The Preparation Of β-thiocyanatopropenal And Their Applications In The Synthesis Of Thiophene Derivatives

The topic of this thesis mainly focused on the preparation of β-thiocyanatopropenaland their applications in the synthesis of thiophene derivatives. The thiocyanates areimportant intermediates in the organic synthesis, and usually employed as useful buildingblocks for constructing organic sulfides and sulfur heterocyclic compouds. Thiophenederivatives are found in many natural products and synthetic molecules, exhibitingfascinating pharmacological and biological activities and are widely used in medicine,pesticides, dyes, chemical reagent, polymer additives etc. The drugs containing thiophenederivatives have a great influence on antiphlogosis and analgesia, inhibition enzymeactivity and anti-viral, Especially in clinical research, more and more antibiotics ofthiophene derivatives have been used and played an important role in the development ofnew drugs. Further more, Clinical treatment has confirmed that the antibiotics withthiophene ring have better curative effect than the ones with phenyl homologues.Therefore, it is important to explore new methods for the synthesis of thiocyanates andthiophene derivatives.In this thesis, construction methods of the thiophene ring and the applications of thethiophene derivatives in the fields of medicine and materials in recent years werereviewed, as well as the utilization of thiocyanates in organic synthesis was introducedbriefly. The thesis emphasized on the efficient preparation of thiophene derivatives bythiocyanates under acidic condition. The Henry reaction between nitromethane andβ-thiocyanatopropenal which was a new type of sulfur reagent to access thiophenederivatives was also highlighted here. Compared with the previous work, this methodexerted several advantages: novelty, simple operation, mild reaction condition and easyseparation of the product. The major works were as following:(1) Synthesis of nine β-halo-α,β-unsaturated aldehydes as substrates from the simplyavailable materials by Vilsmeier reation. (2) Development of a new synthesis route for β-thiocyanatopropenal from β-halo enals inhigh yields. Using3-chloro-3-phenylacrylaldehyde as the mode substrate to optimizethe reaction parameters by change of reagent, solvent, reaction temperature (yield:up to92%).(3) One-Pot Procedure for thiophene derivatives from β-thiocyanatopropenal initiated byHenry reaction. Optimization the reaction conditions by change of solvent, base,reaction temperature. Then the scope of β-thiocyanatopropenal was explored. Theresults shown that Z configuration substrates were easier to cyclize than Econfiguration substrates, and the yield of cyclic substrates was up to71%.