Direct dilithiation with n-BuLi/TMEDA gave, after reaction with TMS chloride, the 2,4-disilyl derivative in 85-95% yield: J. Org. Chem., 49, 4657 (1984). Has been used as the non-transferable group in the conjugate addition of organocuprates. (With Li dialkyl cuprates only one of the two alkyl groups is transferred, with consequent 50% maximum yield.): Chem. Lett., 745 (1988).