The addition of different substituted allylsilanes 2 to unactivated alkynes 1 in the presence of catalytic mounts of HfCl4 or the EtAlCl2- TMSC1 catalyst system produced in high yields the silylated 1,4-dienes 3 regio- and stereoselectively. The exclusive trans manner of addition was confirmed by analysis of crude reaction mixtures by 1H NMR and capillary GLC methods. Good agreement of relative reactivities of reaction of various allylsilanes 2a-e toward phenylacetylene (1a) in the presence of HfCl4 with the relative reaction rates of 2a-e with carbenium ions supported the involvement of cationic species 11 as a reaction intermediate. The mechanisms for the HfCl4 and EtAlCl2-TMS catalyzed trans-allylsilylation of alkynes are proposed.
ASJC Scopus subject areas
- Colloid and Surface Chemistry