Cascade Phosphorylation/Cyclization of Propargylic Alcohols with R₂P(O)-H: Access to Diverse 6-Phosphoryl-6-vinyl...

Area of Science:

• Organic Chemistry
• Synthetic Chemistry
• Phosphorus Chemistry

Background:

• Indole derivatives are crucial scaffolds in medicinal chemistry.
• Efficient synthesis of complex heterocyclic compounds remains a challenge.

Purpose of the Study:

• To develop a novel, mild, and efficient method for synthesizing indeno[2,1-b]indoles.
• To explore a new reaction pathway involving cascade phosphorylation and cyclization.

Main Methods:

• Reaction of indole-containing propargylic alcohols with P(O)-H species.
• Utilizing mild reaction conditions.
• Employing a cascade phosphorylation/cyclization strategy.

Main Results:

• Successful synthesis of various 6-phosphoryl-6-vinyl indeno[2,1-b]indoles.
• Formation of one C-P bond and one C-C bond in a single procedure.
• Identification of a phosphorylated allene intermediate initiating a regioselective 5-exo-trig cyclization.

Conclusions:

• The described cascade reaction is an efficient and practical approach to valuable indeno[2,1-b]indoles.
• The study demonstrates a novel cyclization reaction mode.
• This method offers a new synthetic strategy for complex phosphorus-containing heterocycles.