Photochemical Synthesis of 3, 4-Annulated Tetrahydrothiophenes

Kiesewetter, R; Margaretha, P.

doi:10.1080/03086648808072884

Cited by 2 publications

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“…Again in agreement with [ 191, radicals 4 bearing a substituent on C( 1) (originally on the alkene) undergo stereoselective ring closure to 3,4-cis-disubstituted thiolanes. As already reported [7], irradiation of l a in MeOH containing penta-1 ,4-diene affords a 6 : 1 mixture of 22/23 via intermediates 24 and 25 (Scheme 10).…”

Section: (100)mentioning

confidence: 63%

Photochemistry of Thiophen‐2(5H)‐ones

Kiesewetter

Margaretha

1989

Helvetica Chimica Acta

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Dedicated to Prof. Dr. 0. E. Polunsky on the occasion of his 70th birthday (4.XI. 88)Mechanistic evidence for the light-induced ring opening of thiophen-2(5H)-ones 1 in alcohols affording c@-unsaturated mercapto esters 2 is presented. Regio-and stereochemical aspects of the ring closure of alkenylthio (type 3) radicals 15 and 17 to S-heterocycles 16 and 18, of 3-thiahex-5-enyl radicals 4 to (tetrahydrothien-3-yl)methyl radicals 6 and of (2,3-dihydrothien-3-yl)methyl radicals 30 (type 7, but-3-enyl radicals) to cyclopropanemethyl radicals 29 are discussed. Irradiation (A. 350 nm) of 1 in cyclohexane in the presence of 2,3-dimethylbut-2-ene affords [2 + 21 cycloadducts 14 albeit in very low yields.We have recently reported [ 1-71 that on irradiation thiophen-2(5H)-ones 1 behave different from the corresponding 0-heterocycles. While furan-2(5H)-ones exhibit a typical enone-like behaviour yielding cyclodimers, [2 + 21 cycloadducts with alkenes or photoreduction products in alcohols from their triplet state [S] [9], the unsaturated thiolactones 1 undergo ring opening in alcohols to give a$-unsaturated mercapto esters 2 from the excited singlet state. Mercapto esters 2 undergo consecutive light-induced S-H homolysis to afford alkenylthio radicals 3 which in reacting with alkenes or alkynes proved to be useful synthetic intermediates for one-pot syntheses of thiolanes, 2,3-dihydrothiophenes as well as bi-and tricyclic thiolane derivatives via intermediates 4-7 (Scheme 1). Such -Scheme 1

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Section: (100)mentioning
confidence: 63%

Photochemistry of Thiophen‐2(5H)‐ones
Kiesewetter
¹
,
Margaretha
²

1989
Helvetica Chimica Acta
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ChemInform Abstract: Photochemical Synthesis of 3,4‐Annulated Tetrahydrothiophenes.
Kiesewetter
¹
,
Margaretha
²

1989
ChemInform
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0
0
0
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~~show abstract~~

Photochemical Synthesis of 3, 4-Annulated Tetrahydrothiophenes

Cited by 2 publications

References 10 publications

Photochemistry of Thiophen‐2(5H)‐ones

Photochemistry of Thiophen‐2(5H)‐ones

ChemInform Abstract: Photochemical Synthesis of 3,4‐Annulated Tetrahydrothiophenes.

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