Journal or Book Title
Multiple Pd(O)-catalyzed coupling reactions of9-borabicyclo[3.3.1]nonane (9-BBN) adducts of allylsilanes and bromo benzenes are used to prepare several unusual silametacyclophanes. Reaction of the 9-BBN adduct of dimethyldiallylsilane and 1,3-dibromobenzene gives 4-dimethyl-4-silametacyclophane in 32% yield, while reaction of the 9-BBN adduct of methyltriallylsilane and 1,3,5-tribromobenzene leads to 4-methyl-4-sila[34•10]metacyclophane in 4% yield. NMR data are presented to help characterize these compounds. Computational studies of the cyclophanes HE[-Y-(CH2)n-hCsH3 forE= C, Si, Y = CH2, 0, and n = 2, 3 reveal various important factors in stabilizing compounds with H atE inside the cage. These include that the macrocycle be large enough to accommodate the EH bond and that the EH bond be polarized so that its H atom is positive when directed toward the 1r cloud of the benzene ring. Even the small n = 2 macrocycles are only moderately strained at both E and the benzene base.
American Chemical Society
Kwochka, William R.; Damrauer, Robert; Schmidt, Michael; and Gordon, Mark S., "Synthetic and Computational Studies of Silametacyclophanes: Macrocyclic Cage Compounds" (1994). Chemistry Publications. 267.