Thermal [2 + 3] cycloaddition of imino compounds to 3-aroylaziridines. Synthesis of imidazolidines

Abstract

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

Thermal [2 + 3] cycloaddition of N-trichloroacetyldiphenylcyclopropenimine to 3-aroylaziridines and 3-carbomethoxyaziridines

“…Similar lack of stereospecificity with respect to the aziridine was observed in the addition of cis-and trans-2-aryl-3-aroylaziridines (with N-alkyl substituents) to imines and sulfonylimines to form imidazolidines (11) and to aryl aldehydes and chloral to form oxazolidines (8). This may be attributed to equilibration of the cis-and trans-azomethine ylide intermediates (22) (derived from the thermal conrotatory ring opening of the trans-and cisaziridines respectively (5)) prior to addition leading to 1,3-dipolar addition exclusively via the more stable trans-azomethine ylide (22).…”

Thermal Decomposition of Stereoisomeric 3-Aroyl- and 3-Carbomethoxyaziridines in Acetonitrile

“…It is noteworthy that in the experiments involving deuterium labelled aziridines in acetonitrile in this study, quantitative transfer of the deuterium was often observed. This is in contrast to previous work in nonpolar solvents where appreciable leakage of deuterium label was observed (10,(13)(14)(15)(16).…”

Synthesis and cycloaddition reactions of 2-(2-thienyl)aziridines

“…trans-2-aryl-3-aroylaziridines (with N-alkyl substituents) to imines (6), sulfonylimines (6), and iminocyclopropenes (7) to give imidazolidines and to aryl aldehydes and chloral to give oxazolidines (10). We conclude that the prior equilibration of the cis and trans azomethine ylides (21) (from conrotatory thermal ring opening of the trans and cis aziridines respectively (22)) occurs and addition takes place exclusively via the more stable trans azomethine ylide.…”