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Volumn 73, Issue 6, 2008, Pages 2396-2399

Nitrone cycloadditions to 1,2-diphenylcyclopropenes and subsequent transformations of the isoxazolidine cycloadducts

Author keywords

[No Author keywords available]

Indexed keywords

CYCLOADDITION; PHASE TRANSITIONS; QUANTUM YIELD;

EID: 41849109877     PISSN: 00223263     EISSN: None     Source Type: Journal    
DOI: 10.1021/jo702379d     Document Type: Article
Times cited : (47)

References (34)
  • 3
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    • Methods of Organic Chemistry (Houben-Weyl); de Meijere, A., Ed.; Thieme: Stuttgart, Germany, 1997; E17a-d.
    • (c) Methods of Organic Chemistry (Houben-Weyl); de Meijere, A., Ed.; Thieme: Stuttgart, Germany, 1997; Vol. E17a-d.
  • 4
  • 21
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    • Chemistry of Heterocyclic Compounds Engl. Transl, 1982, 18, 910. In the reaction of C,N-diphenylnitrone with 1,3,3-trimethylcyclopropene, products were not identified: see ref 1h
    • Chemistry of Heterocyclic Compounds (Engl. Transl.) 1982, 18, 910. In the reaction of C,N-diphenylnitrone with 1,3,3-trimethylcyclopropene, products were not identified: see ref 1h.
  • 22
    • 41849147075 scopus 로고    scopus 로고
    • 1 of nitrones can occur in exo transitional state (exo-TS): (Chemical Equation Presented)
    • 1 of nitrones can occur in exo transitional state (exo-TS): (Chemical Equation Presented)
  • 23
    • 41849098486 scopus 로고    scopus 로고
    • Only one isomer of aziridines 4 was isolated from the reaction mixtures. For the most stable aziridine 4b, X-ray analysis did not give reliable result (R factor, 0.14; for a view, see Supporting Information, The obtained aziridine 4a appeared to be somewhat unstable in solutions in air, slowly furnishing the corresponding pyrrole 5a. However, the rather stable aziridine 4b can be obtained in the reaction of diarylnitrone 2b. The stability of aziridines was also found to be dependent on the nature of the substituent R in the α-position. Thus, the corresponding aziridine 4e formed in the reaction of 3-methyl-1,2- diphenylcyclopropene 1b (Table 1, entry 6) can only be detected by TLC. This aziridine underwent complete transformation to the pyrrole 5e on silica gel
    • Only one isomer of aziridines 4 was isolated from the reaction mixtures. For the most stable aziridine 4b, X-ray analysis did not give reliable result (R factor = 0.14; for a view, see Supporting Information). The obtained aziridine 4a appeared to be somewhat unstable in solutions in air, slowly furnishing the corresponding pyrrole 5a. However, the rather stable aziridine 4b can be obtained in the reaction of diarylnitrone 2b. The stability of aziridines was also found to be dependent on the nature of the substituent R in the α-position. Thus, the corresponding aziridine 4e formed in the reaction of 3-methyl-1,2- diphenylcyclopropene 1b (Table 1, entry 6) can only be detected by TLC. This aziridine underwent complete transformation to the pyrrole 5e on silica gel.
  • 24
    • 41849119047 scopus 로고    scopus 로고
    • Besides ketones, products of decomposition of Schiff bases were formed (corresponding aldehydes) as well as compounds A-F (see Supporting Information, The latter are products of the 1,3-dipolar cycloaddition of nitrones to the double C,C bond of the initially formed unsaturated ketones. Dipolar cycloadditions with different unsaturated carbonyl compounds are well documented see ref 5, Chemical Equation Presented
    • Besides ketones, products of decomposition of Schiff bases were formed (corresponding aldehydes) as well as compounds A-F (see Supporting Information). The latter are products of the 1,3-dipolar cycloaddition of nitrones to the double C,C bond of the initially formed unsaturated ketones. Dipolar cycloadditions with different unsaturated carbonyl compounds are well documented (see ref 5). (Chemical Equation Presented)
  • 25
    • 41849132069 scopus 로고    scopus 로고
    • Taking into account that the two isomeric products 9 can be obtained from a single isomer of 8, the initial formation of two isomeric cyclopropenyl isoxazolidines 8 can be proposed. Only the more stable isomer was isolated.
