Hydrosilane-Dependent Regiodivergence for Rhodium-Catalyzed Dearomative Hydrosilylation of Quinolines
Year: 2026
Type: preprint
Abstract: Regiodivergent dearomative hydroelementation (E = Si, B) of quinolines represent a powerful, atomeconomic strategy for the synthesis of biologically valuable 1,2- and 1,4-dihydroquinolines (DHQ) scaffolds. However, achieving such regiodivergent H[E] additions at the C2 and C4 positions within a unified catalytic system remains highly challenging. Herein, we report a simple [Rh(cod)Cl]2/PPh3 catalytic system that enables regioselective hydride incorporation dictated solely by the choice of hydrosilane (Ph2SiH2 vs. Me2RSiH, R = Et or Ph). While the Ph2SiH2-mediated 1,2-hydrosilylation protocol proceeds efficiently at 23 oC, the 1,4-hydrosilylation with Me2EtSiH requires a prolonged reaction time or an elevated temperature (23 to 50 oC) to achieve high yields. Preliminary mechanistic studies under the Ph2SiH2 vs. Me2PhSiH systems indicate that (i) chloro-free, phosphine-ligated Rh hydride species in situ generated during the initiation stage serves as the key resting species; (ii) a classic Chalk–Harrod sequence operates to yield the 1,2-DHQ irrespective of the hydrosilane used; (iii) the Me2PhSiH system promotes a facile isomerization of the kinetic 1,2-DHQ product to the 1,4-DHQ via an exclusive 3,4-hydrorhodation process; and (iv) the dearomative 1,2-hydrorhodation is reversible under the Ph2SiH2 system and the liberated 1,2-DHQ is completely resistant to subsequent isomerization.
Source: ChemRxiv
Authors: Mei Shu, Sehoon Park
Language: English
Subfield: Organic Chemistry
Field: Chemistry
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7223337791