Cyclisation versus 1, 1‐Carboboration: Reactions of B(C6F5)3 with Propargyl Amides. Issue 36 (6th August 2013)

• Record Type: Journal Article
• Authors: Melen, Rebecca L.; Hansmann, Max M.; Lough, Alan J.; Hashmi, A. Stephen K.; Stephan, Douglas W.
• Is Part Of: Chemistry. Volume 19:Issue 36(2013)
• Page Start: 11928
• Page End: 11938
• Publication Date: 2013-08-06
• Subjects: Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.201301899
• Languages: English
• ISSNs: 0947-6539

Abstract

<abstract abstract-type="main" xml:lang="en"> <title>Abstract</title> <p>A series of propargyl amides were prepared and their reactions with the Lewis acidic compound B(C₆F₅)₃ were investigated. These reactions were shown to afford novel heterocycles under mild conditions. The reaction of a variety of <italic>N</italic>‐substituted propargyl amides with B(C₆F₅)₃ led to an intramolecular oxo‐boration cyclisation reaction, which afforded the 5‐alkylidene‐4, 5‐dihydrooxazolium borate species. Secondary propargyl amides gave oxazoles in B(C₆F₅)₃ mediated (catalytic) cyclisation reactions. In the special case of disubstitution adjacent to the nitrogen atom, 1, 1‐carboboration is favoured as a result of the increased steric hindrance (1, 3‐allylic strain) in the 5‐alkylidene‐4, 5‐dihydrooxazolium borate species.</p> </abstract>