    • Taking into account that the two isomeric products 9 can be obtained from a single isomer of 8, the initial formation of two isomeric cyclopropenyl isoxazolidines 8 can be proposed. Only the more stable isomer was isolated.
  • 26
    • 41849118695 scopus 로고    scopus 로고
    • According to B3LYP/6-31G* calculations, the terminal vinylic carbon atom of 3-vinyl-1,2-diphenylcyclopropene 1f has the greatest negative charge, 0.3, Lowdin, The charges on another vinylic carbon atom and carbons of the cyclopropenyl double bond are close to 0. Remarkably, carbonyl ylide cycloadditions to cyclopropene 1f proceed to the C,C double bond of the three-membered ring (see ref 4, Also, we can suggest that the difference between steric screening of double bonds in both synclinal and periplanar conformations of vinylcyclopropene 1f (see Supporting Information) is not enough to explain regiochemical outcome of the reaction
    • According to B3LYP/6-31G* calculations, the terminal vinylic carbon atom of 3-vinyl-1,2-diphenylcyclopropene 1f has the greatest negative charge (-0.3, Lowdin). The charges on another vinylic carbon atom and carbons of the cyclopropenyl double bond are close to 0. Remarkably, carbonyl ylide cycloadditions to cyclopropene 1f proceed to the C,C double bond of the three-membered ring (see ref 4). Also, we can suggest that the difference between steric screening of double bonds in both synclinal and periplanar conformations of vinylcyclopropene 1f (see Supporting Information) is not enough to explain regiochemical outcome of the reaction.
  • 27
    • 0035858655 scopus 로고    scopus 로고
    • For recent examples of closely related isomerization of 4-isoxazolines to aziridines, see: a
    • For recent examples of closely related isomerization of 4-isoxazolines to aziridines, see: (a) Friebolin, W.; Eberbach, W. Tetrahedron 2001, 57, 4349.
    • (2001) Tetrahedron , vol.57 , pp. 4349
    • Friebolin, W.1    Eberbach, W.2
  • 29
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    • For reviews on N-O bond cleavage in nitrone-alkylidenecyclopropane cycloadducts, see ref 2. For closely related N-O bond cleavage in nitrile oxide-cyclopropene cycloadducts, see: Zaitseva, L. G, Chizhov, I. G, Bolesov, I. G. Zh. Org. Khim. 1975, 11, 1347;
    • For reviews on N-O bond cleavage in nitrone-alkylidenecyclopropane cycloadducts, see ref 2. For closely related N-O bond cleavage in nitrile oxide-cyclopropene cycloadducts, see: Zaitseva, L. G.; Chizhov, I. G.; Bolesov, I. G. Zh. Org. Khim. 1975, 11, 1347;
  • 30
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    • Russ. J. Org. Chem. (Engl. Transl.) 1975, 11, 1333. In addition, analogous ketones have been reported in this work.
    • Russ. J. Org. Chem. (Engl. Transl.) 1975, 11, 1333. In addition, analogous ketones have been reported in this work.
  • 31
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    • Note the proposed mechanism needs more clarification. Thus, it is problematic to demonstrate whether enolization of azomethine ylide or direct intramolecular nucleophilic addition occurs (route 1 vs 2, For the possibility of conversion of aziridines to pyrroles via 1,5-electrocyclization of transient azomethine ylide, see: (a) Padwa, A, Dean, D, Mazzu, A, Vega, E. J. Am. Chem. Soc. 1973, 95, 7168
    • Note the proposed mechanism needs more clarification. Thus, it is problematic to demonstrate whether enolization of azomethine ylide or direct intramolecular nucleophilic addition occurs (route 1 vs 2). For the possibility of conversion of aziridines to pyrroles via 1,5-electrocyclization of transient azomethine ylide, see: (a) Padwa, A.; Dean, D.; Mazzu, A.; Vega, E. J. Am. Chem. Soc. 1973, 95, 7168.
  • 33
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    • For recent review on conjugated azomethine ylides, see: Pinho e Melo, T. M. V. D. Eur. J. Org. Chem. 2006, 2873.
    • (c) For recent review on conjugated azomethine ylides, see: Pinho e Melo, T. M. V. D. Eur. J. Org. Chem. 2006, 2873.
  • 34
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    • For review on 1,5-dipolar cyclizations. see
    • (d) For review on 1,5-dipolar cyclizations. see: Taylor, E. C.; Turchi, I. J. Chem. Rev. 1979, 79, 181.
    • (1979) Chem. Rev , vol.79 , pp. 181
    • Taylor, E.C.1    Turchi, I.J.2


* 이 정보는 Elsevier사의 SCOPUS DB에서 KISTI가 분석하여 추출한 것입니다.