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Published on: May 26, 2019
Functionalized Chromans from ortho-Quinone Methides and Arylallenes
Kornkamon Akkarasereenon1, Paratchata Batsomboon2, Somsak Ruchirawat1,2,3
1Program in Chemical Sciences, Chulabhorn Graduate Institute, Chulabhorn Royal Academy, 906 Kamphaeng Phet 6 Road, Laksi, Bangkok 10210, Thailand.
ortho-Quinone methides reacted with arylallenes via cycloaddition, forming 3-methylene-2-arylchromans. These intermediates allow diverse functionalization for creating complex organic molecules.
Area of Science:
- Organic Chemistry
- Synthetic Methodology
- Heterocyclic Chemistry
Background:
- ortho-Quinone methides (o-QMs) are reactive intermediates.
- Arylallenes are versatile building blocks in organic synthesis.
- Cycloaddition reactions are powerful tools for constructing cyclic systems.
Purpose of the Study:
- To explore the [4+2]-cycloaddition reaction between o-QMs and arylallenes.
- To synthesize 3-methylene-2-arylchromans.
- To investigate the functionalization of these chroman derivatives.
Main Methods:
- Formal [4+2]-cycloaddition reaction between o-QMs and arylallenes.
- Regioselective addition at the styrenyl olefin.
- Stereoselective synthesis when R is not H.
- Subsequent functionalization reactions including epoxidation, oxidation, rearrangement, and cross-coupling.
Main Results:
- Synthesis of 3-methylene-2-arylchromans in moderate to good yields (up to 88%).
- Moderate stereoselectivity (up to 5:1) observed, influenced by the R group.
- Demonstrated utility of the chroman intermediates for diverse downstream transformations.
- Successful synthesis of various derivatives through epoxidation, oxidation, rearrangement, and Pd-catalyzed cross-coupling.
Conclusions:
- The [4+2]-cycloaddition of o-QMs with arylallenes is an efficient route to 3-methylene-2-arylchromans.
- The synthesized chromans serve as valuable platforms for further synthetic elaborations.
- This methodology provides access to a range of functionalized heterocyclic compounds.
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