Use of Reagent in Default

Cyclodextrins monoazide 14a-b can also be synthesized by direct substitution reaction, using triphenylphosphine, carbon tetrabromide, and Hthium azide in DMF, but the yields are modest [24]. 

Sterically hindered silyl chlorides, such as tert-butyldimethylsilyl chloride, can also be used to protect a single hydroxyl on the primary rim, giving cyclodextrins 16a-b in about 40% yield. After alkylation of all the other positions and deprotection of the silyl ether, cyclodextrins with a unique primary hydroxyl can be obtained [25]. 

Direct monofunctionalization of cyclodextrins is possible using a reagent in default, but has its limitations yields are usually modest, and the products are obtained after careful and sometimes difficult purification. 

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