Stereocontrolled Generation of the (2<i>R</i>) Chroman Core of Vitamin E: Total Synthesis of (2<i>R</i>,4′<i>RS</i>,8′<i>RS</i>)-α-Tocopherol

(2R,4′RS,8′RS)-α-Tocopherol (1) was prepared using, as the two key steps, a novel diastereoselective TiCl4-promoted (S)-sulfoxide-directed allylation of ketal 2 with allyl trimethyl silane 3 to efficiently generate the challenging (2R) stereocenter of the chroman moiety and a cross-metathesis reaction with olefin 4 to efficiently join the lipophilic alkyl chain present in the final target.