3-(tert-Butyldimethylsilyloxy)propyllithium is an organolithium reagent used in organic synthesis to introduce a protected 3-hydroxypropyl group. It functions as a strong nucleophile, reacting with electrophiles such as alkyl halides, carbonyl compounds, or epoxides to form new carbon-carbon bonds. The tert-butyldimethylsilyl (TBS) group protects the alcohol moiety, allowing selective functionalization that can be deprotected under mild conditions to reveal the hydroxyl group. This reagent is particularly valuable in the synthesis of pharmaceuticals, natural products, and advanced materials requiring precise control over chain length and functionality.