A Phosphine‐Catalyzed Regioselective [3+2] Cycloaddition of Ethyl 5, 5‐Diarylpenta‐2, 3, 4‐trienoate with Aromatic Aldehydes and α, β‐Unsaturated Carbonyl Compounds. Issue 16 (13th May 2014)

• Record Type: Journal Article
• Authors: Wang, Lu‐Feng; Cao, Xiao‐Ping; Shi, Zi‐Fa; An, Peng; Chow, Hak‐Fun
• Is Part Of: Advanced synthesis & catalysis. Volume 356:Issue 16(2014)
• Page Start: 3383
• Page End: 3390
• Publication Date: 2014-05-13
• Subjects: Catalysis -- Periodicals; Organic compounds -- Synthesis -- Periodicals; Chemistry -- Periodicals; Chemistry, Technical -- Periodicals; Chemistry -- Periodicals; Catalysis -- Periodicals; Technology, Pharmaceutical -- Periodicals; 547.2
• DOI: 10.1002/adsc.201301000
• Languages: English
• ISSNs: 1615-4150

Abstract

<abstract abstract-type="main" xml:lang="en"> <title>Abstract</title> <p>Tributylphosphine‐catalyzed regioselective [3+2] cycloadditions between ethyl 5, 5‐diarylpenta‐2, 3, 4‐trienoate <bold>1</bold> and various aromatic aldehydes <bold>2</bold> to produce a wide variety of polysubstituted 2, 5‐dihydrofurans <bold>3</bold>, and between <bold>1</bold> and β‐unsubstituted α, β‐unsaturated carbonyl compounds <bold>5</bold> to give polysubstituted cyclopentenes <bold>6</bold> with a quaternary carbon center, are reported. In both cases the reaction partners approach each other <italic>via</italic> the sterically less hindered orientation to afford the target products in excellent regioselectivity. The reaction mechanism involved first the generation of a zwitterionic intermediate between the butatriene <bold>1</bold> and PBu<sub>3</sub>. For the formation of 2, 5‐dihydrofurans <bold>3</bold>, the preferred cyclization mode encompassed the nucleophilic attack of the α‐position of butatriene to the aldehydic carbon of <bold>2</bold>, followed by the ring closure between the aldehydic oxygen of <bold>2</bold> and the γ‐position of butatriene, which is the first report of a normal [3+2] cycloaddition between cumulenes and aldehydes. For the formation of cyclopentenes <bold>6</bold>, the reaction involved attack of the γ‐position of the butatriene to the electron‐deficient β‐position of the α, β‐unsaturated carbonyl compounds <bold>5</bold>, followed by the ring closure between the α‐position of <bold>5</bold> and the α‐position of butatriene, which shows a different regioselectivity to the previously reported [3+2] cycloadditions between butatriene and olefins.</p> <p> <boxed-text content-type="graphic" position="anchor" orientation="portrait"> <graphic position="anchor" mimetype="image" xlink:href="ark:/27927/pgh2ch4713q" orientation="portrait" xlink:type="simple" xmlns:xlink="http://www.w3.org/1999/xlink" /> </boxed-text> </p> </abstract>