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Beckmann Fragmentation and Rearrangement. Part VI thian‐3‐one oximes. Fragmentation reactions no. 26
Author(s) -
Grob Cyril A.,
Ide Junya
Publication year - 1974
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.19740570832
Subject(s) - chemistry , beckmann rearrangement , fragmentation (computing) , cyclohexanone oxime , oxime , rearrangement reaction , medicinal chemistry , ion , stereochemistry , organic chemistry , cyclohexanone , catalysis , computer science , operating system
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.