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Beckmann Fragmentation and Rearrangement. Part VI thian-3-one oximes. Fragmentation reactions no. 26

✍ Scribed by Cyril A. Grob; Junya Ide

Publisher
John Wiley and Sons
Year
1974
Tongue
German
Weight
652 KB
Volume
57
Category
Article
ISSN
0018-019X

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✦ Synopsis

Abstract

In 70% aqueous dioxane thian‐3‐one anti‐oxime p‐toluenesulfonate (tosylate) (8b) undergoes concerted fragmentation to the methylidenesulfonium ion 14, part of which recyclizes to 1,3‐thiazepin‐4‐one (11). With the syn‐isomer 8b rearrangement to 1,4‐thiazepin‐3‐one (10) and fragmentation to 14 occur in the ratio 4:1. Analysis of the rate data in 80% ethanol shows that anti fragmentation is 142 times as fast as syn fragmentation, but only 26 times as fast as rearrangement of the ‘homomorphous’ thian‐4‐one oxime tosylate (18b). A comparison of the rates of cyclohexanone oxime tosylate 20, thian‐3‐ and ‐4‐one oxime tosylates reveals the rate retarding influence of sulfur. – The configurations assigned to the stereoisomeric thian‐3‐one oximes (8a) in the literature have to be reversed in the light of present results.

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Beckmann Fragmentation and Rearrangement
Beckmann Fragmentation and Rearrangement. Part VII. Fragmentation and cyclization of α-methylthio-ketoximes. Fragmentation reactions no. 27
✍ Cyril A. Grob; Junya Ide 📂 Article 📅 1974 🏛 John Wiley and Sons 🌐 German ⚖ 813 KB

## Abstract α‐Methylthio‐propiophenone __anti__‐oxime __p__‐toluenesulfonate (tosylate) (**12b**) fragments quantitatively in 80% ethanol yielding benzonitrile and a methylidenesulfonium ion **15**. The __syn__‐isomer, however, undergoes a __Beckmann__ rearrangement. The fragmentation of α‐methylth