Studies On The Tandem [4+2] Cyclization Reactions Of Ketene Dithioacetals With Acyl Chlorides

y-Pyrones?4H-pyran-4-ones?are an important class of heterocyclic compounds which are widely found in natural products and bioactive compounds.y-Pyrones are also useful synthetic intermediates and widely used in organic synthesis.y-Pyrones could be synthesized from,for example:?1?cyclization of 1,3,5-tricarbonyl compounds;?2?cyclization of diacetylene ketones compounds;?3?DMAP?4-?dimethylamino?pyridine?/Lewis acid cooperatively mediated formal[3+3]annulation of ?,?-unsaturated alkynyl carboxylic acids with 1,3-dicarbonyl compounds;?4?the reaction of acetylketenes with vinyl ethers via[4+2]cyclization;?5?multicomponent tandem reactions of aryl aldehydes,malononitrile and active methylene compounds etc.However,most of these reactions often encountered the limitations such as the use of transition-metal catalysts,special substrates and required several steps with relatively lower yields.More efficient and practical method for the synthesis of y-pyrones is still highly desirable.In recent years,our group has been devoted to the study on ketene dithioacetal chemistry,and has achieved relevant results in ?-functionalization reactions,Vilsmeier reactions,C-S bond breaking,cyclization reactions,multicomponent domino reactions and so on.In view of the convenient utilizations of widely available acyl chlorides,this thesis provides a novel formally tandem[4+2]heterocyclization of ketene dithioacetals via the ?-diketone intermediate.Furthermore,the 2-arylation and amylation y-pyranone were completed using the synthesized y-pyrones as the raw material.The simple synthesis of various y-pyrones and their derivatives are realized,which provides an important library of y-pyrones compounds for natural product chemistry and pharmaceutical chemistry.Thus,it provide an efficient and useful method for the construction of poly-substituted y-pyrones and their synthetic applications in the synthesis of versatile heterocycles.The structures of the synthesized y-pyrones in this thesis were confirmed by ¹H-NMR,¹³C-NMR,high resolution mass spectrometries and single crystal ray diffraction experiments.