Base-Promoted [4 + 1]/[3 + 1 + 1] Bicyclization for Accessing Functionalized Indeno[1,2-c]furans

Area of Science:

• Organic Chemistry
• Synthetic Chemistry
• Heterocyclic Chemistry

Background:

• Indeno[1,2-c]furans are important heterocyclic scaffolds.
• Efficient synthesis of functionalized indeno[1,2-c]furans remains a challenge.

Purpose of the Study:

• To develop a novel, metal-free three-component bicyclization strategy.
• To synthesize densely functionalized indeno[1,2-c]furans.

Main Methods:

• Utilized readily accessible o-phthalaldehydes (OPA), isocyanides, and α-diazoketones.
• Employed a reaction pathway involving aldol-type addition, 1,2-hydride shift, 5-exo-trig cyclization, 1,4-addition, and oxo-5-exo-dig cyclization.

Main Results:

• Successfully established a metal-free synthesis of indeno[1,2-c]furans.
• Achieved generally good yields of the target compounds.
• Demonstrated continuous multiple bond-forming events, including C-C and C-O bonds.

Conclusions:

• The developed strategy provides an efficient route to functionalized oxo-heterocycles.
• This method offers rapid construction of complex molecular architectures.
• The approach is valuable for accessing novel indeno[1,2-c]furan derivatives.