Pakorn BovonsombatRungkarn RujiwarangkulThanathip BowornkiengkaiJuthamard LeykajarakulMahidol University. Internationa College. Science Division.2015-01-282018-10-262015-01-282018-10-262015-01-282007https://repository.li.mahidol.ac.th/handle/123456789/32894Thailand Research Expo 2007, September 7-11, 2007, Bangkok, ThailandA facile methodology for the formations of α -chloro, α -bromo and α -iodo cyclic enones and linear enals has been developed. In our method, a combination of pyridine or pyridine-Noxide, and various N-halosuccinimides are employed to convert enones or enals in various solvents at room temperature to α -haloenones or α -haloenals. Previously, α -iodination of enones, both cyclic and linear, could be affected by small amounts of pyridine and stoichiometric iodine.(1) α -Iodination of several cyclic and linear enones were also reported to be effective with combination of iodine and excess quantities of pyridine using carbon tetrachloride as co-solvent.(2)Other reagents for α -iodination of enones include morpholine,(3) and pyridinium dichromate (PDC) and iodine.(4) With linear enones, the combination of pyridine and I2 required refluxing acetonitrile to obtain a maximum 62% yield for (Z)-4-iodo-4-hexen-3-one.1 With PDC and iodine, (E)-4-hexen-3-one reacted to yield less than 5% conversion to its α -iodo analogue.4 Extending the reactions to linear enones and to α -bromination and α -chlorination are limited due to low yields and uses of toxic bromine and chlorine. Previous methods for α -chlorination include hydrochloric acid and m-chlorobenzoic acid.(5) Reagents for α -bromination are iodobenzene diacetate with tetrabutylammonium bromide,(6) and Rhodium (III) complex combined with acid halides or benzyl halides.(7) In our general methodology for α -halogenation of both cyclic enones and linear enals, α - halogenations proceeded facilely with good to excellent yields and with retention of geometry across the double bond for the linear enals and also with retention of the sensitive aldehyde group.engMahidol Universitya-HalogenationsenonesenalsN-halosuccinimidespyridinepyridine-N-oxideProceeding Book