1,3-HYDRON TRANSFER IN SOME 5-SUBSTITUTED OR 7-SUBSTITUTED 1-METHYLINDENES - REACTION-RATES AND KINETIC ISOTOPE EFFECTS

Rate constants and primary deuterium kinetic isotope effects (KIEs) ha ve been determined for the base-catalysed 1,3-hydrotropic rearrangemen ts of 1-methyl-5-nitroindene (12), 1-methyl-7-nitroindene (13), 5-meth oxy-1-methylindene (14) and 5-fluoro-1-methylindene (15) in o-dichloro benzene at 20 degrees C. The tertiary amine 1,4-diazabicyclo [2.2.2]oc tane( DABCO) was used as catalyst. The kinetics were followed by polar imetry using the isotopic quasi-racemate method. The rearrangement of 13 was also investigated by H-1 NMR kinetic experiments. The reaction rate correlates, as expected, with the electronic effect of the substi tuent ranging from a large increase for the 5-nitro substrate to a sma ll decrease for the methoxy compound as compared with the unsubstitute d 1-methylindene. The KIEs vary as predicted from the Melander-Westhei mer postulate showing an increase with reaction rate from 5.57 to 8.56 . The syntheses of the (+)-(S)-form of the 5- or 7-substituted indenes and the (-)-(R)-form of the deuteriated analogues are also reported.