5-Azido-3-O-propargyl-1,2-O-isopropylidene-α-D-ribofuranose (1) showed the possibility of undergoing topochemical azide–alkyne cycloaddition (TAAC) reaction to form 1,5-triazolyl linked polymers in the crystal. Surprisingly, when thermally activated, the molecules reach a conformational equilibrium wherein the native conformer reacts intermolecularly to form a 1,5-triazolyl linkage but the other conformer reacts either intermolecularly to form a 1,4-triazolyl linkage or intramolecularly to form 2. Thus, the TAAC reaction adopts three competing pathways, of which two generate two different types of linkages for chain-growth and the third one generates a chain breaker. While the random occurrence of the chain-breaker reaction ensures the formation of oligomers of different sizes, the permutative occurrence of two types of linkages in any n-mer produces 2ⁿ different oligomers of the same size.

中文翻译：

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拓扑化学反应中的三向竞争：叠氮化物-炔烃环加成反应导致晶体中大量产物的形成†

5-叠氮基-3- O-炔丙基-1,2- O-异亚丙基-α- D-呋喃核糖（1）显示可能发生拓扑化学叠氮化物-炔烃环加成（TAAC）反应形成1,5-三唑基连接的聚合物水晶。令人惊讶地，当被热活化时，分子达到构象平衡，其中天然构象异构体在分子间反应形成1,5-三唑基键，而另一个构象异构体在分子间反应形成1,4-三唑基键或在分子内反应形成2。。因此，TAAC反应采用三个竞争途径，其中两个产生链增长的两种不同类型的连接，第三个产生链断裂剂。尽管随机发生的链断裂反应可确保形成不同大小的低聚物，但在任何n -mer中两种键的排列发生均会产生2 ^n个相同大小的不同低聚物。