The addition of dichlorosilane to both conjugated and unconjugated dienes was studied in the presence of chloroplatinic acid as a catalyst. The mode of addition to conjugated dienes was predominantly by a 1, 4 pathway. With unconjugated dienes, addition to a terminal double bond was much faster than to internal double bonds and hence provided a convenient method for the synthesis of alkenyldichlorosilanes. The latter were cyclized in ...