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Methods of Organic Chemistry (Houben-Weyl); de Meijere, A., Ed.; Thieme: Stuttgart, Germany, 1997; E17a-d.
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(c) Methods of Organic Chemistry (Houben-Weyl); de Meijere, A., Ed.; Thieme: Stuttgart, Germany, 1997; Vol. E17a-d.
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(c) Goti, A.; Cordero, F. M.; Brandi, A. Top. Curr. Chem. 1996, 178, 1.
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Reviews: (a) de Meijere, A.; Kozhushkov, S. I.; Khlebnikov, A. F. Top. Curr. Chem. 2000, 207, 89.
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(b) de Meijere, A.; Kozhushkov, S. I.; Khlebnikov, A. F. Zh. Org. Khim. 1996, 32, 1607;
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de Meijere, A.1
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(a) Diev, V. V.; Kostikov, R. R.; Gleiter, R.; Molchanov, A. P. J. Org. Chem. 2006, 71, 4066.
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Molchanov, A.P.4
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3242751982
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(b) Molchanov, A. P.; Diev, V. V.; Kopf, J.; Kostikov, R. R. Russ. J. Org. Chem (Engl. Transl.) 2004, 40, 431.
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Russ. J. Org. Chem (Engl. Transl.)
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Molchanov, A.P.1
Diev, V.V.2
Kopf, J.3
Kostikov, R.R.4
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For reviews on the 1,3-dipolar cycloaddition of nitrones, see: a, Padwa, A, Pearson, W. H, Eds, Wiley: New York
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For reviews on the 1,3-dipolar cycloaddition of nitrones, see: (a) Jones, R. C. F.; Martin, J. N. In Synthetic Application of 1,3-Dipolar Cycloaddition Chemistry Toward Heterocycles and Natural Products; Padwa, A., Pearson, W. H., Eds.; Wiley: New York, 2002; pp 1-81.
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Synthetic Application of 1,3-Dipolar Cycloaddition Chemistry Toward Heterocycles and Natural Products
, pp. 1-81
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Jones, R.C.F.1
Martin, J.N.2
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0002108906
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Padwa, A, Ed, Wiley: New York
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(c) Tufariello, J. J. In 1,3-Dipolar Cycloaddition Chemistry; Padwa, A., Ed.; Wiley: New York, 1984; Vol. 2, pp 83-168.
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(1984)
1,3-Dipolar Cycloaddition Chemistry
, vol.2
, pp. 83-168
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Tufariello, J.J.1
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41849090023
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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
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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.
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1 of nitrones can occur in exo transitional state (exo-TS): (Chemical Equation Presented)
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1 of nitrones can occur in exo transitional state (exo-TS): (Chemical Equation Presented)
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23
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41849098486
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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
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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.
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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
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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)
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41849132069
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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.
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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.
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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
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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.
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0035858655
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For recent examples of closely related isomerization of 4-isoxazolines to aziridines, see: a
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For recent examples of closely related isomerization of 4-isoxazolines to aziridines, see: (a) Friebolin, W.; Eberbach, W. Tetrahedron 2001, 57, 4349.
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(2001)
Tetrahedron
, vol.57
, pp. 4349
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Friebolin, W.1
Eberbach, W.2
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(b) Ishikawa, T.; Kudoh, T.; Yoshida, J.; Yasuhara, A.; Manabe, S.; Saito, S. Org. Lett. 2002, 4, 1907.
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(2002)
Org. Lett
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Ishikawa, T.1
Kudoh, T.2
Yoshida, J.3
Yasuhara, A.4
Manabe, S.5
Saito, S.6
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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;
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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;
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Russ. J. Org. Chem. (Engl. Transl.) 1975, 11, 1333. In addition, analogous ketones have been reported in this work.
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Russ. J. Org. Chem. (Engl. Transl.) 1975, 11, 1333. In addition, analogous ketones have been reported in this work.
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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
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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.
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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.
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(c) For recent review on conjugated azomethine ylides, see: Pinho e Melo, T. M. V. D. Eur. J. Org. Chem. 2006, 2873.
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For review on 1,5-dipolar cyclizations. see
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(d) For review on 1,5-dipolar cyclizations. see: Taylor, E. C.; Turchi, I. J. Chem. Rev. 1979, 79, 181.
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(1979)
Chem. Rev
, vol.79
, pp. 181
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Taylor, E.C.1
Turchi, I.J.2
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