The Applications Of Alkylthio Activated Conjugated Enynes Compounds In Organic Synthesis

Due to not only including the basic structures of olefins and alkynes but also possing unique conjugation property between carbon-carbon double bond and carbon-carbontriple bond, conjugated enynes are a kind of very important building blocks in organic synthesis, and have been applied in various fields. While conjugated enynes with electron-donating substitutes can have some special characters due to the effect of electron-donating groups, and are more important organic synthetic intermediate. In contrast to the extensive studies on the common conjugated enynes, the investigations on conjugated enynes with electron-donating substitutes remained poorly explored. So it is very necessary to study the characters and extend applications of this kind of conjugated enynes with electron-donating substitutes.In our recent research on the synthetic applications of a-acetyl ketene-S,S-acetals and their analogues, a series of conjugated enynes with electron-donating alkylthio groups were obtained in high yields. To get insight into the property and synthetic applications of this kind of alkylthio activated enynes, the addition reactions of alkylthio activated enynes with nucleophiles and electrophiles, the coupling reaction of alkylthio activated enynes with aryl aldehydes and the self-coupling reaction of alkylthio activated enynes were invesigated and the main results are listed as follows.The addition reactions of alkylthio activated conjugated enynes compounds with carboxylic acids, thiols and aromatic amines were carried out, respectively, and the corresponding enol esters, vinyl sulfides and benzo[b][l,4]diazepines were obtained in good yield. The above experimental results revealed that the addition reactions proceeded in a highly chemo- and regioselective manner, and afford the corresponding Markovnikov addition products.In the presence of TiCl4, the coupling reaction of alkylthio activated conjugated enynes with aryl aldehydes were performed and regioselectively generated the corresponding (E/Z)-l,5-dihalo-l,4-dienes compounds. These dihalodiene compounds can are potentially useful intermediates in organic synthesis due to the multifunctionality in the molecules.By the oxidative self-coupling reaction of alkylthio activated conjugated enynes, several series of π-conjugated nonaromatic all-carbon backbones organic moleculars with the electron-donating alkylthio substitutes on the conjugated chain were prepared, and especially synthesized the first heteroatom-substituted expanded radialene molecule with dithiolanylidene groups as strongly donor termini. More importantly, owing to the introduction of the strong electron-donating alkylthio groups, per(alkylthiolated) expandedradialene shows an extremely strong intramolecular push-pull interaction and enhanced macrocyclic cross-conjugation. These results indicated that the conjugated enynes with electron-donating alkylthio groups could be new kinds of important organic synthetic intermediates in materials chemistry.The a-functionalized ketenedithioacetals, α-Iodo/bromo/nitro ketenedithioacetals, were prepared in high yields under mild reaction conditions by the iododecarboxylation reaction of a-carboxylate ketenedithioacetals and the bromo/nitrodeacetylation reactions of a-oxo ketene dithioacetals. These results further confirmed the electrophilic nature of the a-carbon atom on a-oxo ketene dithioacetals. These a-functionalized ketenedithioacetals have the potential to be used as important new intermediates in organic synthesis.The intramolecular [2+2] photocyclizations of bis(alkenoyl)ketenedithioacetals were achieved by the irradiating with high-pressure mercury lamp, and obtained three isomeric compounds of substituted bicyclo[3.2.0]heptane-2,4-diones. The experimental results provided a sufficient proof that the above intramolecular [2+2] photocyclizations reaction may be mainly completed via a radical reaction process.