2-Vinylcyclobutanones by Cycloaddition of Vinylketenes to Simple Olefins

✍ Scribed by David A. Jackson; Max Rey; André S. Dreiding

• Publisher: John Wiley and Sons
• Year: 1983
• Tongue: German
• Weight: 719 KB
• Volume: 66
• Category: Article
• ISSN: 0018-019X
• DOI: 10.1002/hlca.19830660744

✦ Synopsis

Abstract

Selected [2+2]‐cycloadditions of three alkylvinylketenes 2 to one mono‐ and seven dialkyl‐olefins 3 yielded eleven 2‐alkyl‐2‐vinylcyclobutanones 4 (Tables 1 and 2). Three methods were compared, all involving in situ generation of the ketenes 2 by HCl‐elimination from α,β‐unsaturated acid chlorides 1; the most effective employed a large excess of olefin 3 and a high reaction temperature. The [2+2]‐cycloadditions were fully regio‐ and stereoselective with respect to the olefin 3, but less so with respect to the ketene 2, so that ‐ where possible ‐ two stereoisomers of 4 resulted, namely A and B, whose configurations were determined from their ^1^H‐NMR, spectra, mechanistic considerations and, in one case, 4f, by chemical correlation with a previously known cycloadduct 8.