H. Westmijze

Stabilization of organosilver(I) compounds, and their application in organic synthesis

The favourable influence of lithium bromide on the thermal stability of organosilver(I) compounds is described. The stabilized silver(I) compounds have been brought into reaction with conjugated enynes; the regiochemistry of the reactions appears to depend on steric factors. A comparison is presented of the behaviour of the silver(I) and the corresponding copper(I) reagents in this reaction.

Regio- and stereo-chemical features of the stannylcopper(I)-induced substitution in propargylic substrates

Abstract Stannylcopper(I) species, R 3 SnCu and [R 3 Sn] 2 CuLi, preferentially convert propargylic substrates, R 1 Cue5fcCCR 2 R 3 X (X = Br, MeCO 2 , MeS(O)O or MeSO 3 ) into allenes R 3 Sn(R 1 )Cue5fbCue5fbCR 2 R 3 . Only when the group R 1 causes much greater steric hindrance than with R 2 and R 3 is the acetylenic product R 1 Cue5fcCCR 2 SnR 3 formed. The stereochemical course of the allene formation has been studied in both the steroid and non-steroid series, and found to be mainly or exclusively anti.

Application of allenylsilver(I) compounds in organic synthesis. A simple route to substituted allenes

Allenylsilver(I) compounds, prepared in situ by addition of alkylsilver(I)-lithium bromide complexes to butenynes, readily react with a variety of electrophiles. The produced compounds are usually almost pure allenes, but in some cases substantial amounts of the isomeric acetylenes are also formed.

Convenient synthesis of (triphenyl)germyl and (triphenydstannyl substituted allenes

Allenyl-germanes and -stannanes, Ph3MC(R)ue5fbCue5fbCR′R″ (M = Ge, Sn) can be obtained, generally in excellent yield, through alkylcopper(I)-induced 1,3-substitution of the propargylic chlorides Ph3MCue5fcCCR′R″Cl. In the tin series, however transmetallation is the main process when MeCu, H2Cue5fbCHCu or PhCu are used. The allenyl compounds in which R is (trimethylsilyl)ethynyl or 4,4-dimethyl-1,2-pentadienyl can be obtained by using the organozinc compounds instead of the copper(I) compound and using tetrakis(triphenylphosphine)palladium as catalyst.

Organocopper(I) mediated synthesis of 1-alkenylsilanes and 1,3-alkadienylsilanes from ethynylsilanes

Abstract Ethynylsilanes (I) are converted into α-silyl substituted (Z)-alkenylcopper(I) compounds (II) by treatment with RCu reagents. The adducts II react with a variety of electrophiles to give the 1-alkenylsilanes RCHue5fbC(E)SiR 3 ′ (III: E = H, Cl, Br, I, CN, SnMe 3 , SMe, Me, H 2 CHCH 2 ). The conversion of I into III (E = H) can also be effected by using homocuprates, R 2 CuMgCl, and triorganodicuprates, R 3 Cu 2 MgCl. The latter reagent should be used when the group R is methyl. An interesting 1,3-diene formation is observed on treating excess of ethynyltrimethylsilane (Ib) with R 3 Cu 2 MgCl; this reaction involves addition of intermediary vinylcuprates to unreacted 1-alkynylsilane (Ib). The intermediary 1,3-dienyl adduct (VIIb) reacts with various electrophiles to give 1,3-dienes, RCHue5fbC(SiMe 3 )CHue5fbC(E)SiMe 3 (VIIIb).

Organosilver(I) chemistry: On the reaction of RAg and R2AgMgCl compounds with conjugated enynenitriles

Abstract The addition of RAg and R 2 AgMgCl to enynenitriles is described. RAg reagents prefer to transfer their R group to the double bond of these nitriles, so that after protolysis 2,3-alkadienenitriles are obtained, while the homoargentates generally give 2,4-alkadienenitriles. The regio- and stereo-chemical course of the reactions are compared with those in additions of RCu and R 2 CuMgCl to the enynenitriles.

Regiospecific addition of alkylsilver species to enynyl sulfides, -sulfoxides, and -phosphines

The allenes RCH2(R′)ue5fbCue5fbCHX (X ue5fb SMe, S(O)Me or PPh2; R′ ue5fb H or Me) are formed regiospecifically by reaction of alkylsilver species with the enynes H2Cue5fbC(R′)Cue5fcCX.