Study of the reaction of 1,1-bis(trimethylsilyl)-2-phenylethylene with some acyl chlorides in the presence of AlCl3

1,1-Bis(trimethylsilyl)-2-phenylethylene (1), which has been synthesized from the Peterson reaction between (Me₃Si)₃CLi and benzaldehyde, reacts with various acyl chlorides (RCOCl, R = Me, Et, iso-Pr, n-Bu, iso-Bu, iso-C₅H₁₁, PhCH₂, PhCH₂CH₂) in the presence of AlCl₃ to give -silyl-,β-unsaturated enones 3a–3h with high E stereoselectivity along with trans-,β-unsaturated ketones 4a–4h. The enones 3 can be partially converted into the ketones 4 with an excess of AlCl₃. Reaction of 1 with RCOCl, (R = Ph, CH₃CH=CH) afforded only the ketones 4. Yields were dependent on time and the amounts of AlCl₃ used.     

Silyl stabilized azanes: Reactions of mono- and dilithium bis(trimethylsilyl)hydrazide with dichloro- and tetrachlorostannane

SnCl₄ acts primarily as an oxidant and oxidizes monolithium bis(trimethylsilyl) hydrazide 1 to mainly bis(trimethylsilyl)amine, BSA and tris(trimethylsilyl)hydrazine, TrSH and itself get reduced to SnCl₂. Similarly, reaction of SnCl₄ with dilithiumbis(trimethylsilyl) hydrazide 2, oxidizes it to lithium tris(trimethylsilyl)hydrazide, Li-TrSH. Reaction of dichlorostannane (reduction of oxidation state of tin from +4 to +2) with 1 gives a simple substitution reaction and give a pale yellow solid, 1,4-bis(trimethylsilyl)-1,2,4,5-tetraza-3,6-distannacyclohexane, 3b. Whereas, in reaction of 2 with SnCl₂ intermediate stannimine [(Me₃Si)₂N-NSn], tetramerizes and further loses tetrakis(trimethylsilyl)tetrazene, TST to give a cubane compound [(Me₃Si)N-Sn]₄, 4.     

Synthesis of new α-aminonitriles containing organosilicon groups via three component Strecker reactions

A three-component efficient procedure is described for the synthesis of α-aminonitriles containing bis(trimethylsilyl)ethenyl groups from 4-[2,2-bis(trimethylsilyl)ethenyl]benzaldehyde (1), aromatic amines and trimethylsilyl cyanide (TMSCN). Reactions have been studied in the presence of various Lewis acids as catalysts or in ionic liquids under mild conditions. Compound (1) was obtained via Peterson olefination of terephthaldehyde with tris(trimethylsilyl)methyllithium, (Me₃Si)₃CLi, in THF at 0 °C.     

A palladium catalyzed atom-efficient cross-coupling reactivity of triarylbismuths with α,β-unsaturated acyl chlorides

An atom-efficient cross-coupling reactivity of triarylbismuths (1 equiv) was demonstrated by cross-coupling reaction with 3 equiv of α,β-unsaturated acyl chlorides under palladium catalysis in the synthesis of a series of functionalized α, β-unsaturated ketones in high isolated yields.     

α-Bromo-β,γ-unsaturated ketenes for the synthesis of α-benzylamino-β,γ-unsaturated acids

The synthesis of α-benzylamino-β,γ-unsaturated acids has been developed starting from α-bromo-α,β-unsaturated chlorides. Via treatment of the acyl chlorides with (R)-pantolactone in the presence of TEA, the in situ formation of the deconjugated ketenes and their direct transformation into chiral esters was performed. The substitution of bromine with benzylamine, followed by acid hydrolysis, allowed to us obtain enantiomerically enriched α-benzylamino-β,γ-unsaturated acids.     

Synthesis of new imines and amines containing organosilicon groups

The Peterson olefination reaction of terephthalaldehyde with tris(trimethylsilyl)methyl lithium, (Me₃Si)₃CLi, in THF at 0 °C gives 4-[2,2-bis(trimethylsilyl)ethenyl]benzaldehyde (1) and 4,4-bis[2,2-bis(trimethylsilyl)ethenyl]benzene (2). The new aldehyde (1) reacts with variety of amines in ethanol to afford the corresponding imines (3) containing vinylbis(trimethylsilyl) group. The newly synthesized imines (3) can be completely converted into amines containing vinylbis(trimethylsilyl) group with an excess amount of NaBH₄. In the case of N-[4-(2,2-bis(trimethylsilyl)ethenyl)benzyl]-2,6-dimethylaniline LiAlH₄ was used as a reducing agent in THF.     

