Acylthioketene−Thioacylketene−Thiet-2-one Rearrangements

Abstract

Flash vacuum thermolysis (FVT) of 6-aryl-1,3-dioxine-4-thiones 9 leads to the formation of acylthioketenes 10, which are characterized by Ar matrix IR spectroscopy as well as on-line tandem mass spectrometry. The thioketenes 10 undergo a 1,3-shift of the aryl group to generate thioacylketenes 11. Ketenes 11 cyclize to 3-aryl-thiet-2-ones 12, which are also characterized by matrix IR spectroscopy and tandem mass spectrometry. The thiet-2-ones 12 undergo two kinds of reaction under the FVT conditions: (i) cheletropic CO extrusion with formation of arylthioketenes 13, and (ii) cycloreversion to COS and arylacetylene.

Ketene–acetylene [2 + 2] cycloadditions: cyclobutenone and/or oxete formation?

“…8 We have shown that vinylketenes rearrange readily to acylallenes by means of a 1,3-shift of electron rich substituents X such as amino and alkoxy groups (Scheme 2). See http://www.rsc.org./suppdata/ ob/b3/b309549e/ a general reaction for acyl-and imidoylketenes, 12 thioacylketenes, 13 and thioacylisocyanates, 14 and the 1,3-shift of amino groups are particularly fast. † Electronic supplementary information (ESI) available: tables of absolute energies of all calculated species.…”

“…There have been previous theoretical treatments of the 1,3-shifts in the oxoketene-oxoketene, 12a,d,16b,20 imidoylketeneoxoketenimine, 21 vinylketene-acylallene, 11 acylisocyanate-acylisocyanate, 12a acylthioketene-thioacylketene, 13 and acylisothiocyanate-thioacylisocyanate 14 rearrangements.…”

Formation of Cumulenes, Triple-Bonded, and Related Compounds by Flash Vacuum Thermolysis of Five-Membered Heterocycles

“…[11] Scheme 1 An interesting property of the acylcumulenes 2 and 5 is their isomerization due to 1,3-shifts of the acyl substituents. [6] Thus, the acylketenes undergo degenerate rearrangements, [12] imidoylketenes interconvert with acylketenimines, [13] thioacylketenes with acylthioketenes, [14] and acylallenes with vinylketenes [15] (6 Ǟ 7). These rearrangements are facilitated by the interaction between a high-lying filled orbital (lone pair) on the migrating group R and a lowlying LUMO of the cumulene, which possesses a large inplane coefficient on the central carbon atom.…”

“…[20] Further FVT of thietones causes extrusion of CO and formation of thioketenes, such as the fulvene derivative 13. [14,21] FVT of indandione 16, phthalide 17, and benzocyclopropene 18 have been used in a similar manner in the preparation of vinylidenecyclopentadiene (''fulvenallene'' 19) (Scheme 2). [22] Another isomer of phthalide, 2-coumaranone 20, gives fulvene 22 instead, by double CO extrusion.…”

Photochemistry of Spiro[6H‐[1,3]Oxathiin‐2,2′‐tricyclo[3.3.1.13,7]decan]‐ 6‐one

“…Flash vacuum pyrolysis studies of either 1,3-dioxin-4-thiones [14] or of 1,6-dioxa-6a-l 4 -thiapentalenes [15] indicate these species to be slightly lower in energy than the isomeric acylthioketenes but nothing is known about their behavior in solution. The alcohol adducts of 10, i.e., 3-sulfanylacrylates 13, and the corresponding thiolate ions are known to be stable only at temperatures below 08 [16], as they undergo both rapid oligomerization as well as oxidation to disulfanes [7].…”