Using blue-light driven iron-catalysis to afford molecular diversity in phosphindole oxide derivatives

Area of Science:

• Organic Chemistry
• Catalysis
• Photochemistry

Background:

• Phosphine oxides are versatile building blocks in organic synthesis.
• Developing efficient catalytic methods for their functionalization remains a key challenge.
• Iron catalysis offers a sustainable and cost-effective alternative to precious metal catalysts.

Purpose of the Study:

• To develop a novel blue-light promoted iron-catalyzed reaction for synthesizing phosphole oxides.
• To explore the use of activated alkynes and secondary phosphine oxides as substrates.
• To investigate the influence of different iron precursors on reaction outcomes.

Main Methods:

• Blue-light irradiation at room temperature.
• Iron-catalyzed coupling of activated alkynes with secondary phosphine oxides.
• Utilized tert-butylhydroperoxide as an oxidant under argon atmosphere.
• Employed different iron precursors (Fe(NO3)3 and Fe(OTf)2) in various solvents (methanol and acetic acid).

Main Results:

• Successfully synthesized benzo[b]phosphole oxides using Fe(NO3)3 in methanol.
• Obtained 9-phenyltribenzo[b,e,g]phosphindole 9-oxide derivatives using Fe(OTf)2 in acetic acid.
• Control experiments indicated the involvement of radical processes in the reaction mechanism.

Conclusions:

• Established a new synthetic route to phosphole oxides via blue-light promoted iron catalysis.
• Demonstrated the versatility of the method by producing different phosphole oxide structures based on the iron precursor.
• Proposed a radical-based mechanism, providing mechanistic insights into the transformation.