Elimination of bis(trimethylsilyl)stannylene from tris(trimethylsilyl)stannylated zirconocene and hafnocene chlorides

Reactions of (Me₃Si)₃SnK with Cp₂MCl₂ (M = Zr, Hf) give the respective stannylated metallocene chlorides. These complexes display a tendency to eliminate bis(trimethylsilyl)-stannylene under Cp₂M(Cl)SiMe₃ formation.     

Reinvestigation of the synthetic and mechanistic aspects of Mn(III) acetate mediated oxidation of enones

Mn(OAc)₃ mediated α′-acetoxylation of α,β-unsaturated enones is reinvestigated from a synthetic and mechanistic point of view and an improved procedure based on the use of acetic acid as a co-solvent is presented. Excellent results were obtained for a variety of structurally diverse and synthetically important enones under the optimized conditions.     

Catalytic asymmetric Michael reactions of dibenzyl malonate to α,β-unsaturated N-acylpyrroles using a La(O-iPr)3/Ph-linked-BINOL complex

Catalytic asymmetric Michael reactions of a malonate to acyclic α,β-unsaturated N-acylpyrroles as ester equivalent acceptors are described. A La(O-iPr)₃/(S,S)-linked-BINOL complex, which is suitable for Michael addition to cyclic enones, is not suitable for acyclic α,β-unsaturated N-acylpyrroles. A new (S,S)-Ph-linked-BINOL chiral ligand was developed to improve enantioselectivity, and a La(O-iPr)₃/(S,S)-Ph-linked-BINOL complex with the addition of HFIP afforded Michael adducts in good yield and enantioselectivity (up to 96% ee).     

Palladium-catalyzed cross-coupling reaction of bis(pinacolato)diboron with vinyl triflates β-substituted by a carbonyl group: efficient synthesis of β-boryl-α,β-unsaturated carbonyl compounds and their synthetic utility

Cross-coupling reaction of bis(pinacolato)diboron with β-(trifluoromethanesulfonyloxy)-α,β-unsaturated carbonyl compounds was carried out in the presence of PdCl₂(PPh₃)₂-2PPh₃ (3 mol%) and KOPh in toluene or K₂CO₃ in dioxane for the synthesis of cyclic and acyclic β-boryl-α,β-unsaturated esters, amides, and ketones in high yields. The vinylboronates thus obtained readily participated in carboncarbon bond formation such as cross-coupling with vinyl triflates and 1,4-addition to α,β-unsaturated ketones.     

Reactivite des carbanions benzyliques : VI. Structure et reactivite du trimethylsilyl-9 dihydro-9,10 anthracene; preparation des bis(trimethylsilyl)-9,9 et trimethylsilyl-9 alkyl-9 dihydro-9,10 anthracenes

The structure of 9-trimethylsilyl-9,10-dihydroanthracene (Me₃SiDHA) has been studied by NMR; the coupling constants of the three 9,10 protons do not change at between 25 and 90°C (ABM spectrum; J_AB }- 18.2; J_AM ? 1.2; J_BM ? 0.3 Hz in toluene-d₈), indicating that the Me₃Si group prefers the quasi axial position. In the presence of BuLi in THF, Me₃SiDHA reacts with Me₃SiCl to yield three new products: 9,9-bis(trimethylsilyl)-9,10-dihydroanthracene (IId) (major), (9,10-dihydroanthracen-9-yl)dimethylsilyl(trimethylsilyl)methane (V) and (9-trimethylsilyl-9,10-dihydroanthracen-9-yl)dimethylsilyl(trimethylsilyl)-methane (VI) together with the known 9,10-bis(trimethylsilyl)-9,10-dihydroanthracene (cis and trans). The carbanion of Me₃SiDHA can also be alkylated (alkyl  Me, Et, i-Pr) to the new 9,9-disubstituted derivatives: 9-Me₃Si-9-alkyl-DHA.The formation of the carbanion of Me₃SiDHA has been investigated and reveals a competition in the abstraction by the base of H₉ and H₁₀; the latter is less crowded but the 9-carbanion is stabilized by the vicinity of the silicon atom. The carbanion obtained from Me₃SiDHA reacts exclusively at C(9) with D₂O. A study of the alkylation of 9-trimethylsilyl-9-deuterio-9,10-dihydroanthracene shows that the generation of the 10-carbanion is followed by a 1,4 hydrogen rearrangement which yields the 9-carbanion. The mechanism is discussed and the roles of Me₃Si and t-Bu are compared in the DHA series.     

