Pentacoordinate silicon intermediates in relay substitution reactions of organosilanes: successive nucleophilic attack at silicon and its adjacent carbon

Synthesis of a 35-Member Stereoisomer Library of Bistramide A: Evaluation of Effects on actin State, Cell Cycle and Tumor Cell Growth

“…43 Alternatively, formation of a pentacoordinated silicon followed by 1,2-migration was also postulated. 45 Lastly, X-ray crystal structure 46 and gas phase and theoretical studies 47 showed the α C-O bond (adjacent to the Si) to be longer and weaker than the β C-O bond. Our particular system has the added advantage of a Lewis basic site on the adjacent carbonyl to aid in opening via coordination of resident metal centers.…”

“…Fortunately, addition of the alkyne to the β-carbon of the silicon functionality was not detected in the described conditions. Several explanations have been put forth on the selective opening of epoxysilanes. ,− One interesting hypothesis includes the formation of a pentacoordinated silicon followed by 1,2-migration, though more recent studies with allyl cuprates do not support this pathway . Alternatively, prior coordination of nucleophile with both the R-carbon and silicon functionality has also been postulated .…”

Synthesis and unusual rearrangement of 2-organyl-4,4,6,6-tetramethyl-5-chloro-6λ5-sila-Δ2-dihydro-1,3,4λ4-oxadiazinium chlorides

“…The proposed 1,2-sigmatropic shift resembles the well-known fluorine-induced relay of the nucleophile from silicon to its adjacent carbon in thermodynamically controlled reactions of the nucleophilic substitution of ClSiMe 2 CH 2 Cl with PhEH (E = O or NMe). 7 A more detailed study of compounds 3 is in progress.…”

Ring-Opening Reactions of α,β-Epoxy Silanes with Organocopper Reagents: Reaction at Carbon or Silicon?

“…Both the reactivity of Me 3 SiCH 2 X 20c and the α-opening of α,β-epoxy silanes 6ad,8a,12bc,13c,21 have been rationalized by assuming initial coordination of the nucleophile with both silicon and carbon. Coordination of the nucleophile with silicon followed by 1,2-rearrangement to the α-carbon 6d,12b,21b, has also been suggested for the α-opening reactions. , …”