FLUOROSELENENYLATION OF ACETYLENES WITH XENON DIFLUORIDE-DIORGANYL DISELENIDES - SYNTHESIS AND STRUCTURE ELUCIDATION OF FUNCTIONALIZED VICINAL (E)-FLUORO(ORGANYLSELENO)OLEFINS

We carried out the fluoroselenenylation of hex-3-yne with xenon difluo ride and functionalized diselenides (dimethyl acetal- and carboxylic a cid ester-substituted) to the corresponding substituted vicinal (E)-fl uoro(organylseleno)olefins. Consecutive reactions afforded crystalline 2,4-dinitrophenyl-hydrazone and carboxylic acid derivatives. Nonfunct ionalized vicinal (E)-fluoro(organylseleno)olefins were alkylated with trimethyloxonium tetrafluoroborate, triethyloxonium tetrafluoroborate , and methyl trifluoromethanesulfonate to the corresponding fluoroalke nyldiorganylselenonium salts which were characterized either as tetraf luoroborate or as tetraphenylborate salts. X-ray analysis of [(E)-4-fl uorooct-4-en-5-yl]dimethylselenonium picrate (11) proved unambiguously that the fluoroselenenylation of acetylenes with XeF2-R(2)Se(2) and X eF2-PhSeSiR(3) reagents proceeds via trans additions.