Dual Chalcogen–Chalcogen Bonding Catalysis

The noncovalent S···O
bonding interaction is an
evolutionary force that has been smartly exploited by nature to modulate
the conformational preferences of proteins. The employment of this
type of weak noncovalent force to drive chemical reactions is promising
yet remains largely elusive. Herein, we describe a dual chalcogen–chalcogen
bonding catalysis strategy that the distinct chalcogen atoms simultaneously
interact with two chalcogen-based electron donors to give rise to
the catalytic activity, thus facilitating chemical reactions. Conventional
approaches to the Rauhut–Currier-type reactions require the
use of strongly nucleophilic Lewis bases as essential promoters. The
implementation of this dual chalcogen–chalcogen bonding catalysis
strategy allows the simultaneous Se···O bonding interaction
between chalcogen-bonding donors and an enone and an alcohol, enabling
the realization of the Rauhut–Currier-type reactions in a distinct
way. The further implementation of a consecutive dual Se···O
bonding catalysis approach enables the achievement of an initial Rauhut–Currier-type
reaction to give an enone product which further undergoes an alcohol-addition
induced cyclization reaction. This work demonstrates that the nearly
linear chalcogen-bonding interaction can differentiate similar alkyl
groups to give rise to regioselectivity. Moreover, the new strategy
shows its advantage as it not only enables less reactive substrates
working efficiently but tolerates inaccessible substrates using conventional
methods.

非共价S···O键相互作用是一种演化动力，已被自然界巧妙利用以调控蛋白质的构象偏好。利用这类弱非共价作用力驱动化学反应极具应用前景，但目前在很大程度上仍未得到充分探索。在此，我们报道了一种双硫族-硫族键（dual chalcogen–chalcogen bonding）催化策略：不同的硫族（chalcogen）原子可同时与两类基于硫族的电子给体相互作用，从而产生催化活性，进而促进化学反应的进行。传统的劳胡特-库里尔（Rauhut–Currier）型反应合成方法，需使用强亲核性路易斯碱（Lewis base）作为核心促进剂。采用本双硫族-硫族键催化策略，可实现硫族键给体与烯酮、醇之间同时发生的Se···O键相互作用，从而以全新路径实现劳胡特-库里尔型反应。进一步采用连续双Se···O键催化策略，可先完成初始劳胡特-库里尔型反应得到烯酮产物，随后该产物可进一步发生醇加成诱导的环化反应。本研究表明，近乎线性的硫族键相互作用可区分相似烷基，从而实现区域选择性（regioselectivity）。此外，该新策略的优势显著：不仅可使低反应活性底物高效参与反应，还能适配传统方法难以实现的底物。