Sulphinyl group

Generation of anions a to the sulphinyl group takes place also in 1 -alkenyl sulphoxides and can easily be achieved by using such bases as LDA383-385, t-BuLi386 and n-BuLi (for allenyl sulphoxides)387. 

Posner and coworkers have published a series of papers in which they described a successful application of the Michael reaction between a variety of carbanionic reagents and chiral cycloalkenone sulphoxides 557 to the synthesis of chiral organic compounds (for reviews see References 257, 649, 650). In several cases products of very high optical purity can be obtained. Subsequent removal of the sulphinyl group, serving as a chiral adjuvant, leads to optically active 3-substituted cycloalkenones 558 (equation 356 Table 27). 

In the equilibrium mixtures of thiane oxide (2) and 1,3-, 1,4-dithiane dioxides (3) and (4), the axial conformers are present predominantly over the equatorial conformers at low temperatures (— 90 °C). For instance in the monoxide (2) a ratio of 62% axial and 48% equatorial conformers has been observed. The prevalence of the axial conformers in the sulphoxides (2) and (4) has been explained to be due to hydrogen bonds between the oxygen in the axial sulphinyl group and the hydrogen atom at the 3-position as shown in Scheme 7121 127. 

Diverse series of diphenyl sulphoxide (DPSO) complexes of Mn(II), Fe(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Ca(II), Al(II) and Mg(II) with various large anions have been reported187-191. The complexes have the general formula M(DPSO)6(Anion) where M is the metal cation. The reflection spectra in the visible and near-IR region indicate an octahedral configuration around the metal ion surrounded by the DPSO molecules. Comparison with the spectra of DMSO complexes shows that they have almost identical structures. IR spectra indicate that the oxygen atom in the sulphinyl group is the donor atom in all these complexes. 

The behaviour of polydentate ligands containing sulphinyl groups has received much less attention. Giesbrecht and Osorio203 have reported the coordination compounds of bivalent transition metal (Mn2+, Co2+, Ni2+, Cu2 +, Cu2+, Zn2+) perchlorates with 2,2 -sulphinyldiethanol (SDE). 

The dianion of 2-carboxyethyl phenyl sulphoxide 362 undergoes alkylation at the a-position to the sulphinyl group (equation 205). 

Thus, the enantiomeric contents in a pair of sulphoxides can be determined by the H NMR chemical shifts in the methine or methylene protons in the two diastereomeric complexes which are stabilized by the hydrogen bond between the hydroxyl and the sulphinyl groups (Scheme 13). Similarly, the enantiomeric purity and absolute configurations of chiral sulphinate ester can be determined by measuring the NMR shifts in the presence of the optically active alcohols. ... 

Ferrocene is best deprotonated by f-BuLi/f-BuOK in THF at 0 since BuLi alone will not lithiate ferrocene in the absence of TMEDA and leads to multiple lithiation in the presence of TMEDA. In the example in Scheme 134, a sulphur electrophile and a Kagan-Sharpless epoxidation lead to the enantiomerically pure sulphinyl ferrocene 278. The sulphinyl group directs stereoselective ortholithiation (see Section I.B.2), allowing the formation of products such as 279. Nucleophilic attack at sulphur is avoided by using triisopropylphenyllithium for this lithiation. 

The IV-sulphinyl group in Davis sulphinimines 58a and 58b117, in analogy to the alkoxycarbonyl group in 56, hampers ring closure to /3-lactam, as independently reported by Staas and coworkers118 (equation 36) and Soloshonok and coworkers119 (equation 37). 

In contrast, reduction of the corresponding enamide with Na(CN)BH3 was much more selective giving a single enantiomer, derived by attack of the hydride from the opposite side of the bulky sulphinyl group (Scheme 91). 

A somewhat different type of approach to chiral aldol products uses a sulphinyl group as a removable chiral auxiliary. Although the chemical yields were modest, the optical purities of the products (54 - 78%) must be regarded as impressive for the difficult case of chiral 8-hydroxy ketones with no a-alkyl substituent (Scheme 35).17 ... 

There are two new examples of the use of chiral sulphinyl groups for induction of optical activity, in one case during the reduction of an imine to an amine with UAIH4 and in the other case during the alkylation of an aldehyde before cycliza-tion to an epoxide.In the latter case the reaction has been used as part of a sequence leading to the insect pheromone disparlure. N-Tosylsulphilimines (76) are converted in good yield and with high stereoselectivity into rrans-disubstituted oxirans (77) on reaction with NaH and an aromatic aldehyde. 

The substituted sulphoxide (74) could be converted into the carbanion, which then underwent alkylation. Under acidic conditions the sulphinyl group and the methylthio-group could be removed, affording aldehydes in good yield. This reaction serves as a homologation reaction. Sulphinyl ylides also undergo acylation, as illustrated by the reaction of dimsylsodium... 

Sulphinyl ylides react with carbonyl compounds, usually resulting in overall addition to the carbonyl group and formation of hydroxy-sulphoxides. Additional examples have been reported in the past two years. Vig et al. have reported numerous examples of conjugate addition of a sulphinyl ylide (75) to methyl vinyl ketone and other conjugated olefins. These workers were able to remove the sulphinyl group... 

Thionylaniline reacted with diphenyldiazomethane under photochemical conditions to afford triphenylketimine via, it was proposed, addition of diphenylcarbene to the sulphinyl group and then extrusion of SO (Scheme 4). The presence of tetraphenylethylene and other fragments... 

Stereochemical studies concerning oc-sulphinyl carbanions have clarified the conflict of interpretation of recent years of kinetic preference in exchange of diastereotopic protons a to the sulphinyl group. Studies of cyclic sulphoxides have shown that small changes in dihedral angle... 

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