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Photoisomerization of 2H,6H-Thiin-3-ones to 2-(Alk-1-enyl)thietan-3-ones

✍ Scribed by Erhan Er; Paul Margaretha

Publisher
John Wiley and Sons
Year
1992
Tongue
German
Weight
298 KB
Volume
75
Category
Article
ISSN
0018-019X

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✦ Synopsis

Abstract

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 CC bond on sulfur is discussed as possible intermediate.

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Ring Opening of 2-(Benzylamino)-2H-1,4-b
Ring Opening of 2-(Benzylamino)-2H-1,4-benzoxazin-3(4H)-ones and 2-Bromo-2H-1,4-benzoxazin-3(4H)-ones
✍ Janez Ilaš; Danijel Kikelj 📂 Article 📅 2008 🏛 John Wiley and Sons 🌐 German ⚖ 223 KB 👁 1 views

## Abstract Substituted 2‐(benzylamino)‐2__H__‐1,4‐benzoxazin‐3(4__H__)‐ones are unstable under alkaline and acidic conditions, undergoing opening of the benzoxazinone ring. 2‐Bromo‐2__H__‐1,4‐benzoxazin‐3(4__H__)‐ones show similar degradation under alkaline conditions, while replacement of Br at C