Metal-Carbenoid-Mediated Selective Transformation: Experimental and DFT Studies of Ag, Pd, and Rh with Enaminones and Diazoesters

Transition-metal-catalyzed transfer of a carbene group
via in situ
generated carbenoid intermediates from α-diazocarbonyls is a
powerful method for initiating diverse cascade sequences that rapidly
lead to the generation of structural complexity. Despite significant
advancements in carbenoid-enabled catalytic pathways, such as insertions
and cyclopropane formation, there has been limited exploration of
the selective control of catalytic processes involving carbenoid chemistry.
In this study, we reported a metal-carbenoid-mediated cascade transformation
approach that allows for selective control by employing different
transition metals, including silver, palladium, and rhodium, assisted
by a comprehensive density functional theory (DFT) mechanism investigation.
Through detailed mechanistic studies, we demonstrate that silver-carbenoids
and rhodium-carbenoids yield distinct tandem cyclization products,
while palladium-carbenoids afford quaternary α-imine compounds
as the final product through direct proton transfer from the same
intermediate. Furthermore, the origin of the catalyst-dependent selectivity
is elucidated through DFT calculations.

过渡金属催化的卡宾（carbene）基团转移反应——以α-重氮羰基化合物（α-diazocarbonyls）原位生成的类卡宾（carbenoid）中间体为底物——是一种可引发多样级联反应、快速构建复杂分子结构的有力手段。尽管基于类卡宾的催化路径（如插入反应与环丙烷化反应）已取得显著进展，但针对类卡宾化学相关催化过程的选择性调控研究仍较为匮乏。本研究报道了一种由金属-类卡宾介导的级联转化策略，通过选用银、钯、铑等不同过渡金属即可实现选择性调控，并结合全面的密度泛函理论（DFT）机理研究对该过程进行系统阐释。通过细致的机理研究，我们发现银-类卡宾与铑-类卡宾可生成不同的串联环化产物，而钯-类卡宾则通过同一中间体的直接质子转移，生成季碳α-亚胺类化合物作为最终产物。此外，本研究通过DFT计算阐明了催化剂依赖型选择性的起源机制。