Among the three types of dihydro derivatives of isoxazoles, 2-isoxazolines have been studied in detail but only recently have a limited number of 4-isoxazolines become available. The latter system has been synthesized mainly by the 1,3-cftpolar cycloaddition reaction of nitrones with acetylene carboxylates (1). Little was known about the 3-isoxmoline system prior to our proceeding paper (2), in which we reported that some 5-unsubstituted isoxazolium salts u react with Grignard reagents to give 5-substituted I-isoxazoline derivatives (2). We now wish to report a new synthesis of bisoxazoline derivatives w from 3-unsubstituted isoxazole quaternary salk w); and the thermal conversion of I-bemyl-bisoxazoline derivatives into pyrrole derivatives. Reaction of 2,4-dimethyl+phenylisoxazolium perchlorate w with methylmagneium iodide in ether at 0" gave an oil w together with the ring cleavage product, 2-beruoyl-3-methylamino-2-butene w. The oily product& was purified only by chromatogmphy through alumina because of ik instability. Formulation of & as 2,3,4-trimethyl-5-phenyl-4-isoxazoline follows from ik elementary analysis (3) and spectml data (see TABLE I). Further evidence for the structure && was obtained by catalytic reduction with Raney nickel, which afforded a mixture of 2-bemoyl-2-butene @ and a-ethylpropiophenone 0. The structure assigmnent for2 was supported by ik elementary analyris (3), spectral properties and reaction with hydrazine hydmte, which gave 3,4-dimethyl-S-phenylpyrazole @,. would undergo cleavage of the C-C bond to give the aminoketone @, dehydrative ring closure of which would give the final product 2. An analogous thermal rearrangement of some 4-isoxazolines to 2-acylaziridines has been described by Baldwin et al. (6). However, their final products are the corresponding 4oxozoli nes . Only two examples (l3_and 3 of pvle formation similar to our present case have been reported by Aceson et al. (7) and Winterfeldt et al. (8).
The scope and limitations of the new reaction described in this paper are under investigation.
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