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The reactions of thioferrocenoylsilanes with organolithium reagents, dienes and reducing agents which afford α-silyl sulphides, dihydrothiopyranes and α-silyl ferrocenyl thiols, respectively, have been investigated. α-Silyl sulphides were further functionalised through carbodesilylation with aldehydes. We also report the synthesis of a new planar chiral thioferrocenoylsilane that gave good diastereomeric excess in the reaction with t-butyllithium, lithium lutidine and 2,3-dimethylbuta-1,3-diene. The 1,1′-bis-thioferrocenoylsilane, too unstable to be isolated, was trapped in situ with dienes.

By means of low-temperature NMR spectra, it is demonstrated that dimesityl sulfine (Mes2CSO) adopts in solution the same chiral propeller conformation (C1 symmetry) determined by X-ray diffraction in the crystalline state. With the help of MM calculations, it has been also shown that a correlated rotation (cog wheel effect) of the two mesityl rings reverses the molecular helicity according to an enantiomerization process entailing a one-ring flip pathway with ΔG⧧ = 5.9 kcal mol-1 and a two-ring flip pathway with ΔG⧧ = 13.8 kcal mol-1. On the contrary the Z- and E-isomers of mesityl phenyl sulfine (MesPhCSO) adopt essentially achiral conformations (Cs symmetry), having the Ph−CSO rotation barriers equal to 5.2 and 5.8 kcal mol-1, respectively, and the mesityl−CSO rotation barriers equal to 21.3 and 15.1 kcal mol-1, respectively.

Thioacylsilanes containing the ferrocene moiety, easily prepared from the corresponding acylsilanes with Lawesson's reagent at room temperature, can be transformed into vinyl silanes, sulfur heterocycles and sulfines.

The allylation of acylsilanes with tetraallyltin in the presence of catalytic amounts of Sc(OTf) 3 proceeded smoothly to afford the silylated homoallylic alcohols in good yields. Subsequent protiodesilylation gave the formal adducts of the corresponding aldehydes. The homochiral acylsilane 11 gave a reversal of asymmetric induction in the Sc(OTf) 3 catalyzed allylation and in the Sakurai reaction.

Cyclic and open chain α-silyl vinyl sulfides, obtained from thioacylsilanes, react with acid chlorides in the presence of Lewis acid to give thioannulated cyclopentenones and thiofunctionalized enones. The effect of the substituents at silicon on these reactions has been investigated.

A detailed investigation of the desilylation of (Z)-α-dimethylphenylsilyl vinyl sulfides with fluoride ion has shown that in substrates containing an electron-withdrawing group β to the sulfur, phenyl group migration occurs as a result of a fluoride ion catalyzed retro-Michael reaction.

ω-Haloacylsilanes 1 were selectively transformed via thioacylsilanes into Z-silyl-enethiols 4 with solid sodium hydrogen carbonate or into 2-silylthiacycloalk-2-enes 5 of common to large ring size with solid sodium hydroxide. Compounds 5 underwent protiodesilylation.

endo - and exo -trimethylsilyl-3-phenyl-2-thiabicyclo[2.2.1]hept-5-enes, the endo -trimethylsilyl- exo -S-oxide and their S,S-dioxide derivatives were protiodesilylated with fluoride ion. Stereoconvergent reactions were found, affording the endo -phenyl derivatives. These results can be rationalised with the hypothesis of a common carbanionic intermediate. In contrast, the desilylation of 3- endo -trimethylsilyl-3- exo -phenyl-2-thiabicyclo[2.2.1]heptane gave a mixture of endo - and exo -isomers, thus proving the involvement of the double bond in the control of the reaction stereoselectivity.

Aliphatic silyl thioketones containing an α-hydrogen atom undergo enethiolization to Z-α-silyl enethiols 2. Compounds 2 react with a variety of halides R3X to give open-chain α-silyl vinyl sulfides 3. Protiodesilylation of 3 was achieved upon treatment with fluoride ion to give vinyl sulfides 4. Reaction of 3 with Grignard reagents, in the presence of an appropriate nickel catalyst, results in a series of vinylsilanes 5 with a specific geometry.

Thiono-ester S-oxides, a rather neglected class of sulfines, can be readily obtained by nucleophilic substitution of chlorine in chlorosulfines by sterically demanding phenolates and alcoholates. The reaction occurs with predominant retention of the configuration of the starting chlorosulfine.

Reaction of dithioesters and trithiocarbonates with silylated nucleophiles under fluoride ion conditions affords a novel example of silyl mediated regiochemical control in the thiophilic functionalization.

