RESUMO
Perfluororhodacyclopentane supported by PBP pincer ligand PBP-RhIII (CF2 )4 (2) was prepared from PBP-RhI -PPh3 (1) and tetrafluoroethylene (TFE). By scXRD analysis, it was revealed that the Rh-CF bond trans to the boryl ligand was largely elongated compared to the one in the apical position. Although M-CF bonds of perfluorometallacyclopentanes are known to be very stable, 2 shows high reactivity toward hydrogenolysis, iodinolysis and protonolysis, thanks to the strong trans-effect of the highly σ-donating boryl ligand. Analogous PCP pincer complex PCP-RhIII (CF2 )4 (4) showed slower reaction rate both in oxidative cyclization with TFE and hydrogenolysis of Rh-CF bond. Catalytic production of 1,1,2,2,3,3,4,4-octafluorobutane from two TFE and hydrogen in one pot was achieved via repetitive oxidative cyclization of TFE and Rh followed by the hydrogenolysis of Rh-CF bonds. This report demonstrates the possible application of PBP-pincer skeleton to the preparation of fluorinated compounds from TFE.
RESUMO
A new transformation pattern for enantioselective intramolecular hydroacylation has been developed involving an alkene isomerization strategy. Proceeding through a five-membered rhodacycle intermediate, 3-enals were converted to C3 - or C3 ,C5 -chirogenic cyclopentanones with satisfactory yields, diastereoselectivities, and enantioselectivities. A catalytic cycle has been theoretically calculated and the origin of the stereoselection is rationally explained.