The synthesis of a monocyclic a-dinitrone, hexamethyl-2.3-dihydropyrazine 1.4-dioxide, and proof of its structure is described. Its following reactions are reported : reduction ; base-catalysed reaction with aromatic aldehydes and acrylonitrile ; oxidation with selenium dioxide ; attemptsd 1.3-cyclo-addition reactions ; and reaction with a Grignard reagent. These results indicate that typical nitrone reactions are here either absent or greatly depressed.

Ultraviolet irradiation of 2-substituted 1 -pyrroline 1 -oxides yielded corresponding bicyclic oxaziridines. Prolonged irradiation of the 3,3,5-trimethyl-6-oxa-l -azabicyclo[3.1 ,O] hexane gave an N-acetylazetidine and a pyrroline. Acid hydrolyses of 2,2,5and 3,3,5-trimethyl-6-oxa-l -azabicyclo[3,1 .O] hexane yielded acetonylacetone and 3.3-dimethylpentan-5-aI-2-one. respectively. The synthesis of the nitrone 3.35-trimethyl-1 -pyrroline 1 -oxide and its irradiation to form an oxaziridine is described. Prolonged irradiation of the latter yielded a pyrrolidinone.IRRADIATION of acyclic nitrones gives isomeric oxaziridines,2 but Todd and his co-workers3 reported that whilst irradiation of the cyclic nitrone 5,5-dimethyll-pyrroline l-oxide (Ia) produced the oxaziridine (IIa), irradiation of 2-substituted l-pyrroline l-oxides, e.g., (Ic) failed to yield oxaziridines.The reason was obscure, but is not electronic since the 2-substituted l-pyrroline l-oxides absorb strongly at almost the same ultraviolet wavelength and with the same intensity as the unsubstituted nitrones, so excitation of the x-electrons in the nitrone system must still occur. Molecular models show that a 2-methyl substituent does not appear to offer sufficient steric hindrance to prevent oxaziridine formation.With this in mind, 2,5,5-trimethyl-l-pyrroline l-oxide (Ib) was irradiated. In the solvent used by Todd and his co-workers (1 : 1 ethanol-cyclohexane) , overnight

Nitrones of the l-pyrroline l-oxide type undergo 1,3-cycloaddition with ethyl acrylate, acrylonitrile, and allyl alcohol. By using 5,5-dimethylpyrroline 1-oxide and ethyl acrylate, i t was shown that the orientation of addition was temperature-dependent, and the structures of the adducts formed a t room temperature and a t 100" have been determined. The results obtained can be accounted for in terms of the two possible modes of polarisation of the nitrone system. The structure of the allyl alcohol adduct has also been determined. Syntheses of 2-(5,5-dimethylpyrrolidin-2-yl)propane-1,3-diol and 3-(5,5-dimethylpyrrolidin-2-y1)propane-1,2-diol are described.THE reaction of nitrones with olefins to form isoxazolidines is well established.l.2 It is also known that the nitrone system (I) generally undergoes nucleophilic additions at the carbon atom and it thus must polarise as indicated in (a) to form the structure (Ia). (a) (I)Experimental evidence, however, indicates that under certain conditions back-polarisation, (b), to produce the structure (Ib) must take place.4

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