Angeli rearrangement

The so-called isoxazoline transposition or Angelis rearrangement (Scheme 123) involves the conversion of methyl-furoxans by treatment with alkoxides or alcoholic alkali hydroxides into the oximes of isoxazolidin-4-ones 591. 

In general, furoxans are fairly stable compounds in acid solution but are sensitive to bases [6, 9]. This is true in particular for the parent ring and for the 4- and 3-monosubstituted compounds. The former undergoes extensive decomposition, while the latter two produce a-hydroxyimino substituted nitrile oxides 5 and a-nitro substituted nitriles 6, respectively. 4-Aryl-3-methylfuroxans 7, unlike their 4-methyl isomers, give Angeli s rearrangement, namely they are converted to the corresponding 3-arylisoxazolin-4-one oximes 8, by the action of concentrated alkali hydroxides or alkoxides (Scheme 6.1). 

Nearly ail aromatic azoxy compds crystallize well they are completely stable (ncunrHc strong HC but if warmed with coned H2S04 they undergo rearrangement. The true structure of azoxy compds was revealed by A. Angeli s discovery of isomerism in azoxy compds ... 

For four of the reactions shown in Tabled (entries 1, 5,11, and 12), absolute configuration correlations were established between the reactant and its solid-state photoproduct. Such correlations represent one of the most powerful methods available to the organic chemist for elucidating reaction mechanisms. In the NorrishA ang type II reaction (entries 1 and 5), for example, it allows an unequivocal determination of which y-hydrogen is abstracted, and for the di-ir-methane rearrangement of dibenzobarrelene derivatives (entries 11 and 12), it tells us precisely which atoms are involved in the formation of the initial cyclopropyldi-carbinyl diradical. 

ALPER Carbonylatton 2 AMADORI Glucosamine rearrangement 3 ANGELI - RtMINI Hydroxamc acid synthesis 4 ARBUZOV - MICHAELIS Phosphonate synthesis 5... 

Piperidine allowed to react with 2-acetylfuran in the presence of a catalytic amount of glacial acetic acid, and distilled o-(N-piperidyl) phenol. Y 65%. — The rearrangement occurs during distillation of the intermediate enamine. F. e. s. L. Birkofer and G. Daum, Ang. Ch. 72, 707 (1960) B. 95, 183 (1962). 

Contrary to what has been conveyed by historians, AngeU and his former teacher Ciamician possessed markedly different characters and temperaments, but nonetheless Ciamician never had a more faithful disciple and staunch supporter. Angeli even argued on his behalf with the doyen of Italian chemists, Stanislao Cannizzaro (1826-1910). He also had a few contretemps with Ferdinand Tiemann (1848-99), co-discoverer of the Reimer-Tiemann reaction and with Theodor Curtius (1857-1928), discoverer of the Curtius rearrangement, diazoacetic acid, and hydrazine. All of their discussions were conducted with great respect and mutual regard. 

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