10.1021/jo501888r.s001 Sukesh Shekar Sukesh Shekar Seth N. Brown Seth N. Brown Mechanism and Selectivity of Methyl and Phenyl Migrations in Hypervalent Silylated Iminoquinones American Chemical Society 2014 isomer ONOQ phenyl migration CH DFT calculations Phenyl Migrations PhSiMeCl 2 methyl groups R group 2014-12-19 00:00:00 Journal contribution https://acs.figshare.com/articles/journal_contribution/Mechanism_and_Selectivity_of_Methyl_and_Phenyl_Migrations_in_Hypervalent_Silylated_Iminoquinones/2223700 Chlorosilanes R­(X)­(Y)­SiCl (R = Me, Ph; X, Y = Me, Ph, Cl) have been reported to react with Pb­(ONO<sup>Q</sup>)<sub>2</sub> (ONO<sup>Q</sup> = 3,5-di-<i>tert</i>-butyl-1,2-quinone-(3,5-di-<i>tert</i>-butyl-2-oxy-1-phenyl)­imine) to give five-coordinate (X)­(Y)­Si­(ON­[R]­O), in which the R group has migrated from silicon to nitrogen. This migration is intramolecular, as confirmed by the lack of crossover between (CH<sub>3</sub>)<sub>3</sub>SiCl and (CD<sub>3</sub>)<sub>3</sub>SiCl in their reaction with Pb­(ONO<sup>Q</sup>)<sub>2</sub>. Reaction of PhSiMeCl<sub>2</sub> takes place with high kinetic stereoselectivity to produce isomer Ph­(Cl)­Si­(ON­[Me]­O) in which the phenyl is axial in the trigonal bipyramid, which subsequently isomerizes to the thermodynamic isomer with axial chlorine. This indicates that migration takes place preferentially from the stereoisomer of the octahedral intermediate, κ<sup>3</sup>-Ph­(CH<sub>3</sub>)­(Cl)­Si­(ONO<sup>Q</sup>), in which the phenyl and methyl groups are mutually trans, indicating that the observed complete selectivity for methyl over phenyl migration is due to intrinsic differences in migratory aptitude. DFT calculations suggest that migration takes place from this isomer not because it undergoes migration faster than other possible stereoisomers, but because it is formed most rapidly, and migration occurs faster than isomerization.