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1,3‐Dipolar Cycloadditions, 100. Nitrones and Electrophilic Acetylenes; a New Rearrangement of 2,3‐Dihydroisoxazoles
Author(s) -
Huisgen Rolf,
Giera Henry,
Polborn Kurt
Publication year - 1997
Publication title -
liebigs annalen
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 0947-3440
DOI - 10.1002/jlac.199719970810
Subject(s) - chemistry , electrophile , dimethyl acetylenedicarboxylate , ring (chemistry) , enamine , medicinal chemistry , stereochemistry , cycloaddition , organic chemistry , catalysis
The readiness of 4‐isoxazolines, the 1,3‐cycloadducts of nitrones to acetylenic compounds, to undergo rearrangement is notorious. The cycloadducts of the ketonitrones 5 and 6 to dimethyl acetylenedicarboxylate, dicyanoacetylene, and methyl propiolate were isolated and characterized. The 4‐isoxazolines 7 and 8 harbor the tetramethylcyclobutanone ring; they isomerize ( 7 at 45°C, 8 at −10°C) to enamine β‐carbonyl compounds 16 and 17 which are derived from the ring‐enlarged tetramethylpyrrolidin‐3‐one. The structure of 16 was elucidated by X‐ray analysis.