, 27 (s, 5H, Cp*), 4.25 (s, 5H, Cp), 2.23 (s, 3H, CH3CO), 2.11 (s, 3H, CH3CO*), 1.78 (d, J = 6.7 Hz, 3H, CH3*), 1.49 (d, J = 6.7 Hz, 3H, CH3), 0.44 (s, 9H, Si(CH3)3*), 0.43 (s, 9H, Si(CH3)3). 13 C NMR (75.4 MHz, CDCl3): ? (ppm) 170.0 (s, C=O*), 169.9 (s, C=O), 135.4 (d, J = 278.2 Hz, C3), 135.1 (d, J = 278.2 Hz, C3*), vol.4, 1039.

, mg, 0.15 mmol, 1.00 equiv), the title product was obtained as an orange oil (64.0 mg, 81%). A mixture of diastereoisomers in a 1:4.5 ratio was identified by NMR, otherwise analytical data analogous to racemic compound, in CHCl3). ee = 99.5%, de = 63%. The enantiomeric and diastereoisomeric ratios were determined on

, hexane/iPrOH: 99.5:0.5, 0.25 mL/min, 5 °C, ? = 254 nm, t (S, Rp) = 35.71 min, t (R, Sp) = 37.91 min, t (S, Sp) = 40.72 min

, mL) at rt. After 1 h, volatiles were removed under vacuum using a rotary evaporator to give the crude product. This was triturated with Et2O (2 mL) and filtrated. The resulting solids were washed with Et2O (2 x 2 mL) and dried under high vacuum to give the title product as an orange solid

. Rf, with 10 drops of NEt3 for 10 mL of eluent, TLC plate first dipped into EtOAc-NEt3 (50:50) and dried) = 0.00. Mp 149-153 °C (decomp.). ?max (film)/cm ?1 3445 (br), vol.724, pp.701-702, 1045.

. Mhz, , p.125

. Mhz, 1 (s, Cp), 76.0 (s, C5), 68.9 (s, CH), 64.5 (d, J = 14.9 Hz, C3), 51.8 (s, NMe3), CDCl3): ? (ppm) 134.9 (d, J = 276.5 Hz, C2), 83.3 (d, J = 17.7 Hz, C1), vol.76

, By following a similar protocol, starting from (R,Sp)-14 (35.5 mg, 0.07 mmol, 1.00 equiv), the title product was obtained as an orange solid (45.3 mg, quant.). Analytical data analogous to racemic compound

, HPLC Chromatograms of compounds, p.16

, hexane/iPrOH: 99.5:0.5, 0.25 mL/min, 5 °C, ? = 254 nm, t (S,Rp) = 35.71 min, t (R,Sp) = 37.91 min, t (S,Sp) = 40.72 min

, 25 mL/min, 5 °C, ? = 254 nm, t (S,Rp) = 35.71 min, t (R,Sp) = 37.91 min, t (S,Sp) = 40.72 min, (R,Rp) too low to be identified. ee = 99.5%, de = 63%, N. J. Nielsen J. Organomet. Chem, vol.542, pp.281-283, 1997.

K. Plevová, B. Mudráková, and R. ?ebesta, , vol.50, pp.760-763, 2018.

M. Tazi, M. Hedidi, W. Erb, Y. S. Halauko, O. A. Ivashkevich et al., Organometallics, vol.37, pp.2207-2211, 2018.

G. Sheldrick, Acta Crystallogr. Sect. A, vol.71, pp.3-8, 2015.

G. Sheldrick, Acta Crystallogr. C, vol.71, pp.3-8, 2015.