Sulfur-Participated Cyclization Reaction

The nucleophilicity of sulfur anion is stronger than oxygen anion due to its atomic radius and sulfur is also inclined to form sulfonium ion intermediate in organic synthesis. Sulfur participation is significant in organic synthesis to construct the heterocyclic compounds. Thio-Claisen rearrangement (TCR), classically a [3, 3] sigmatropic rearrangement in the allyl vinyl sulfides leading to a homoallyl thiocarbonyl unit, has received considerable attention in the past decades. In this dissertation, a series of indene derivatives and thiophene derivatives were synthesized via the sulfur participation strategy.The indenes moiety is present in a class of drug candidates possessing interesting biological activities, and also could be principal precursors in organic synthesis. In the second section of this dissertation, an intramoluclar addition of sulfur-participated Nazarov-type cyclization affording 3-thio-1H-indenes was reported. As a result of the ready availability of starting materials and the simple and convenient operation, this type of reaction presented here has potential utility in organic synthesis.In the third section of this dissertation, A sulfur-assisted five-cascade sequential reaction, wherein the in situ-generated allenyl allyl sulfides undergo thio-Claisen rearrangement, intramolecular Michael addition, and 1, 5-proton migration aromatization to obtain allyl thiophen-2-yl acetates, propionates, and ketones as thefinal products, was reported. Application of this efficient method for the synthesis of potentially pharmaceutical compounds also might be useful for the pharmacists.