A Highly Efficient Chirality Switchable Synthesis of Dihydropyran‐Fused Benzofurans by Fine‐Tuning the Phenolic Proton of β‐Isocupreidine (β‐ICD) Catalyst with Methyl. Issue 29 (8th June 2015)

• Record Type: Journal Article
• Authors: Wang, Feng; Yang, Chen; Xue, Xiao‐Song; Li, Xin; Cheng, Jin‐Pei
• Is Part Of: Chemistry. Volume 21:Issue 29(2015)
• Page Start: 10443
• Page End: 10449
• Publication Date: 2015-06-08
• Subjects: Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.201501145
• Languages: English
• ISSNs: 0947-6539

Abstract

<abstract abstract-type="main" xml:lang="en"> <title>Abstract</title> <p>A highly enantioselective β‐isocupreidine (β‐ICD) catalyzed synthesis of dihydropyran‐fused benzofurans through [4+2] cycloaddition of allenoates and benzofuranone alkenes was developed. Switchable chirality inversion of cycloaddition products was achieved by replacing the phenolic proton of the catalyst with a methyl, demonstrating an amazing effect of minimal structural variation on inverting enantioselectivity. DFT calculations were utilized to elucidate the origin of the observed phenomena. Computation also provided a clue for a rational design in which the multi‐hydrogen bond with the alcohol additive was found to improve the enantioselectivity of the cycloaddition. Finally, the substrate scope was examined, in which a number of functionalized dihydropyran‐fused benzofurans could be obtained in high yields (up to 97 %) with very good regio‐ (&gt;20:1) and enantioselectivities (up to 98:2 e.r.).</p> </abstract>