Kronenether-funktionalisierte Carbosilandendrimere

The synthesis of the allyloxymethyl-functionalized crown ethers of type CH₂CHCH₂OCH₂15-crown-5] (3a) and CH₂CHCH₂OCH₂18-crown-6] (3b) can be achieved by treatment of HOCH₂15-crown-5] (1a) and HOCH₂18-crown-6] (1b) with CH₂CHCH₂Br (2) in presence of KOH. The hydrosilylation of 3a and 3b with Si(CH₂CH₂CH₂SiMe₂H)₄ (4) and Si(CH₂CH₂CH₂SiMe(CH₂CH₂CH₂SiMe₂H)₂)₄ (6) in presence of the Karstedt catalyst affords the respective crown ether end-capped carbosilane dendrimers Si(CH₂CH₂CH₂SiMe₂CH₂CH₂CH₂OCH₂15-crown-5])₄ (5a), Si(CH₂CH₂CH₂SiMe₂CH₂CH₂CH₂OCH₂18-crown-6])₄ (5b), Si(CH₂CH₂CH₂SiMe(CH₂CH₂CH₂SiMe₂CH₂CH₂CH₂OCH₂15-crown-5])₂)₄ (7a) and Si(CH₂CH₂CH₂SiMe(CH₂CH₂CH₂SiMe₂CH₂CH₂CH₂OCH₂18-crown-6])₂)₄ (7b). The latter dendrimers are obtained in almost quantitative yield. The complexation behaviour of 5 and 7 towards different alkali metal cations is discussed.