A Masked Form of an O‐Borylated Breslow Intermediate for the Diastereoselective FLP‐Type Activation of Aldehydes

Abstract

Breslow intermediates are very often elusive species whose application in frustrated Lewis pair (FLP) chemistry is unprecedented. Described herein is the use of a masked form of an O-borylated Breslow (OBB) intermediate that performs FLP-type activation of the carbonyl function of five different benzaldehyde derivatives with complete diastereoselectivity. The resulting compounds are characterised in solution by NMR spectroscopy (compounds 4-8) and in solid state by Xray diffraction analysis (compounds 4-6). A combined kinetic and theoretical investigation reveals the associative nature of the rate determining step and suggests that the OBB intermediate part is never released during the whole process.

(Pyridin‐2‐ylmethyl)triel Derivatives as Masked Frustrated Lewis Pairs. Interactions and CO2‐Sequestration

“…Among the different types of FLP systems, those that show a classical LA/LB pair adduct but present a reactivity similar to standard FLP are named as "hidden" or "masked" FLPs (mFLP). [24][25][26][27][28][29] In general, mFLP show weak LA/LB interactions that allow them to dissociate and react with other molecules. (Pyridin-2-ylmethyl)aluminium and gallium derivatives have been synthesized and their structure has been characterized by X-ray crystallography (Figure 1).…”

“…Among the different types of FLP systems, those that show a classical LA/LB pair adduct but present a reactivity similar to standard FLP are named as “hidden” or “masked” FLPs (mFLP) [24–29] . In general, mFLP show weak LA/LB interactions that allow them to dissociate and react with other molecules.…”