Reactions of Thioketones Possessing a Conjugated CC Bond with Diazo Compounds

✍ Scribed by Daniel H. Egli; Anthony Linden; Heinz Heimgartner

• Book ID: 102253846
• Publisher: John Wiley and Sons
• Year: 2006
• Tongue: German
• Weight: 251 KB
• Volume: 89
• Category: Article
• ISSN: 0018-019X
• DOI: 10.1002/hlca.200690274

✦ Synopsis

Abstract

The reactions of several thioketones containing a conjugated CC bond with diazo compounds were investigated. All of the selected compounds reacted via a 1,3‐dipolar cycloaddition with the CS group and subsequent N~2~ elimination to yield thiocarbonyl ylides as intermediates, which underwent a 1,3‐dipolar electrocyclization to give the corresponding thiirane 25, or, by a subsequent desulfurization, to give the olefins 33a and 33b. None of the intermediate thiocarbonyl ylides reacted via 1,5‐dipolar electrocyclization. If the α,β‐unsaturated thiocarbonyl compound bears an amino group in the β‐position, the reactions with diazo compounds led to the 2,5‐dihydrothiophenes 40a–40d. In these cases, the proposed mechanism of the reactions led once more to the thiocarbonyl ylides 36 and thiiranes 38, respectively. The thiiranes reacted via an S~N~i′‐like mechanism to give the corresponding thiolate/ammonium zwitterion 39, which underwent a ring closure to yield the 2,5‐dihydrothiophenes 40. Also in these cases, no 1,5‐dipolar electrocyclization could be observed. The structures of several key products were established by X‐ray crystallography.