Ac onceptionally new strategy for the asymmetric (2R-selective) synthesis of a-tocopherol (vitamin E) was developed. In the stereocontrolled key step, ap rochiral spiro[chromane-2,3'-cyclobutanol] unit is effectively desymmetrized under CÀCb ond activation in an unprecedented iridium-catalyzed transformation using (S)-DTBM-SegPhos as ac hiral ligand (e.r.9 7:3). To complete the synthesis, the side chain was attached through Ru-catalyzed cross-metathesis employing an alkene derivedfrom (R,R)hexahydrofarnesol. To suppress epimerization during the final hydrogenation, PtO 2 had to be used as ac atalyst instead of Pd/C.I na na lternative approach( employing a propargyl-substituted spiro-cyclobutanol), the side chain was constructed prior to the Ir-catalyzed ring fragmentation (> 99:1 d.r.) through enynec ross-metathesis (usinga n alkene derived from (R)-dihydrocitronellal) followed by Crcatalyzed 1,4-hydrogenation and (diastereoselective) Pfaltz hydrogenationo ft he resulting triple-substituted olefin. The work demonstrates the potentialo fi ridium catalysis for enantioselective CÀCbond activation.Scheme1.Retrosynthetic analysis of a-tocopherol (1)b ya symmetricfragmentation(C ÀCb ond activation) of aspirocyclobutanol of type 3.

We report the FeCl3-mediated direct addition of electron-rich arenes to the C2-position of electrophilic N-Ac indoles under mild conditions (room temperature, air). No functional group is required on the arene nucleophile: one of its C-H bonds is added to the C2[double bond, length as m-dash]C3 double bond of the indole nucleus in a Friedel-Crafts-type reaction. This dearomatisation process delivered a broad range of C2-arylated indolines.