Although azidation by nucleophilic substitution is widely used in organic chemistry, it has a limitation for partially protected carbohydrate derivatives under typical reaction conditions used for azidation (heating with NaN3, phase-transfer catalyst (optional), DMF or DMSO) as it can cause substantial migration (70%) of O-acyl protective groups. Several approaches, including the use of a temporary protective group for the unprotected hydroxyl group, to avoid acyl migration have been compared. Addition of excess of ethyl trifluroacetate effectively suppressed benzoyl migration but inhibited substitution of the chlorine atom with the azido group. The most robust procedure involved addition of excess n-butyl formate to the reaction mixture. When this protocol was followed, migration of benzoyl groups in lactose derivatives with free hydroxy group at C-3′ or C-4′ was reduced to 4%, with the yield of the target, partially protected derivatives with an azido group in the aglycone approaching 92%.

中文翻译：

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部分保护的碳水化合物衍生物的叠氮化：有效抑制酰基迁移

尽管亲核取代的叠氮化在有机化学中被广泛使用，但在用于叠氮化的典型反应条件下（用 NaN3、相转移催化剂（可选）、DMF 或 DMSO 加热），它对部分保护的碳水化合物衍生物有限制，因为它会导致大量O-酰基保护基团的迁移 (70%)。已经比较了几种方法，包括对未保护的羟基使用临时保护基团，以避免酰基迁移。添加过量的三氟乙酸乙酯有效地抑制了苯甲酰基迁移，但抑制了氯原子被叠氮基取代。最稳健的程序包括向反应混合物中加入过量的甲酸正丁酯。当遵循这个协议时，