(4 + 2) Annulation of Cl^–NH₃⁺CH₂SiMe₂CH₂Cl and Propynones for the Synthesis of 1,3-Azasilinones

Abstract

A useful 1,3-N,Si reagent (Cl–NH3 +CH2­SiMe2CH2­Cl) and its (4 + 2) annulation with propynones have been developed. The (4 + 2) annulation is promoted by NaHCO3 via an intermolecular N-1,4-addition/intramolecular alkylation process, leading to 1,3-azasilinones in good yields. Diverse functionalization of the alkene, carbonyl, and nitrogen moieties on the 1,3-azasilinone has been demonstrated, showcasing the potential of the approach in the synthesis of bioactive molecules containing silaazacycles.

Intramolecular Ring Expansion of 3-Silaazetidine with Alkynes Enabled by Pd-Catalyzed Si–C Bond Activation

“…The reaction generally proceeds via formation of one chemical bond such as the Si–C, C–N, or C–C bond . Increasing interest has recently focused on (m+n)-cyclization, which enables sequential formation of two chemical bonds, leading to silaazacycles in a convergent manner (Scheme a, left) . In contrast to cyclization and (m+n)-cyclization, ring expansion of small silacycle rings , such as silacyclopropane, silacyclopropene, and silaaziridine with unsaturated bonds also enables construction of silaazacycles, but only was investigated in a very limited scope.…”