Dedicated to Professor Frantis ˇek Turec ˇek on the occasion of his 60th birthday
Lewis base catalysed enantioselective allylation of aldehydes 1 with allyltrichlorosilanes 2 (Scheme 1) has become an efficient tool for C À C bond formation, thereby providing a robust alternative to the use of allylboranes carrying stoichiometric amounts of chiral auxiliaries. [1] The resulting homoallylic alcohols 3 are popular building blocks in targetoriented synthesis. However, in contrast to the more widely known and better-developed boron analogues, the synthetic applications of allyltrichlorosilanes are currently limited to simple alkyl homologues (R 2 = alkyl). Recently, we have demonstrated that alcohols 3, resulting from the addition of g-substituted allylsilanes 2, can themselves serve as efficient allylating reagents for aldehydes 4, which has broadened the scope of the method considerably. [2] A further advancement can be achieved by attaching additional functionality to allylsilane 2, and thus to the resulting alcohol 3, that will enable further synthetic development. [3] Herein, we introduce the new bifunctional allyldisilane 6 and demonstrate its applicability in a highly stereoselective triple allylation of al-dehydes, resulting in a stereocontrolled construction of trisubstituted tetrahydrofurans 8 (Scheme 2).
[a] O.