A new method employing
iron(III) acetylacetonate along with visible
light is described to effect oxidative ring opening of cyclic ethers
and acetals with unparalleled efficiency. The method allows for a
photocatalytic radical chemistry approach to functionalize relatively
inert cyclic ethers into useful synthetic intermediates. The methodology
sheds further light on the use of underexplored iron complexes in
visible-light photochemical contexts and illustrates that simple Fe(III)
complexes can initiate redox processes from
4
LMCT excited
states.
A heterogenized iridium catalyst was employed to perform
photoredox
catalysis for a collection of mechanistically orthogonal reactions
using very low quantities of iridium (0.01–0.1 mol %). The
heterogenized construct consists of an organometallic iridium coordination
complex bonded to an aluminum metal oxide solid-state support via
an anchoring group. The solid-state support allows for easy recovery
and reusability of the catalyst. Evaluation of the catalytic activity
was performed with five different reactions, showing broad applicability
and demonstrating the general potential for a heterogenized strategy.
Moreover, the heterogenized catalyst was shown to be reusable up to
five times and also mediated the reactions with much higher efficiency
than the original processes by employing the corresponding homogeneous
catalyst. As a result of the low catalyst loadings employed, the feasibility
of reusage, and faster reaction times, this catalyst offers a more
sustainable option when precious metal catalysts are used in organic
synthesis. Finally, the catalyst was successfully applied to a gram-scale
reaction, showing it is susceptible to scalability.
A visible-light mediated alkoxy radical generation is described, which allows for a structurally divergent oxidative C(sp3)-H bond functionalization. This protocol employs a photoredox/iron dual catalysis allowing for an unprecedented chemoselective...
A very efficient one-pot procedure for the direct oxidation of aldehydes to esters mediated by visible-light is presented. Utilizing a combination of indium triflate and N-bromosuccinimide, NBS, with either ortho-esters or alcohols provided rapid access to a variety of esters. Certain substrates convert fully within a few seconds, other more challenging tert-butyl esters were formed in good yield after no more than 4 h.
Graphical abstract
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