MULTIDIMENSIONAL NMR-STUDY OF TRIS(INDENYL)METHYLSILANE - MOLECULAR-DYNAMICS MAPPED ONTO A HYPERCUBE

(Trimethylsilyl)indene exists as a pair of enantiomers which interconv ert by means of Me(3)Si migrations. The mechanism involves successive [1,5]-suprafacial sigmatropic shifts via the corresponding isoindene, which can be trapped with tetracyanoethylene as the Diels-Alder adduct , 7. The X-ray crystal structure of 7 reveals that the TCNE approaches from the opposite face to the Me(3)Si substituent. Tris(indenyl)methy lsilane, 5, also undergoes a series of [1,5]-silatropic shifts which i nterconvert the RRR, RRS, RSS, and SSS isomers, where the R and S labe ls refer to the absolute configuration of C(1) in each indenyl ring. B y use of H-1-H-1 COSY, H-1-C-13 and H-1-Si-29 shift-correlated NMR spe ctra, the proton and carbon-13 nuclei in all four different indenyl ri ng environments can be unequivocally assigned. The molecular dynamics of 5 have been elucidated by means of 1D-selective inversion experimen ts together with 2D-EXSY data, and the exchange pathways between inden yl sites can be conveniently mapped onto a hypercube. Moreover, 5 yiel ds a triple Diels-Alder adduct, 12, with TCNE; the Si-CH3 H-1 NMR reso nance in 12 is found at -1.8 ppm suggesting that this methyl lies insi de a cavity formed by the three phenyls.