Addition Reactions: Polar Addition

Regioselective Electrophilic Addition to Propargylic B(MIDA)s Enabled by β‐Boron Effect

“…Electrophilic addition reaction to alkynes is of fundamental importance in organic chemistry. [ 1 ] Alkynes are readily available and their triple bond allows for easy modifications, enabling the facile creation of diverse compounds from simple feedstocks. [ 2 ] However, unsymmetrical alkynes pose a challenge in electrophilic addition reactions, as the addition may occur in two different directions, reducing the usefulness of the reaction ( Scheme 1 A ).…”

“…[ 2 ] However, unsymmetrical alkynes pose a challenge in electrophilic addition reactions, as the addition may occur in two different directions, reducing the usefulness of the reaction ( Scheme 1 A ). [ 1 , 2 , 3 ] To overcome this issue, a common strategy is to use terminal alkynes as substrates, following Markovnikov's rule. [ 4 ] The underlying reason for this selectivity is the preferential formation of more stable carbocation intermediates that are involved in the mechanism, given that this step is often rate‐determining.…”

“…[ 13 ] We thus hypothesized that the same effect might also be applicable to the electrophilic addition reaction of alkynes. However, due to the sluggish nature of the reactions of alkynes with electrophilic reagents compared to the corresponding reactions of alkenes, more severe conditions are often required [ 1 , 2 , 3 ] These harsher conditions may lead to the decomposition of the boryl moiety and compromise the regioselectivity. In this paper, we present how the β ‐boron effect can significantly enhance the reactivity of internal alkynes toward various types of electrophilic addition reactions.…”