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4.4.7.2.3.4 Palladium-Catalyzed (4 + 1) Cycloaddition with Silylenes

DOI: 10.1055/sos-SD-104-00395

Delvos, L. B.; Oestreich, M.Science of Synthesis Knowledge Updates, (20171102.

Amino-functionalized silylboronic ester 47 serves as a silylene precursor in palladium-catalyzed (4 + 1)-cycloaddition reactions with 1,3-dienes 97, giving access to a variety of silacyclopentenes 98, which are difficult to obtain by other methods (Scheme 44).[‌75‌] A catalyst screening revealed that bis(dibenzylideneacetone)palladium(0) and methyldiphenylphosphine as ligand are an optimal combination for this transformation. Substitution is allowed on every carbon atom of the diene, and several mono-, di-, and trisubstituted substrates form the corresponding silacyclopentenes 98 in good yields. Among other functional groups, even an alkene is compatible with the reaction conditions. A bulkier silylboron reagent with two phenyl groups at the silicon atom was used successfully at slightly higher reaction temperatures (50 °C), expanding the scope to cyclohexa-1,3-diene and gaseous buta-1,3-diene (not shown).

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