Enantiopure acyclic (E)‐ and (Z)‐configured allylic sulfoximines have been synthesized from N,S‐dimethyl‐S‐phenylsulfoximine and aldehydes by the addition− elimination−isomerization route through the intermediate generation of the corresponding (E)‐configured vinylic sulfoximines. Isomerization of the vinylic sulfoximines with DBU preferentially afforded the corresponding (Z)‐configured allylic sulfoximines, which were subsequently isomerized by DBU to preferentially yield the (E)‐isomers. Titanation of lithiated (E)‐configured allylic sulfoximines with ClTi(OiPr)3 furnished the corresponding bis(2‐alkenyl)diisopropyloxytitanium(IV) complexes, which reacted with aldehydes in the presence of ClTi(OiPr)3 with high regio‐ and diastereoselectivities at the γ‐position to give the corresponding (Z)‐anti‐configured δ‐N‐methylsulfonimidoyl‐substituted homoallylic alcohols in good yields. In the absence of ClTi(OiPr)3 at low temperatures, only one allylic moiety of the bis(alkenyl)diisopropyloxytitanium complex is transferred to the aldehyde. In this way, a cyclic lithiated allylic sulfoximine has been converted with high regio‐ and diastereoselectivity to the corresponding homoallylic alcohols bearing a vinylic sulfonimidoyl group. Titanation of lithiated (E)‐ and (Z)‐configured allylic sulfoximines with ClTi(NEt2)3 afforded the corresponding mono(2‐alkenyl)tris(diethylamino)titanium(IV) complexes, which reacted with aldehydes with moderate to high regioselectivities and high diastereoselectivities preferentially at the α‐position to give the corresponding syn‐configured β‐N‐methylsulfonimidoyl‐substituted homoallylic alcohols along with the (Z)‐anti‐configured δ‐N‐methylsulfonimidoyl‐substituted homoallylic alcohols in good yields. In this way, the cyclic lithiated allylic sulfoximine was converted with high regio‐ and diastereoselectivity to the corresponding isomeric homoallylic alcohols bearing an allylic sulfonimidoyl group. In the case of mono(alkenyl)tris(diethylamino)titanium(IV) complexes, the regioselectivity of their reactions with aldehydes has been found to depend on the size of the substituent at the CC double bond and the aldehyde, as well as on the configuration of the double bond. Reaction of racemic lithiated N‐methyl‐S‐(3,3‐diphenyl‐2‐propenyl)‐S‐phenylsulfoximine with ClTi(OiPr)3 afforded the corresponding bis(alkenyl)diisopropyloxytitanium(IV) complex. X‐ray structure analysis revealed a distorted octahedral cis,cis,cis‐configured bis(2‐alkenyl)diisopropyloxytitanium(IV) complex, in which the allylic moieties are coordinated in a bidentate fashion through C‐α and the N atom to the Ti atom, both having the relative configuration RSSC. In solution, the titanium complex shows fluxional behavior, which is characterized by topomerization of the isopropyloxy groups and allylic moieties. The exchange of the latter occurs with retention of the configuration at C‐α.

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Variable-temperature (1)H and (13)C NMR spectroscopy of the sulfonimidoyl-substituted allyltitanium(IV) complexes E-1a-c and Z-1a-c, which carry diethylamino groups at the Ti atom, revealed a fast 1,3-C,N-shift of the Ti atom, leading to an equilibrium between the epimeric Calpha-titanium allyl complexes A and C and the N-titanium allyl aminosulfoxonium ylide B. Based on these findings a model for the reactions of E-1a-c and Z-1a-c with aldehydes is proposed, which features regio- and diastereoselective reactions of the N-titanium ylide B at the alpha-position and the Calpha-titanium complex A at the gamma-position. Model ab initio calculations of the methylene and allyl (dimethylamino)sulfoxonium ylides 10 and 14, respectively, revealed short Calpha-S bonds, a stabilization by both electrostatic interaction and negative hyperconjugation, and a low Calpha-S rotational barrier. The ylides preferentially adopt Calpha-S and Calpha-N conformations in which the lone pair orbital at the Calpha atom is periplanar to the S=O bond and that at the N atom periplanar to the Calpha-Ph bond. Variable-temperature NMR spectroscopy of the sulfonimidoyl-substituted alkyltitanium(IV) complex 16, which carries diethylamino groups at the Ti atom, revealed a dynamic behavior leading to a complete topomerization of all four methylene hydrogens of the Calpha-ethyl groups. Two fast processes are held responsible for the topomerization of the hydrogens of 16. The first one is a reversible intramolecular beta-hydride elimination/alkene-Ti-H insertion with the intermediate formation of a complex between (Et(2)N)TiH and a 1-alkenyl sulfoximine, and the second one consists of a reversible 1,3-C,N-shift of the Ti atom in combination with a Calpha-S bond rotation. Interestingly, the room-temperature NMR spectra of the corresponding sulfonimidoyl-substituted alkyltitanium(IV) complex 17, which carries isopropoxy groups at the Ti atom, give no indication of a similar dynamic behavior of this complex.