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Valenzisomerisierung von cis-Dienonen, III Lichtinduzierte Umlagerung von 5-Phenyl-penta-2,4-dienaldehyden [1]

✍ Scribed by P. Schiess; ChR. Suter

Publisher
John Wiley and Sons
Year
1971
Tongue
German
Weight
698 KB
Volume
54
Category
Article
ISSN
0018-019X

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✦ Synopsis

Abstract

Irradiation of 5‐phenyl‐2,4‐pentadienaldehydes 1 and 2 leads to a rapid cis, trans‐isomerization of the 4,5‐double bond followed by formation of unsaturated ketenes 7 and 12, respectively, through a [1.5]‐hydrogen shift. In the dark, ketenes 7 and 12 revert at room temperature to the 5‐phenyl‐2,4‐pentadienaldehydes 1 und 2. Activation parameters and solvent dependence have been determined for this remarkably facile [1.5]‐sigmatropic rearrangement. The ketenes 7 and 12 are stable below − 20° in inert solvents. With alcohols and amines mixtures of α,β‐ and β,γ‐unsaturated acid derivatives are formed. Upon extended irradiation of 7 and 12 in aprotic solvents olefins 9 and 13 are formed through decarbonylation.

📜 SIMILAR VOLUMES

Valenzisomerisierung von cis-Dienonen, I
Valenzisomerisierung von cis-Dienonen, II. 5-Phenylpenta-2, 4-dienaldehyde [1]
✍ P. Schiess; R. Seeger; Chr. Suter 📂 Article 📅 1970 🏛 John Wiley and Sons 🌐 German ⚖ 726 KB

Phenylpenta-2,4-dienaldehydes 4 and 7 show an uncatalized cis-trans-isomerization of the 4,5-d0uble bond above 70 "C. The negative value of the activation entropy for these reactions points to the formation of the bicyclic valence isomeric 2H-Pyrans 5 and 8 respectively in the rate determining step.

Valenzisomerisierung von cis-dienonen IV
Valenzisomerisierung von cis-dienonen IV. Die vier stereoisomeren Formen von 4-Methyl-6-phenyl-3, 5-hexadien-2-on
✍ P. Schiess 📂 Article 📅 1972 🏛 John Wiley and Sons 🌐 German ⚖ 419 KB

## Abstract (__Z,Z__)‐4‐Methyl‐6‐phenyl‐3,5‐hexadien‐2‐one (**5**) is converted to its (__Z,E__)‐isomer **6** at 35° in the dark. This ready, uncatalysed __cis,trans__‐isomerization is shown to proceed through 2__H__‐pyran **9**. Irradiation of either stereoisomeric dienone **6, 7** or **8** at 0°