Preparation via Sterically Promoted S_N2′ Substitution and Structural Characteristics of a Mes*‐Substituted Tertiary Ethynylphosphine

Abstract

The reaction of a sterically encumbered 2‐bromo‐3‐silyloxyphosphapropene [(Z)‐Mes*‐P = C(Br)CH(OSiMe3)Mes; Mes* = 2,4,6‐tBu3C6H2, Mes = 2,4,6‐Me3C6H2] and butyllithium afforded a bulky ethynylphosphine [Mes*P(nBu)C≡CMes] via SN2′ reaction of the alkyllithium and subsequent beta‐elimination of HBr. The orbital‐controlled reaction and prohibition of the halogen–metal exchange would be induced by the steric encumbrance of the mesityl group. Structural characteristics of the novel ethynylphosphine were also discussed in views of steric encumbrance as well as stereochemistry. The remarkable distortion of Mes* aromatic ring was further discussed according to DFT calculations.