Studies In Palladium Catalyzed Carbohalogenation Chemistry And Annulation Reaction

The development of general and efficient methodologies for the synthesis of complexmolecular skeletons is the central focus of mordern organic chemistry. Haloalkynes areattractive starting materials in palladium-catalzyed transformations because they are highlyreactive and readily available from the inexpensive acetylides. Plus, they can tolerate variousreaction conditions and generally do not require additional oxidant or base. Halogen atomcould activate the triple bond and as the leaving group, the triple bond occurs thecross-coupling reaction with alkynes, akenes and amines etc; The halogen atom as thedirecting group which proceeds the nucleophilic addition reaction. The halogen atom as theactivating group which proceeds the annulation addition.In this context, we describe herein our recent explorations in the field of haloalkynechemistry. An array of broadly useful coupling methodologies has been developed for theformation of C(sp)-C(sp~2)、C-N and C-Br bonds etc. We further describe the application ofthese methods to the syntheses of complex systems, including the haloalkenyne, cyclobutylbromide, Bromofluoroalkenes, and heterocycles. Our research on activation andfunctionalization of alkynes has led to a series of new results which will be presented in thefollowing five chapters.In chapter1, we have introduced the reaction features of haloalkynes, the effectivesynthesis methods and the progress on selective C-C, C-N and C-X (X=I, Br, Cl) bondformation from haloalkynes and functionalization of haloalkynes has led to a series of alkynes,alkenes, Ynamides and cycloaddition products etc. Finally, introduces the significane of thisresearch subject.In chapter2, we have discovered a novel type of palladium-catalyzed cross-couplingreaction between bromoalkynes and internal alkynes. Direct cis-addition of bromoalkynes tovarious alkynes were found to take place to give difunctionalized enynes as products withPd(II) as a catalyst. The reaction condition was extremely easy, providing a facile method forthe synthesis of bromo alkenynes. Furthermore, an unusual mechanism was proposed torationalize the observations.In chapter3, The palladium-catalyzed intermolecular reaction of haloalkynes withnorbornene derivatives leads to7-alkynyl norbornane products. Forming a non-classical“norbornonium” cation or bridging palladium, which can rearrange the substituent at2-C to7-C, and then furnishing a7-C functionalization is key for the success of this reaction. In thesimilar condition, the [2+2] cycloaddition of haloalkynes with cyclooctene has been achieved in moderate to good yields.In chapter4, Difunctionalization of terminal alkynes was achieved with AgF and NBS ashalogen sources. The presence of the halide moiety greatly enhances the reactivity of the vinylfluoride compounds and probably can be transformed into various products that are difficulteven impossible to obtain via direct fluorination. Meanwhile, the monofluoroalkenes werefacilely synthesized via a highly chemo-and regioselective fluorination of electron-deficientC-C triple bonds using AgF as fluorinating reagent in good yields.In chapter5, we have developed a new strategy for the synthesis of bromoacrylamidesand polysubstituted iminopyrrolinones in good to excellent yields from readily availablestarting materials. This chemistry proceeds smoothly under the optimal reaction conditionsand various functional groups can be tolerated with exceptional selectivity. The methodologyis highly practical and it provides a straightforward approach to a series of5-iminopyrroloneand haloacrylamides in regioselective manner.In addition, a new general carbohalogenation procedure to couple haloalkynes underpalladium catalysis is described. The bromoalkynylation reaction is chemoselective andallows preparation of a vast array of simple and high functionalized internal alkynes in highyields. The palladium-catalyzed haoloalkynes, cycloalkenes, carbon monoxide and methanolprovides an efficicent approach to interesting f δ-alkynyl-γ-ester compounds in good yields.The part of the work is coming soon.Finally the research summary, research achievements, and acknowledgement areintroducted successively.