Highly useful carbon-carbon bond forming reactions using stable allenyl, propargyl, or allyl- propargyl hybrid cations have been developed. These carbocations could be generated from silyl 1-(π-donor)-substituted propargyl ethers by the action of trimethylsilyl trifluoromethanesulfonate in dichloromethane at-78° C to room temperature and could be attacked nucleophilically by electron rich arenes, allylsilanes, or enol silyl ethers, giving ...