424. Experiments towards the synthesis of corrins. Part III. Formation of a bicyclic oxaziran from a Δ¹-pyroline and from the corresponding nitrone

Abstract

Irradiation of 5 : 5-dimethyl-Al-pyrroline 1 -oxide yields the bicyclic oxaziran (IV), also obtained by oxidation of 5 : 5-dimethylpyrroline with aqueous hydrogen peroxide. Thermal rearrangement of the oxaziran (IV) leads to 5 : 5-dimethylpyrrolid-2-oneJ whereas acidic hydrolysis yields laevulic aldehyde.Investigation of a reported 3-hydroxyoxaziran shows it to be the isomeric hydroxamic acid. RECENT investigations l s 2 have revived interest in compounds containing the threemembered carbon-nitrogen-oxygen (oxaziran) ring (I) , a formulation at one time suggested for the nitrones (azomethine N-oxides) (11) only to be subsequently discarded. The oxazirans and the azomethine N-oxides might be regarded as electronic tautomers and, indeed, irradiation of nitrones can yield o x a ~i r a n s , ~ thermal decomposition of which regenerates the original n i t r ~n e s . ~In the course of our work on Al-pyrroline l-oxides we irradiated 5 : 5-dimethyl-A1pyrroline l-oxide 5 (111), whereupon the nitrone was converted into an isomer to which we assign the oxaziran structure (IV). The same material was obtained on oxidation of 5 : 5-dimethyl-Al-pyrroIine with aqueous hydrogen peroxide.The product is assigned structure (IV) on the basis of its analysis and active-oxygen content (cf. ref. l ) , and the absence of ultraviolet absorption (in ethanol), of infrared maxima (liquid film) in the N-H and double-bond regions, and of basic properties. The * Part 11, preceding paper.

A Computational Study on the Photochemistry of 2,4,4‐Trimethyl‐1‐pyrroline 1‐Oxide and Investigation on the Reaction Paths of Its Photoproduct Oxaziridine

“…A high energy barrier was required to form lactam through breaking of the C–CH 3 bond adjacent to the nitrogen. These results supported the experimental observations of Todd group and Lamchen group, reported almost sixty years back. The latter group carried out photo‐irradiation and pyrolysis studies on several other cyclic nitrone systems, as well.…”

2-ethoxycarbonyl-2-methyl-3,4-dihydro-2H-pyrrole-1-oxide: evaluation of the spin trapping properties

“…The synthesis of nitrone 5 was first reported by Bonnett [13]. In the present work, we used a modified procedure as presented in scheme 2.…”

Studies in the Pyrroline Series: V. 3,3-Dimethyl-1-Pyrroline-1-Oxide

“…For comparison, 5,5-dimethyl-1-pyrroline-1-oxide has A, , , 234 mp (log e 3.89) in ethanol (8) and A, , , 247 mp (log E 3.94) in hexane. Ultraviolet irradiation produced a considerable decrease in absorption in all cases, presumably as a result of oxaziran formation (9). These results indicated that the base probably had structure I11 or IV, or could possibly be a mixture of the two.…”