Aus dem physikalisch-chemischen Laboratorium der Wiener Universit~it).

A series of 3-aroyl-2-arylaziridines underwent 1,3-dipolar cycloadditions in both orientations to the nitrogen-oxygen bond of 1-nitroso-2-naphthol. Spontaneous 1,3-cleavage of the intermediate oxadiazolidines to nitrones and cyclodehydration of the latter afforded both 2-aryl-and 2-aroylnaphtho-[1,2-d]oxazoles in good yields. The interpretation of the reaction received confirmation by independent, unambiguous synthesis of several 2-aroylnaphtho[l,2-d]oxazoles.Canadian Journal of Chemistry, 48, 2227Chemistry, 48, (1970 The thermal and photochemical cleavage of the carbon-carbon bond in aziridines to yield azomethine ylides and their subsequent [2 + 31 cycloaddition to reactive carbon-carbon multiple bonds, has been firmly established by several authors (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14).An interest in the general problem of synthesizing five and six membered ring heterocycles from the addition reactions of readily available small ring heterocycles led us to explore the analogous thermally induced additions of 3-aroylaziridines to heteromultiple bonds. We have reported the additions of 3-aroylaziridines and 3-carboalkoxyaziridines to the following heteromultiple bonds as dipolarophiles, (i) the C=S bond of aryl isothiocyanates with the formation of 4-aroyl-5-arylamino-4-thiazolines (15), (ii) the C=N bond of imines and sulfonylimines with the formation of imidazolidines (16), (iii) the C=O bond of diphenylcyclopropenone which ultimately affords 4-aroyl-4-oxazolines (17, 18), (iv) the C=O bond of aryl aldehydes and chloral to form oxazolidines (19), and (v) the C=N bond of cyclopropenimines to form imidazolines and imidazolidines (20).We report full details of an examination of the 1,3-dipolar cycloaddition of 3-aroylaziridines to the N=O bond of isomeric nitrosonaphthols which produced substituted naphtho[l,2-dloxazoles and which in the case of l-nitroso-2-naphthol provided compelling evidence for a concerted cycloaddition. These results have previously been published only in a preliminary form (21).Treatment of 3-benzoyl-l-cyclohexyl-2-pnitrophenylaziridine (22) The neighboring hydroxyl groups in 5 and 6 cyclize to the polarized azomethine bond with loss of water to produce 2 and 1 respectively. The secondary products of the 1,3-cleavage of the oxadiazolidines, which were expected to be the Schiff bases, could not be isolated. It has been our experience however that Schiff bases of Can. J. Chem. Downloaded from www.nrcresearchpress.com by 18.236.198.91 on 05/10/18For personal use only.

3-Aroylaziridines react with a variety of i~nines and aryl-N-sulfonylimines in ~.efluxing benzene to give imidazolidines in excellent yield. T h e orientation of the [2 + 31 cycloaddition of the intermediate azoniethine ylids to the C=;;N double bond was proven by synthesis of specifically 5-deuterated inlidazolidines. The reactions provide a convenient new general synthesis of imidazolidines.Canadian Journal of Chemistry. 47, 4335 (1969) Many substituted aziridines will undergo thermal cleavage ofthe 2-3 bond to an azometliine ylid intermediate, and subsequent [2 + 31 cycloaddition can take place to the acetylenic bond and to activated alkenes, in many and stereospecifically (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14).W e have reported the analogous thermally induced additions of 3-aroylaziridines to the polarized carbonyl bond of diphenylcyclopropenone with the formation of 4-aroyl-4-oxazolines (15) and to the C=S double bond of aryl isothiocyanates t o form 4-aroyl-5-arylimino-4-thiazolines (16). In a continuing study of these additions to heteromultiple bonds, we report the [2 + 31 cycloaddition of 3-aroylaziridines to activated imino con~pounds which provides a new synthesis of imidazolidines.Treatment of 3-benzoyl-1-isopropyl-2-phenylaziridine with an equimolar quantity of benzalaniline in refl~~xing toluene for 16 h, followed by chromatographic separation on alumina aKorded the imidazolidine 1 as a white crystalline solid in 24 "/,yield, m.p. 182". The nuclear magnetic resonance (11.m.r.) spectrum of 1 shows the isopropyl methyl groups are non-equivalent, indicating proxinlity to an asymmetric center in accordance with the proposed structure. While the initial product consisted of an isomeric mixture corresponding to cis and trans arrangement of protons at the 4 and 5 positions as shown by the 1l.m.r. spectrum, only the isomer described above could be obtained in solid form. This was assigned the cis geometry at the 4,5 positions on the basis of an 8 Hz c o~~p l i n g constant for the AB P~+ N /~H H I COAr R

2-Arenoylaziridines undergo thermal 1.3-dipolar addition to aromatic aldehydes and chloral via azomethine ylides to give exclusively 4-arenoyloxazolidines. Proof of the orientation of the addition was obtained and the formation of an alternative ring-expansion product was excluded by specific deuterium-labelling experiments. The lack of dependence of the course of the reaction on the stereochemistry of the aziridine, and the observed lack of basecatalysed epimerisation of the oxazolidines, suggested exclusive formation of the oxazolidines via the more stable trans-azomethine ylide and allowed an assignment of the full stereochemistry of the products.ADDITION reactions of substituted aziridines involving cleavage of the 2,3-bond to give an azomethine ylide intermediate and subsequent [2 + 31 cycloaddition to an acetylenic bond and to activated alkenes are synthetically useful routes to pyrroles and pyrrolines.l-14 Heat e.g. ArCH-CHAr

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