Lithium methoxide transition state

Calculational results also support a transition state formed from the six-membered Lewis salt (50). As calculated at the 3-21G level the transition state for the reaction of lithium methoxide with formaldehyde... 

A detailed study by Westaway and Waszczylo61 used chlorine leaving group and secondary a-deuterium KIEs along with Hammett p values and activation parameters to demonstrate how the transition state is altered when a substituent on the benzene ring in the substrate is varied in the Sn2 reactions between para-substituted benzyl chlorides and thiophenoxide ions in 0.25 N lithium methoxide in methanol at 25°C (Equation (18)). 

Transition metal-free hydrosilylation of carbonyl compounds can be realized with the use of Brpnsted or Lewis acids as well as Lewis bases. Alkali or ammonium fiuorides (CsF, KF, TBAF, and TSAF) are highly effective catalysts for the reduction of aldehydes, ketones, esters, and carboxylic acids with H2SiPh2 or PMHS. Lithium methoxide promotes reduction of esters and ketones with trimethoxysilane. A generally accepted mechanism of Lewis base-catalyzed hydrosilylation of carbonyl compovmds involves the coordination of the nucleophile to the silicon atom to give a more reactive pentacoordinate species that is attacked by the carbonyl compound giving hexacoordinate silicon intermediates (or transition states), in which the hydride transfer takes place (Scheme 30) (235). 

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