One-Step Synthesis of Aryl Monomers for Silicones Enabled by Mechanistic Study of Intermolecular Dehydrogenative C–H Silylations

Various aryl and heteroaryl monomers for polysiloxane materials are finally accessible by intermolecular dehydrogenative C–H silylation between commercial (hetero)arenes and the industry-relevant triethoxysilane. The development of well-defined rhodium catalysts enables the silylation of triethoxysilane, which is known for poor reactivity in this silylation and prone to undergo the redistribution side reaction. For the silylation of electronically unactivated arenes, portionwise addition of the silane is necessary to ensure a high efficiency. Mechanistic investigation including computational study led to the isolation of two important catalytic intermediates and their dynamic interconversion, which provide mechanistic insight into the importance of portionwise addition and the intrinsic difference between arenes and heteroarenes in the silylation. In addition to their monomer roles, (hetero)aryl triethoxysilanes can be broadly utilized as versatile intermediates or coupling agents in chemical synthesis.