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Reactions of Thioketones Possessing a Conjugated CC Bond with Diazo Compounds
Author(s) -
Egli Daniel H.,
Linden Anthony,
Heimgartner Heinz
Publication year - 2006
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.200690274
Subject(s) - chemistry , diazo , thiirane , conjugated system , zwitterion , cycloaddition , yield (engineering) , medicinal chemistry , ring (chemistry) , ylide , stereochemistry , organic chemistry , molecule , catalysis , polymer , materials science , metallurgy
The reactions of several thioketones containing a conjugated CC bond with diazo compounds were investigated. All of the selected compounds reacted via a 1,3‐dipolar cycloaddition with the CS 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.