Leaving Group Effects on the Selectivity of the Silylation of Alcohols: The Reactivity–Selectivity Principle Revisited

Abstract

TBS protection of primary alcohol naphthalen-1-ylmethanol (4a) and secondary alcohol 1-(naphthalen-1-yl)ethanol (4b) has been studied under various reaction conditions. The primary/secondary selectivity is largest in the comparatively slow Lewis base catalyzed silylation in apolar solvents and systematically lower in DMF. Lowest selectivities (and fastest reaction rates) are found for TBS triflate 1b, where only minor effects of solvent polarity or Lewis base catalysis can be observed.

Size-dependent rate acceleration in the silylation of secondary alcohols: the bigger the faster

“…This is in full agreement with experimental results showing basically no turnover between TBDMSCl ( 2b ) and secondary alcohols in the absence of the auxiliary base. 39 , 40 Reaction energies become more favourable and eventually also negative on increasing the size of the silyl chloride reagent. Interestingly, the tert -butyldimethylsilyl ether 5fb is less stable than the trimethylsilyl ether 5fa , most likely due to repulsive steric interactions between the tert -butyl and the pyrenyl substituents.…”

“…The base-catalysed silylation of alcohols is commonly assumed to follow a Lewis base- rather than a general base-catalysed mechanism. 39 – 42 In contrast to acylation reactions, silyl group transfer reactions proceed along an S N 2-like pathway, which implies the relative orientation of catalyst, reagent and substrate shown in the transition state cartoon in Fig. 1b .…”

Crystal structure of 2-((tert-butyldimethylsilyl)oxy)-5-methylisophthalaldehyde, C15H22O3Si

“…Formyl groups can be oxidized to carboxyl groups and reduced to alcohol for further reaction. In addition, tert-butyl dimethylsilyl (TBS) is used as a common protecting group for hydroxyl substituents [13][14][15]. This protecting group can be removed by reaction with a fluoride anion.…”

Synthesis and Characterization of 9‐(Fluoren­‐2‐yl)anthracene Derivatives as Efficient Non‐Doped Blue Emitters for Organic Light‐Emitting Diodes

“…However, these silylating reagents are significantly more hydrolytically unstable and expensive than the corresponding silyl chlorides. Interestingly, the reactions of both TBS‐OTf and TBS‐OClO 3 have recently been shown to be insensitive to Lewis base catalysis 42. The only efficient processes for preparing silyl ethers of tert ‐alcohols with bulky silyl PGs using silyl chlorides that we are aware of are one developed by Nishiguchi using Mg as a promoter [TES‐Cl (3 equiv.…”