Temporal separation of catalytic activities allows anti-Markovnikov reductive functionalization of terminal alkynes
作者:Le Li、Seth B. Herzon
DOI:10.1038/nchem.1799
日期:2014.1
There is currently great interest in the development of multistep catalytic processes in which one or several catalysts act sequentially to rapidly build complex molecular structures. Many enzymesâoften the inspiration for new synthetic transformationsâare capable of processing a single substrate through a chain of discrete, mechanistically distinct catalytic steps. Here, we describe an approach to emulate the efficiency of these natural reaction cascades within a synthetic catalyst by the temporal separation of catalytic activities. In this approach, a single catalyst exhibits multiple catalytic activities sequentially, allowing for the efficient processing of a substrate through a cascade pathway. Application of this design strategy has led to the development of a method to effect the anti-Markovnikov (linear-selective) reductive functionalization of terminal alkynes. The strategy of temporal separation may facilitate the development of other efficient synthetic reaction cascades. Multifunctional catalysts typically process substrates and intermediates concurrently. Here, a strategy is described to separate catalytic activities in the time domain (temporal separation). Application of this strategy has led to the development of a method to effect the anti-Markovnikov reductive functionalization of terminal alkynes; such an approach may facilitate the development of other synthetic reaction cascades.
Regioselective Reductive Hydration of Alkynes To Form Branched or Linear Alcohols
作者:Le Li、Seth B. Herzon
DOI:10.1021/ja307145e
日期:2012.10.24
The regioselective reductive hydration of terminal alkynes using two complementary dual catalytic systems is described. Branched or linear alcohols are obtained in 75-96% yield with >= 25:1 regioselectivity from the same starting materials. The method is compatible with terminal, di-, and trisubstituted alkenes. This reductive hydration constitutes a strategic surrogate to alkene oxyfunctionalization and may be of utility in multistep settings.
A Highly Active and Air-Stable Ruthenium Complex for the Ambient Temperature Anti-Markovnikov Reductive Hydration of Terminal Alkynes
作者:Mingshuo Zeng、Le Li、Seth B. Herzon
DOI:10.1021/ja501738a
日期:2014.5.14
partially dissociated from the ruthenium center (by protonation) in the reaction media, thereby generating a vacant coordination site for catalysis. These studies also show that this substituent increases hydrogenation activity by promoting activation of the reductant. At least three catalytic cycles, involving the decarboxylation of formicacid, hydration of the alkyne, and hydrogenation of the intermediate