TiO2 (P25) nanoparticle catalyzed C-alkylation and quinoline synthesis via the borrowing hydrogen method

Abstract

Creating new, environmentally friendly catalytic systems for producing C–C bonds from renewable feedstock is a challenging objective in synthetic chemistry. Traditional methods often use expensive noble metals, organic or organometallic reagents, or toxic halides with co-catalysts or additives. However, borrowing hydrogen (BH) or hydrogen auto-transfer (HAT) technology offers a simple and cost-effective alternative for creating C–C bonds using readily available alcohols as alkylating agents. This study shows that commercial TiO₂ nanoparticles can act as a heterogeneous catalyst for C-alkylation reactions via a hydrogen-borrowing mechanism. The TiO₂ catalyst was effective in producing high yields of C-alkylated products from acetophenones and primary alcohols, and reusability tests showed that the catalyst was robust and stable. The TiO₂ catalyst was also capable of catalyzing multistep reactions to produce quinolines from 2-aminobenzyl alcohol and ketones with yields of up to 96.0%. Control experiments showed that the reaction pathway involved borrowing hydrogen. The use of this heterogeneous catalyst offers several advantages over traditional homogeneous catalysts, including lower cost, greater functional group tolerance, etc.