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

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

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 RCH=C(E)SiR3′ (III: E = H, Cl, Br, I, CN, SnMe3, SMe, Me, H2CHCH2). The conversion of I into III (E = H) can also be effected by using homocuprates, R2CuMgCl, and triorganodicuprates, R3Cu2MgCl. 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 R3Cu2MgCl; 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, RCH=C(SiMe3)CH=C(E)SiMe3 (VIIIb)

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)=C=CR′R″ (M = Ge, Sn) can be obtained, generally in excellent yield, through alkylcopper(I)-induced 1,3-substitution of the propargylic chlorides Ph3MCCCR′R″Cl. In the tin series, however transmetallation is the main process when MeCu, H2C=CHCu 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