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Volumn 61, Issue 17, 2005, Pages 4261-4274

Dialkylzinc mediated radical additions to chiral N-enoyloxazolidinones in the presence of benzaldehyde. Mechanistic investigation, structural characterization of the resulting γ-lactones

Author keywords

Diethylzinc; N Enoyloxazolidinones; Radical polar crossover reaction; Lactones

Indexed keywords

BENZALDEHYDE; DIISOPROPYLZINC; FUMARIC ACID; GAMMA LACTONE DERIVATIVE; IODIDE; IODINE; N ENOYLOXAZOLIDINONE; OXAZOLIDINONE DERIVATIVE; UNCLASSIFIED DRUG; ZINC DERIVATIVE;

EID: 16244417479     PISSN: 00404020     EISSN: None     Source Type: Journal    
DOI: 10.1016/j.tet.2005.02.042     Document Type: Article
Times cited : (59)

References (47)
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    • (1991) Tetrahedron , vol.47 , pp. 2821-2834
    • Ito, Y.1    Terashima, S.2
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    • For triethylborane mediated tandem addition to enone/aldol condensation see: (a) K. Nozaki, K. Oshima, and K. Utimoto Tetrahedron Lett. 29 1988 1041 1044
    • (1988) Tetrahedron Lett. , vol.29 , pp. 1041-1044
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    • For a general review on organoboranes in radical chemistry see: (f) C. Ollivier, and P. Renaud Chem. Rev. 101 2001 3415 3434
    • (2001) Chem. Rev. , vol.101 , pp. 3415-3434
    • Ollivier, C.1    Renaud, P.2
  • 19
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    • note
    • 3B behave differently might be related to the chelating character of diethylzinc which would induce an increase of the spin density at the oxygen atom. Alternatively, homolytic substitution at zinc might have a lower activation energy, allowing the reaction to proceed with radicals having a spin density at oxygen lower than enoxyl radicals.
  • 24
    • 0032960346 scopus 로고    scopus 로고
    • For a general review on conjugate radical additions see: (a) M. Sibi, and N.A. Porter Acc. Chem. Res. 32 1999 163 171
    • (1999) Acc. Chem. Res. , vol.32 , pp. 163-171
    • Sibi, M.1    Porter, N.A.2
  • 27
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    • note
    • At lower temperature the reaction was slowed down; it gave lower yields with no significant improvement of the selectivity.
  • 28
    • 85030794292 scopus 로고    scopus 로고
    • note
    • Reactions performed without adding oxygen in an undegassed solvent revealed much slower and gave very poor yields. Under carefully degassed conditions most of the starting material remained unchanged.
  • 29
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    • For general reviews on the synthesis and the reactivity of organozinc see: P. Knochel Synlett 1995 393 403
    • (1995) Synlett , pp. 393-403
    • Knochel, P.1
  • 32
    • 85030800791 scopus 로고    scopus 로고
    • note
    • According to Table 1, it can be noted that the carbonyl group bearing the auxiliary induces a deshielding of the cis protons. The deshielding effect is significant on H4 (0.20-0.23 ppm (cf. 3, 5 / 7), or 0.40-0.53 ppm (cf 19 / 20 or 15 / 17)), it is negligible on H2. H3 is shielded by 0.34-0.67 ppm by the syn alkyl group (cf. 3, 5 / 4, 6 or 15, 19 / 16, 18), it suffers a larger shielding effect from the syn phenyl group (1.03-1.08 ppm, (cf. 7 / 4, 6) or 0.83-1.11 ppm, (cf. 17, 20 / 16, 18)).
  • 35
    • 85030793536 scopus 로고    scopus 로고
    • note
    • The cleavage of a pure sample of 5, later obtained from substrate 2, confirmed that 5 did not lead to acid 8, but to a mixture of products containing another amide-alcohol 12b.
  • 36
    • 85030793608 scopus 로고    scopus 로고
    • note
    • -.
  • 37
    • 85030800640 scopus 로고    scopus 로고
    • note
    • 1H NMR from the integration of the overlapping AB parts of the ABX systems in each diastereomer.
  • 38
    • 85030796804 scopus 로고    scopus 로고
    • note
    • The tridimensional structure of 5 clearly reveals that both faces of the exocyclic carbonyl group are hindered and none can be attacked by the nucleophile.
  • 39
    • 85030802870 scopus 로고    scopus 로고
    • note
    • 1H NMR spectrum of the mixture after elimination of unreacted benzaldehyde by liquid chromatography.
  • 40
    • 85030795417 scopus 로고    scopus 로고
    • note
    • 1H NMR signals very close to those of 9 (cf. Table 1).
  • 41
    • 85030796650 scopus 로고    scopus 로고
    • note
    • It must be noted that in the NMR spectra of 13h (and 13c) and to a lesser extent the spectrum of 13d, the doublet corresponding to the vinylic proton and the signal of the corresponding carbon are broadened. This phenomenon is probably related to the rate of rotation around the C-N bond. Lowering the temperature at -10 °C afforded well resolved spectra and allowed to unambiguously establish the correlation between the protons and the corresponding carbons by HMQC.
  • 42
    • 85030801560 scopus 로고    scopus 로고
    • note
    • 34=11.4 Hz).
  • 43
    • 85030796074 scopus 로고    scopus 로고
    • note
    • 1H NMR spectrum of enriched chromatographic fractions clearly show the characteristic signals of the ethoxycarbonyl groups and the absence of the oxazolidinone protons (cf. Section 4.2.20).
  • 46
    • 85030804934 scopus 로고    scopus 로고
    • note
    • Supporting Information content: Chiral HPLC analyses of racemic and optically pure lactones 9 and 22 (S2-S5), of lactones 15, 16, 17, 18, 19 and 20 (S6), detailed chiral HPLC conditions (S7). Significant NOESY correlations for lactones 9 and 15-20 (S8).
  • 47
    • 85030795500 scopus 로고    scopus 로고
    • note
    • Crystallographic data (excluding structure factors) for the structures in this paper have been deposited with the Cambridge Crystallographic Data Centre as supplementary publication numbers CCDC 257463 for lactone 3, 257464 for lactone 4, 257465 for lactone 5, and 257466 for lactone 18. Copies of the data can be obtained, free of charge, on application to CCDC, 12 Union Road, Cambridge CB2 1EZ, UK [Fax: +44-(0)1223-336033 or e-mail: deposit@ccdc.cam.ac.uk ].


* 이 정보는 Elsevier사의 SCOPUS DB에서 KISTI가 분석하여 추출한 것입니다.