methoxy-substituted pyridinium bromide reacted with two molecules of maleimide using DBU as a base,to get the double[3+2]cycloadduct, and 16 decahydropyrrolo-[2,1,5-cd]indolizine compounds were prepared. All compounds were identified by IR, HRMS and NMR, and 4 of them were confirmed by X-ray diffraction method.2. N-methyl maleimide was choose as dienophile, and p-methoxypyridinium unsubstituted phenacyl bromide was used as the standard condition, the relative reaction rate of five p-methoxypyridinium substituted phenacyl bromides was determined by 1H NMR. Based on the analysis of Hammett plot, a reasonable reaction mechanism was proposed, and The initial Hammett analysis suggested that the most stable resonance form of pyridinium ylide is the one, the negative charge of which is widely dispersed in the pyridine ring.3. Pyridinium ylide-involved other double [3+2] cycloaddition was attempted to explore, including the expansion of substrate, and exploration of new reaction type. Differently substituted pyridines and halides was tried to form different pyridinium salts, and they are used to react with other dienophiles to get new products.II). The preparation of novel twisted amideTwisted amide is one type of amide, the amide bond of which is twisted. Based on that, the lone pair of nitrogen atom is not or only partially conjugated with pi-electrons of carbonyl group. It entitles the twisted amide new physical and chemical properties. The nitrogen of twisted amide has some propertied of amines, and the carbonyl group of which has some of ketones. From that, we are engaged to synthesize one new twisted amide.We used 4-bromoanisole and t-butylcyclohexanone as the starting materials, and one new twisted amide was prepared after many steps. The key step was optimized by trying different Lewis acids. New physical and chemical propertied of this twisted amide will be studied soon.