The 17O NMR shift values δo of 20 sulfinylamines R–NSO 2 and of 14 sulfines RR′CSO 3(R and R′ mostly arene groups) were compared with those of the isoelectronic SO21. They show δo at much lower field than practically all other classes of S–O compounds; at the same time they exhibit the high substituent sensitivity which is typical for true πp bond systems, and absent in S+–O– compounds. The difference is discussed in terms of bond order and electronic excitation energy. Comparison of the E- and Z isomers of O-methyldiaryl sulfines yields the conformation of these compounds: one arene ring is (nearly) coplanar with the CSO group and the other (nearly) perpendicular to it. This demonstration for the molecules in solution is supported by an X-Ray structure determination.

The reaction of acylsilanes 1 with Grignard reagents gives the diastereomeric α-hydroxysilanes 3 . The level of asymmetric induction depends on the nature of R 1 and R 2 . Good results were obtained for R 1 =t-Bu, R 2 =Me and R 1 =α-Napht, R 2 =Ph. Subsequent desilylation occurs with predominant inversion of configuration at carbon.

Photo-induced cycloadditions of phenyl triphenylsilyl thioketone 1 with electron-poor olefins (acrylonitrile, methyl acrylate and cis- and trans-1,2-dichloroethene) gave silyl thietanes in a regio- and highly stereo-selective manner. In contrast, reaction with vinyl ethers gave thietanes without any regio- or stereo-control. Reaction with α-methylstyrene and 2,3-dimethylbut-2-ene gave open chain products. Desilylation of silyl thietanes occurs with prevalent inversion of configuration at the carbon bearing the silicon group.

ω-Haloacylsilanes 1 were selectively transformed via thioacylsilanes into Z-silyl-enethiols 4 with solid sodium hydrogen carbonate or into 2-silylthiacycloalk-2-enes 5 of common to large ring size with solid sodium hydroxide. Compounds 5 underwent protiodesilylation.

The palladium-catalyzed desilylation−arylation of substituted vinylsilanes by p-iodoanisole in the presence of bidentate phosphine ligands is described. Apart from enhancing the rate of the reaction considerably, heteroatom-based functional groups in the vinylsilane moiety have a profound influence on the regiochemistry. A catalytic cycle for the chelation-controlled desilylation−arylation reaction involving five- and six-membered chelate rings is proposed.

Treatment of methyl 1-methylsulfanylvinyl sulfoxides with sodium thiophenolate in MeOH gives 1-methylsulfanylalk-1-en-3-ols.

Structural variations in acylsilane molecules allow a number of new selective synthetic processes to be performed which lead to sulfur-containing heterocycles, highly functionalized and unsaturated polycarbonyl derivatives, polyenes, and β - and γ -aminoalcohols. The synthesis of these compounds, most of them not easily accessible through conventional routes, takes advantage of the site-selective reactions occurring at the C–Si bonds, of the increased stability of acylsilanes with respect to that of the corresponding aldehydes and of the high diastereofacial selectivity introduced by the SiR 3 group. Herein we report the different synthetic strategies leading to the synthesis of several functionalized acylsilanes and their synthetic applications. The use of new selective polymetallic reagents for the nucleophilic silylation will be presented as well.

The allylation of acylsilanes with tetraallyltin in the presence of catalytic amounts of Sc(OTf) 3 proceeded smoothly to afford the silylated homoallylic alcohols in good yields. Subsequent protiodesilylation gave the formal adducts of the corresponding aldehydes. The homochiral acylsilane 11 gave a reversal of asymmetric induction in the Sc(OTf) 3 catalyzed allylation and in the Sakurai reaction.

The new allylaminosilanes 2a – c , derived from chiral amines, react with benzaldehyde and pivalaldehyde in the presence of SnCl 4 to give homoallylic alcohols 4a – b with enantiomeric excesses of up to 30%.

A practical route is described for the synthesis of enantiopure β- and γ-amino alcohols with two stereocenters, starting from homochiral α- (1 and 5) and β- (13 and 16) -aminoacylsilanes, and involving stereoselective addition of allylmetal compounds and subsequent stereospecific protiodesilylation of the adducts. The degree of diastereoselectivity achieved in the nucleophilic addition step depends on both the nitrogen-protecting group and the reagents used. Diastereomeric excess (de) values equal to or higher than 98% were obtained in the TiCl4-promoted allylation of the N-Pht-aminoacylsilanes 1 and 13 and of the N-Ts-aminoacylsilane 5 with allyltrimethylsilane. Lower de values were obtained in the Sc(OTf)3-catalyzed allylation of 5 with tetraallyltin and in the additions of both allyltrimethylsilane and tetraallyltin to the N-Ts-β-aminoacylsilane 16. Protiodesilylation of the adducts, leading to the β- and γ-amino alcohols, was accomplished with TBAF, except in the case of the adducts obtained from 5. For these, a preliminary removal of the tosyl group was necessary, which was accomplished with simultaneous desilylation by treatment with Na in liquid ammonia.

Thioacylsilanes containing the ferrocene moiety, easily prepared from the corresponding acylsilanes with Lawesson's reagent at room temperature, can be transformed into vinyl silanes, sulfur heterocycles and sulfines.