Synthesis of 1,1-bis(silyl)-1-alkene derivatives bearing Si-H functional groups via Peterson protocol

Various aromatic aldehydes were converted to one-carbon elongate 1,1-bis(silyl)-1-alkene derivatives bearing Si-H functional and reactive groups in a convenient one-pot operation via the Peterson protocol. Then poly(styrene) and poly(α-methylstyrene) (?&II) random homopolymers were synthesized by solution free radical polymerization at 70(±1) °C using α,α′-azobis(isobutyronitrile) (AIBN) as an initiator. The aldehyde group is introduced by direct electrophilic substitution of polymers ? and II. This formylation reaction was conducted in two different solvents: dichloromethane (CH₂Cl₂) and nitrobenzene (PhNO₂). The results indicate that PhNO₂ appeared to be a more suitable solvent for such an aldehyde functionalization of the polymers. The formylated polymers (I_CHO, II_CHO) were then converted to Si-H functionalized polymers (I_Si-H, II_Si-H) via reaction with tris(dimethylsilyl)methyllithium, (HMe₂Si)₃CLi.     

Synthesis and reactions of p-vinylbenzyltris(trimethylsilyl)methane

Benzyl chloride was treated with (Me₃Si)₃CLi to give (Me₃Si)₃CCH₂Ph (1). A new styrene derivative, (Me₃Si)₃CCH₂C₆H₄(CHCH₂-p) (2), was synthesized by reaction of p-vinylbenzyl chloride with (Me₃Si)₃CLi in the presence of CuCl. Addition and oxidation reactions on 2 gave a series of new compounds (Me₃Si)₃CCH₂C₆H₄X-p (X = CH₂CH₃, CHBrCH₂Br, CHClCH₂I, CHBrCH₂I, cyclo-C₃H₃Cl₂, CHOHCH₂OH, COOH, CH₂OH).     

Metallorganische diazoalkane : XVI. Synthese von silyldiazoalkanen Me3Si(LnM)CN2

Silyldiazoalkanes Me₃Si(L_nM)CN₂ (L_nM = Me₃Si, Me₃Ge, Me₃Sn, Me₃Pb; Me₃As, Me₃Sb, Me₃Bi) have been synthesized by three different routes: (a) reactions of the Me₃SiCHN₂ with metal amides L_nMNR¹R² of Group IVB and VB elements, using Me₃SnCl as catalyst; (b) reactions of the in situ prepared organolithium compound Me₃SiC(Li)N₂ with organometallic chlorides Me₃MCl (M = Si, Ge); (c) tincarbon bond cleavage reaction of (Me₃Sn)₂CN₂ with Me₃SiN₃, affording Me₃SnN₃, traces of bis(trimethylsilyl)diazomethane (Me₃Si)CN₂, trimethylsilyl(trimethylstannyl)diazomethane Me₃Si(Me₃Sn)CN₂ and bis(trimethylsilyl)aminoisocyanide (Me₃Si)₂NNC as the major reaction products. IR and NMR data (¹H, ¹³C, ²⁹Si, ¹¹⁹Sn, ²⁰⁷Pb) of the new heterometal-diazoalkanes are reported and discussed in comparison to relevant compounds of the organometallic diazoalkane series.     

Tris(dimethylsilyl)methyllithium: A Reagent for the Synthesis of Vinylbis(silanes) Containing Si–H Functional Groups

Reactions between a series of nonenolisable aldehydes and tris(dimethylsilyl)methyllithium, (HMe₂Si)₃CLi, are described. The Peterson reaction takes place readily to give vinylbis(silanes). Moreover, styrene and butyl acrylate 1:1 copolymer (P), prepared by use of α,α′-azobis(isobutyronitrile) (AIBN) as an initiator in toluene at 70 ± 1°C, was formylated via direct electophilic substitution by methyl dichloromethyl ether (Cl₂CHOMe) in the presence of tin(IV) chloride (SnCl₄) in nitrobenzene (PhNO₂) as solvent. The reaction of (HMe₂Si)₃CLi with formyl groups on the side chains of the copolymer led to new macromolecules bearing vinylbis(silane) functional groups.     

