halodesilylation

Halodesilylation is a transformation in organosilicon chemistry in which a silicon substituent on a vinyl or alkynyl carbon is replaced by a halogen, yielding vinyl halides or alkynyl halides. The reaction typically proceeds via activation of the carbon–silicon bond by an electrophilic halogen source, followed by desilylation to form the C–X bond. In many protocols, N-halosuccinimides (NXS; X = Cl, Br, I) are used in combination with a fluoride source or silicate to promote silicon–carbon bond cleavage, often in polar aprotic solvents. The choice of halogen source and desilylation conditions can influence regio- and stereoselectivity, with vinylsilane substrates commonly furnishing vinyl halides.

Substrates commonly include vinylsilanes and alkynyl silanes bearing SiR3 groups such as TMS, TES, or TBDMS. Halodesilylation tolerates a range of substituents and can be performed with different halogens (chlorides, bromides, iodides) depending on the electrophilic halogen source.

Products are vinyl halides (R–CH=CH–X) or alkynyl halides (R–C≡C–X). The process provides a straightforward route to halogenated unsaturated systems that are useful intermediates for cross-coupling and other transformations.

Mechanistically, the reaction is thought to involve initial halogenation at the carbon adjacent to silicon to give a silicon-stabilized intermediate, followed by cleavage of the Si–C bond and capture of the halide to form the C–X bond. Desilylation by fluoride or related nucleophiles completes the transformation.

Applications include streamlined synthesis of vinyl and alkynyl halides for subsequent cross-coupling, polymerization, and natural product synthesis.