Abstract：
The synthesis of strained carbocyclic building blocks is relevant for Medicinal Chemistry, and methylenecyclobutanes are particularly challenging with current synthetic technology. Careful inspection of the reactivity of [1.1.1]propellane and diboron reagents has revealed that bis(catecholato)diboron (B2cat2) can produce a bis(borylated) methylenecyclobutane in a few minutes at room temperature. This reaction constitutes the first example of B-B bond activation by a special apolar hydrocarbon and also the first time that propellane is electrophilically activated by boron. Mechanistic studies including in situ NMR kinetics and DFT calculations demonstrate that the diboron moiety can be directly activated through coordination with the inverted sigma bond of propellane, and reveal that DMF is involved in the stabilization of diboronate ylide intermediates rather than the activation of the B-B bond. These results enable new possibilities for both diboron and propellane chemistry, and for further developments in the synthesis of methylenecyclobutanes based on propellane strain release.
摘要：
应变碳环结构单元的合成与药物化学有关，和亚甲基环丁烷在当前的合成技术中尤其具有挑战性。仔细检查[1.1.1]推进剂和二硼试剂的反应性，发现双（儿茶酚）二硼（B2cat2）可以在室温下在几分钟内产生双（硼化）亚甲基环丁烷。该反应构成了通过特殊的非极性烃活化B-B键的第一个例子，也是第一次用硼亲电活化推进剂。包括原位NMR动力学和DFT计算在内的机理研究表明，二硼部分可以通过与推进剂的倒σ键配位而直接活化。并揭示DMF参与二硼酸酯中间体的稳定而不是B-B键的活化。这些结果为二硼和推进剂化学提供了新的可能性，并进一步发展了基于推进剂菌株释放的亚甲基环丁烷的合成。
