Abstract
The activation of π‐bonds in diynyl esters has been investigated by using soft and hard Lewis acids. In the case of the soft selenium Lewis acid PhSeCl, sequential activation of the alkyne bonds leads initially to an isocoumarin (1 equiv PhSeCl) and then to a tetracyclic conjugated structure with the isocoumarin subunit fused to a benzoselenopyran (3 equiv PhSeCl). Conversely, the reaction with the hard Lewis acidic borane B(C6F5)3 initiates a cascade reaction to yield a complex π‐conjugated system containing phthalide and indene subunits.
Highlights
The activation of p-bonds in diynyl esters has been investigated by using soft and hard Lewis acids
The advent of frustrated Lewis pairs (FLPs) a decade ago has been a major advance in main-group chemistry, in metal-free catalysis.[1]
A particular theme within this area is the cooperative addition of FLPs across CÀC p-bonds (Scheme 1, bottom), which can occur in an intra- or intermolecular fashion.[3]
Summary
The activation of p-bonds in diynyl esters has been investigated by using soft and hard Lewis acids. Frustrated Lewis pairs (top) and 1,2-addition of FLPs to alkynes (bottom).
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