Eine Synthese methylierter Epoxyhydroazulenone durch intramolekulare [4 + 3]-Cycloaddition einer aus 1,1-Dichloro-6-(3-methylfur-2-yl)hexan-2-on erzeugten Oxyallyl-Zwischenstufe
✍ Scribed by Roland Kaiser; Baldur Föhlisch
- Publisher
- John Wiley and Sons
- Year
- 1990
- Tongue
- German
- Weight
- 675 KB
- Volume
- 73
- Category
- Article
- ISSN
- 0018-019X
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✦ Synopsis
A synthesis of Methylated Epoxyhydroazulenones by Intramolecular [4 + 3] Cycloaddition of an Oxyallyl Intermediate, Generated from 1,1‐Dichloro‐6‐(3‐methyl‐2‐furyl)hexan‐2‐one
(Z)‐3‐Methylpent‐2‐en‐4‐yn‐1‐ol (7) was transformed to 2‐(4‐chlorobutyl)‐3‐methylfuran (4b) and 2‐(but‐3‐enyl)‐3‐methylfuran (10a) by C‐alkylation and 5‐exo‐dig cyclization. The Grignard derivative formed from 4b gave 1,1‐dichloro‐6‐(3‐methylfur‐2‐yl)hexan‐2‐onc (1b) on reaction with dichloroacetyl chloride. This dichloromethyl ketone undergoes a base‐induced cyclization to form diastereoisomeric 7‐chloro‐1,2,3,6,7,8a‐hexahydro‐4‐methyl‐8H‐3a,6‐epoxyazulen‐8‐ones (3bα and 3bβ) by way of an intramolecular [4+3] cycloaddition of an oxyallyl intermediate 2b. By dechlorination and hydrogenation of 3bβ, the tricyclic hydroepoxyazulenones 18 and 19 have been synthesized.