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Synlett
Volumn , Issue 14, 2007, Pages 2217-2221
Improved and practical procedures for the preparation of highly substituted pyridines and pyridazines via silica-mediated aromatisation
Author keywords

Diels Alder reaction; Fused ring systems; Heterocycles; Pyridazines; Pyridines; Silica mediated aromatization
Indexed keywords

DIHYDROPYRIDINE; PYRIDAZINE DERIVATIVE; PYRIDINE DERIVATIVE; SILICA GEL;
EID: 34548705340     PISSN: 09365214     EISSN: None     Source Type: Journal    
DOI: 10.1055/s-2007-984918     Document Type: Article
Times cited : (25)
References (28)
  • 1
    • 28444462477 scopus 로고    scopus 로고
    • For recent references, see: a
    • For recent references, see: (a) Bagley, M. C.; Glover, C. Tetrahedron 2006, 62, 66.
    • (2006) Tetrahedron , vol.62 , pp. 66
    • Bagley, M.C.1    Glover, C.2
  • 9
  • 21
    • 34548741742 scopus 로고    scopus 로고
    • Representative Procedure A suspension of triazine 1a (50 mg, 0.21 mmol), pyrrolidine (6, 26 μL, 0.31 mmol), cyclopentanone (2a, 27 μL, 0.31 mmol) and silica (Fluka, flash chromatography silica gel 60, 220-440 mesh, 200 mg) in toluene (4 mL) was heated under reflux for 5 h. The reaction mixture was cooled to r.t., diluted with EtOAc (6 mL), and stirred an additional 20 min at the same temperature. The mixture was then filtered through a Celite pad, concentrated and the residue obtained was eluted from a column of silica (PE-EtOAc, 5:1) yielding the desired pyridine 5a (57 mg, 99%); data were consistent with those reported in ref. 2b.
    • Representative Procedure A suspension of triazine 1a (50 mg, 0.21 mmol), pyrrolidine (6, 26 μL, 0.31 mmol), cyclopentanone (2a, 27 μL, 0.31 mmol) and silica (Fluka, flash chromatography silica gel 60, 220-440 mesh, 200 mg) in toluene (4 mL) was heated under reflux for 5 h. The reaction mixture was cooled to r.t., diluted with EtOAc (6 mL), and stirred an additional 20 min at the same temperature. The mixture was then filtered through a Celite pad, concentrated and the residue obtained was eluted from a column of silica (PE-EtOAc, 5:1) yielding the desired pyridine 5a (57 mg, 99%); data were consistent with those reported in ref. 2b.
  • 23
    • 34548710268 scopus 로고    scopus 로고
    • Similar reactions were carried out in which the silica gel was replaced by stoichiometric amounts of HCl, MeCOOH, Et3N, or 1,5-diazabicyclo[4.3.0]non-5-ene DBU, None of these reactions produced pyridines 5 in significant quantities
    • 3N, or 1,5-diazabicyclo[4.3.0]non-5-ene (DBU). None of these reactions produced pyridines 5 in significant quantities.
  • 27
    • 34548745776 scopus 로고    scopus 로고
    • The structure of the cycloaddition product 10 was assigned using NOE and HMBC NMR experiments.
    • The structure of the cycloaddition product 10 was assigned using NOE and HMBC NMR experiments.
  • 28
    • 34548768214 scopus 로고    scopus 로고
    • A solution of triazine 1a (100 mg, 0.43 mmol, pyrrolidine (6, 52 μL, 0.64 mmol) and estrone (9, 113 mg, 0.42 mmol) in xylene (4 mL) was heated in a screwcapped tube at 160°C for 10 h. The reaction mixture was cooled to r.t, silica (Fluka, flash chromatography silica gel 60, 220-440 mesh) was added and the yellow suspension obtained refluxed for an additional 5 h. The mixture was then cooled to r.t, filtered through a Celite pad, concentrated and the residue obtained was eluted from a column of silica (CHCl3-EtOAc, 7:1) yielding the desired 3-hydroxy-estra-1,3,5 (10)-triene-[17,16-c, 2′-pyrid-2-yl, 6′-phenyl, pyridine(10, 129 mg, 67, as a white solid, mp 261-262°C (toluene-hexane, α]D25 -50.0 (c 0.5, CHCl3, 1H NMR (400 MHz, CDCl3, δ, 8.71 (1 H, ddd, J, 0.9, 1.8, 4.8 Hz, C-9′-H, 8.43 1 H, ddd, J, 0.9, 1.0, 7.9 Hz, C-1
    • 2O [M + 1]: 459.2436; found: 459.2431 (-3.2 ppm error).

* 이 정보는 Elsevier사의 SCOPUS DB에서 KISTI가 분석하여 추출한 것입니다.