Catalytic semi-hydrogenation of alkynes using dihydrogen is an atom economical route for synthesizing alkenes. While almost all transition metals produce Z alkenes with variable efficiencies, heterogeneous catalysts that yield E alkenes are conspicuously uncommon. This is understandable as syn addition of H2 to the alkyne π system is a well-established stereochemical course. Recently, multicomponent systems consisting of noble metals and promoters have emerged as promising catalysts for this transformation by providing a reasonable balance between activity and selectivity. However, the interplay between the various components remains poorly understood. The inhomogeneity of the active sites coupled with the dynamic changes occurring during catalytic conditions makes it challenging to study these fundamental interactions. Our current work aims to develop such understanding through systematic study of functional mimics of such catalysts that are structurally well defined. More importantly, we demonstrate the utility of standard organometallic techniques in understanding E-selective semi-hydrogenation of alkynes catalyzed by bimetallic Rh-M (where M = Al or Ga) catalysts.

Probing promoter effects in E selective alkyne semi-hydrogenation

2019 Fall National Meeting

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