Hydroxyl groups stannylene derivatives

Bu2SnO, benzene BnBr, DMF, heat, 80% yield. This method has also been used to protect selectively the anomeric hydroxyl in a carbohydrate derivative. The replacement of Bu2SnO with Bu2Sn(OMe)2 improves the process procedurally. The use of stannylene acetals for the regioselective manipulation of hydroxyl groups has been reviewed. ... 

The stannylenes of sugar derivatives are prepared in the same way from derivatives in which two non-protected hydroxyl groups remain at appropriate sites. Acid chlorides react with stannylenes in less than 1 min at room temperature in a benzene or a DMF solution to give, regioselectively, the monoester. Benzyl and allyl halides lead to the corresponding ethers in warm DMF. Here again, the reaction is regioselective. 

The selective functionalization of the C-2 hydroxyl group of IV-carbobenzyloxy-4,6-0-benzylidine-l-deoxynojiTimycin by use of dibutyl stannylene derivatization of the C-2 and C-3 hydroxyl groups has been achieved. By this method the 2-O-benzoyl and 2-0-tosyl derivatives were made. 

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