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1,5-Dipolar electrocyclizations in reactions of alpha-Thioxo Ketones and alpha-Thioxo Thioamides with Diazo compounds


Egli, D H; Linden, A; Heimgartner, H (2006). 1,5-Dipolar electrocyclizations in reactions of alpha-Thioxo Ketones and alpha-Thioxo Thioamides with Diazo compounds. Helvetica Chimica Acta, 89(9):1910-1926.

Abstract

Several reactions of a-thioxo ketones and a-thioxo thioamides with diazo compounds were investigated. Most of them proceeded via a reactive thiocarbonyl ylide, which underwent a [2+3] cycloaddition with the a-thioxo ketone to give the 'Schönberg products' 17–19 or a 1,5-dipolar electrocyclization to give the corresponding five membered 1,3-oxathioles (i.e., 13, 20a, 20b, 21, and 25) and 1,3-dithioles (i.e., 33, 34, and 35), respectively. In the case of thioamide 32, the thiocarbonyl ylides underwent a competitive 1,3-dipolar electrocyclization to yield the corresponding thiiranes. In these cases, spontaneous desulfurization led to the corresponding alkenes 36 and 37. The nature of the employed thiocarbonyl
or diazo compounds seem to be decisive for the reaction pathway. When the diazo compound bears at least one H-atom in the b-position to the diazo group (i.e., diazocyclohexane 15f), no products of an electrocyclization
could be isolated in the reactions with a-thioxo ketones or a-thioxo thioamides. The only products which were isolated in these cases were 2-[(cyclohex-1-enyl)sulfanyl]-1,2-diphenylethanone (22) and 2-[(cyclohex-1-enyl)sulfanyl]-N,N-dimethyl-2-phenylthioacetamide (38), which were formed
by a [1,4]-H shift of the corresponding thiocarbonyl ylides.

Abstract

Several reactions of a-thioxo ketones and a-thioxo thioamides with diazo compounds were investigated. Most of them proceeded via a reactive thiocarbonyl ylide, which underwent a [2+3] cycloaddition with the a-thioxo ketone to give the 'Schönberg products' 17–19 or a 1,5-dipolar electrocyclization to give the corresponding five membered 1,3-oxathioles (i.e., 13, 20a, 20b, 21, and 25) and 1,3-dithioles (i.e., 33, 34, and 35), respectively. In the case of thioamide 32, the thiocarbonyl ylides underwent a competitive 1,3-dipolar electrocyclization to yield the corresponding thiiranes. In these cases, spontaneous desulfurization led to the corresponding alkenes 36 and 37. The nature of the employed thiocarbonyl
or diazo compounds seem to be decisive for the reaction pathway. When the diazo compound bears at least one H-atom in the b-position to the diazo group (i.e., diazocyclohexane 15f), no products of an electrocyclization
could be isolated in the reactions with a-thioxo ketones or a-thioxo thioamides. The only products which were isolated in these cases were 2-[(cyclohex-1-enyl)sulfanyl]-1,2-diphenylethanone (22) and 2-[(cyclohex-1-enyl)sulfanyl]-N,N-dimethyl-2-phenylthioacetamide (38), which were formed
by a [1,4]-H shift of the corresponding thiocarbonyl ylides.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Department of Chemistry
Dewey Decimal Classification:540 Chemistry
Language:English
Date:2006
Deposited On:06 Dec 2011 07:41
Last Modified:18 Apr 2018 11:41
Publisher:Verlag Helvetica Chimica Acta
ISSN:0018-019X
Funders:Swiss National Science Foundation, F. Hoffmann-La Roche AG, Basel
OA Status:Green
Publisher DOI:https://doi.org/10.1002/hlca.200690182
Project Information:
  • : FunderSNSF
  • : Grant ID
  • : Project TitleSwiss National Science Foundation
  • : Funder
  • : Grant ID
  • : Project TitleF. Hoffmann-La Roche AG, Basel

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