We report an artificial molecular machine that moves along a track, iteratively joining building blocks to form an oligomer of single sequence with a continuous backbone of carbon-carbon bonds. The rotaxane features a macrocycle bearing an aldehyde-terminated chain and an axle containing different phosphonium ylides separated by rigid spacers. Each ylide is large enough to block the passage of the macrocycle, trapping the ring between the stopper at the terminus of original threading and the next ylide along the track. Once a building block is reachable, it is removed from the track through a Wittig reaction that adds it to the terminus of the growing chain. Operation on a four-barrier tetra(phosphonium salt) track produces a tetra(diphenylpropane) of single sequence linked through alkene bonds. The prototype extends the principle for molecular machines that build polymers by moving along tracks to the synthesis of sequence-encoded chains with continuous carbon backbones.

我们报道了一种沿着轨道运动的人造分子机器，它反复地连接构件以形成具有碳-碳键连续骨架的单一序列的低聚物。轮烷具有一个大环，该大环带有醛封端的链，其轮轴包含由刚性间隔基分隔开的不同的磷化氢。每个ylide的大小足以阻止大循环的通过，将环圈圈在原始螺纹末端的塞子和沿轨道的下一个ylide之间。一旦可以到达一个构造块，就可以通过Wittig反应将其从轨道上移除，并将其添加到增长链的末端。在四壁垒四（phosph盐）轨道上操作可产生通过烯烃键连接的单个序列的四（二苯基丙烷）。