Direct Reaction of Silica Gel with Butyllithium

Abstract

Silica gel with a variety of surface areas is found to react directly (no SOCl2 treatment required) with butyllithium to give a product with butyl groups attached. The extent of butyl group incorporation depends on available silica surface. With dehydrated 230–400 mesh silica gel, 7.4 mmoles of BuLi per g in pentane added in hexane gave silica with 2.5 mmoles of butyl groups per g provided that the silica gel was washed three times with cold water. It was found that water washing removes some unbutylated silicate increasing the apparent butyl group incorporation. The butyl-modified silica gel showed no chromatographic retention of 3-aminoquinoline in 50:50 hexane: dichloromethane or of thymol in hexane in contrast to unmodified silica gel which is known to strongly retain polar compounds, particularly basic ones. This contrast is demonstrated.