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Photoisomerization of 2 H ,6 H ‐Thiin‐3‐ones to 2‐(Alk‐1‐enyl)thietan‐3‐ones
Author(s) -
Er Erhan,
Margaretha Paul
Publication year - 1992
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.19920750712
Subject(s) - chemistry , photoisomerization , enol , naphthalene , alkene , benzene , singlet state , medicinal chemistry , enone , photochemistry , alkyl , excited state , organic chemistry , isomerization , catalysis , physics , nuclear physics
Reaction of 3‐bromo‐3‐methylbutan‐2‐one ( 1 ) with mercapto‐esters 2 affords 5‐oxo‐3‐thiahexanoates 3 which cyclize to thiane‐3,5‐diones 4 . Conversion of these dicarbonyl compounds to their ethyl enol ethers 5–7 followed by reduction with LiAlH 4 gives 2 H ,6 H ‐thiin‐3‐ones 8–10 . On irradiation (350 nm) in either MeCN, benzene, or i‐PrOH, these newly synthesized heterocycles isomerize efficiently to 2‐(alk‐l‐enyl)thietan‐3‐ones 11–13 . The rearrangement seems to proceed from an excited singlet state, as it is not quenched by naphthalene, and also occurs with the same efficiency in the presence of added alkene. A (9‐S‐3) sulfuranyl‐alkyl biradical formed by bonding of C(α) of the enone CC bond on sulfur is discussed as possible intermediate.