A convenient method for the synthesis of (Z)-α-haloacrylates: Lewis base-catalyzed carbonyl olefination using α-halo-C,O-bis(trimethylsilyl)ketene acetals

A highly useful method for the stereoselective synthesis of (Z)-α-haloacrylates from various aldehydes that uses α-halogenated ethyl-C,O-bis(trimethylsilyl)ketene acetals in the presence of a Lewis base catalyst such as acetate salts was established. This procedure gives the corresponding α-halo-α,β-unsaturated esters in high yields with excellent stereoselectivity from E/Z mixtures of ketene silyl acetals under mild conditions.     

Lewis acid-promoted reaction of β,γ-unsaturated α,α-dimethoxy esters with silyl nucleophiles

The Lewis acid-promoted reaction of β,γ-unsaturated α,α-dimethoxy esters, which are easily prepared by the acetalization of β,γ-unsaturated α-keto esters, with silyl nucleophiles is presented. By employing trimethylsilyl enolate and allyltrimethylsilane as nucleophiles, the BF₃-promoted reactions of a series of β,γ-unsaturated α,α-dimethoxy esters bearing aromatic and aliphatic substituents proceeded at the γ-position in an SN2′ manner to furnish γ-substituted α,β-unsaturated α-methoxy esters in good yields with high regioselectivity. In contrast, the reaction using trimethylsilyl cyanide predominantly occurred at the α-position, and the reaction of silyl hydride resulted in a mixture of α- and γ-regioisomers in favor of the γ-substitution products.     

A new method for the preparation of α-(perfluoroalkyl) carbonyl and γ-(perfluoroalkyl)-α,β-unsaturated carbonyl compounds

R_fI(Ph)OSO₂CF₃ or R_fI(Ph)OSO₃H smoothly reacted with various trimethylsilyl enol ethers under mild conditions to give α-(perfluoroalkyl) carbonyl and γ=(perfluoroalkyl)-α,β-unsaturated carbonyl compounds in high yields.     

Effect of substituents on addition polymerization of norbornene derivatives with two Me3Si-groups using Ni(II)/MAO catalyst

Addition polymerization and copolymerization of bis(Me₃Si)-substituted norbornene-type monomers such as 5,5-bis(trimethylsilyl)norbornene-2, 2,3-bis(trimethylsilyl)norbornadiene-2,5 and 3,4-bis(trimethylsilyl)tricyclo[4.2.1.0^2,5]nonene-7, in the presence of Ni(II) naphtenate/MAO catalyst were studied. Disubstituted norbornene and norbornadiene were found to be practically inactive in homopolymerization. On the other hand, their copolymerization with norbornene proceeded with moderate yields of copolymers containing predominantly norbornene units. Under studied reaction conditions 2,3-bis(trimethylsilyl)norbornadiene-2,5 was transformed into the only exo-trans-exo-dimer as a result of the [2+2]-cyclodimerization reaction. Moving Me₃Si-substituents one carbon atom away from norbornene double bond made 3,4-bis(trimethylsilyl)tricyclo[4.2.1.0^2,5]nonene-7 active in homopolymerization and allowed to obtain addition homo-polymer with two Me₃Si-substituents in each elementary unit. The reaction mechanism and steric effect of Me₃Si-substituents are also discussed.     

Development of effective Lewis acids for the catalytic Diels-Alder reaction of α,β-unsaturated lactones with cyclopentadiene

We found that ‘Tf₂CH₂ + Me₃Al’ systems are effective catalytic systems for the DA reaction of less reactive α,β-unsaturated lactone derivatives, compared to α,β-unsaturated ester derivatives, with cyclopentadiene. Mononuclear aluminum methide complex, Tf₂CHAlMe₂, as an active species is formed in these catalytic systems. Effects of lactone ring-size on the reactivity and stereoselectivity were also examined. By expanding ring-size, reactivity of α,β-unsaturated lactones reduced but endo-selectivity notably increased.