Metallated 2‐Alkenyl Sulfoximines in Asymmetric Synthesis: Regio‐ and Stereoselective Synthesis of Highly Substituted Tetrahydrofurans

Abstract

AbstractStarting from the enantiopure 2‐alkenyl sulfoximines 4/5 and epi‐4/5, a one‐pot procedure has been developed for the synthesis of tri‐ and tetrasubstituted tetrahydrofuran derivatives with excellent control of all relevant aspects of their structural description. The cyclization of the intermediate γ‐hydroxyvinyl sulfoximines is strictly regioselective due to the electronic properties of the double bond involved. The absolute configuration at C‐2 can be selected at will by a proper choice of the corresponding lactaldehydes 14 or ent‐14 respectively. The absolute configuration at the 3‐ and 4‐positions of the THF derivatives is under control of the sulfoximine moiety during aldehyde uptake, whereas their relative configuration is fixed due to the 1k relative topicity of attack of the reactands involved in their generation. The configuration at position 5 is determined mainly by the release of 1,3‐allylic strain and is therefore the only stereogenic centre under substrate control. This becomes obvious in two cases (17a and 18a) where stereocontrol at this position is diminished. Here, the absence of a 3‐methyl group as a control element reduces the energetic difference between the Re‐ and the Si‐side attack.