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Phosphine-Mediated Iterative Arene Homologation Using Allenes.
Kui Zhang1, Lingchao Cai1, Xing Jiang1
1Department of Chemistry and Biochemistry, University of California , Los Angeles, California 90095-1569, United States.
Journal of the American Chemical Society
|August 22, 2015
Summary
Researchers developed a new multicomponent reaction using triphenylphosphine (PPh3) to synthesize functionalized naphthalenes from o-phthalaldehydes and allenes. This method offers a versatile route to complex polycyclic aromatic hydrocarbons.
Area of Science:
- Organic Chemistry
- Synthetic Chemistry
- Catalysis
Background:
- Multicomponent reactions offer efficient pathways for complex molecule synthesis.
- O-phthalaldehydes and allenes are versatile building blocks in organic synthesis.
- Developing novel synthetic methodologies for polycyclic aromatic hydrocarbons is crucial.
Purpose of the Study:
- To develop a novel multicomponent reaction for synthesizing functionalized naphthalenes.
- To explore the reaction mechanisms and scope using different allenes and nucleophiles.
- To extend the methodology for the synthesis of larger polycyclic aromatic hydrocarbons like anthracenes and tetracenes.
Main Methods:
- Triphenylphosphine (PPh3)-mediated reaction of o-phthalaldehydes, nucleophiles, and monosubstituted allenes.
- Reaction of o-phthalaldehydes with 1,3-disubstituted allenes in the presence of PPh2Et.
- Mechanistic studies involving intermediate preparation and mass spectrometry.
- Iterative application of the reaction using carboxylic acids as pronucleophiles.
Main Results:
- Synthesis of functionalized non-C2-symmetric naphthalenes in synthetically useful yields.
- Obtention of naphthalene derivatives in up to quantitative yields using 1,3-disubstituted allenes and PPh2Et.
- Elucidation of a tandem γ-umpolung/aldol/Wittig/dehydration mechanism for the PPh3-mediated reaction.
- Successful iterative synthesis of anthracenes and tetracenes.
Conclusions:
- The developed multicomponent reaction provides an efficient and versatile route to substituted naphthalenes.
- The reaction mechanism involves a complex tandem process, elucidated through detailed studies.
- The methodology is extendable for the synthesis of larger polycyclic aromatic systems, highlighting its broad applicability.
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