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Volumn 52, Issue 40, 2011, Pages 5153-5156

Comparing and taming the reactivity of HWE and Wittig reagents with cyclic hemiacetals

Author keywords

Lactols; Oxa Michael cyclisation; Wittig and HWE reactions

Indexed keywords

4 HYDROXY 2 METHYLPENTANAL; ACETAL DERIVATIVE; CARBOXYL GROUP; MORPHOLINE AMIDE PHOSPHORANE; MORPHOLINE DERIVATIVE; PHOSPHORANE DERIVATIVE; REAGENT; TETRAHYDROFURAN DERIVATIVE; TRIFLUOROETHANOL; UNCLASSIFIED DRUG;

EID: 80052324265     PISSN: 00404039     EISSN: 18733581     Source Type: Journal    
DOI: 10.1016/j.tetlet.2011.07.121     Document Type: Article
Times cited : (4)

References (51)
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    • 3 in agreement with: S.-K. Kang, and D.-H. Lee Synlett 1991 175 176 Reduction with DIBALH in THF at -78 °C afforded the lactol (1′/1″) in good yield
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    • for the easier cyclisation of a syn-1,3-dimethyl hydroxycarboxyl derivative, see: G. Mas, L. Gonzlez, and J. Vilarrasa Tetrahedron Lett. 44 2003 8805 8809
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    • a value in DMSO of 18.6. It means that the basicity of the HWE reagent (the anion) is ca. 10 units stronger than that of the sW reagent. See: C. Qi, Y. Du, Y. Lu, X. Sun, and X.-M. Zhang J. Org. Chem. 74 2009 8078 8085
    • (2009) J. Org. Chem. , vol.74 , pp. 8078-8085
    • Qi, C.1    Du, Y.2    Lu, Y.3    Sun, X.4    Zhang, X.-M.5
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    • also see: http://www.chem.wisc.edu/areas/reich/pkatable/kaphos.gif.
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    • One oxolane stereoisomer was formed mainly in each case, as depicted in Table 1, with the side chain at C2 and Me at C3 in trans. Ratios 3a/3a′ and 3d/3d′ were between 90:10 and 95:5. The relative configuration of 3a was assigned by NOESY experiments and by comparison with available NMR data of very similar structures: M.F. Semmelhack, and N. Zhang J. Org. Chem. 54 1989 4483 4485
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    • for the relative nucleophilicities of P-stabilised carbanions, see: R. Appel, R. Loos, and H. Mayr J. Am. Chem. Soc. 131 2009 704 714
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    • also see the following papers and references therein: L.K. Blasdel, and A.G. Myers Org. Lett. 7 2005 4281 4283 (use of fluorinated alkoxides)
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    • An alternative approach may be suggested, based on a suitable opening of lactol 1′/1″, followed by the protection of the hydroxy group and a standard HWE reaction with the CHO group once deprotected, but it meant additional synthetic steps. The direct protection of the hydroxy group is sometimes appropriate for lactols not substituted at C5, the open form of which is a more reactive primary alcohol (in general, when the OH group of the open form is less congested than the OH group of the lactol): E.K. Yau, and J.K. Coward J. Org. Chem. 55 1990 3147 3158
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    • T.J.A. Graham, E.E. Gray, J.M. Burgess, and B.C. Goess J. Org. Chem. 75 2010 226 228 However, in the case of 1′/1″, different attempts (with LiHMDS in THF at -78 °C followed after equilibration by addition of TBSCl and warming up to rt, with LiHMDS and TBSCl by direct mixing in THF at rt, with KHMDS at -78 °C and heating later at 60 °C with TBDPSCl) led to the TBS- or TBDPS-protected cyclic form (lactol) as the major product
    • (2010) J. Org. Chem. , vol.75 , pp. 226-228
    • Graham, T.J.A.1    Gray, E.E.2    Burgess, J.M.3    Goess, B.C.4
  • 40
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    • for illustrative lactol openings of simple C4-substituted derivatives, see: W.R. Roush, H.R. Gillis, and A.I. Ko J. Am. Chem. Soc. 104 1982 2269 2283
    • (1982) J. Am. Chem. Soc. , vol.104 , pp. 2269-2283
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    • We have been unable to find examples of opening of five-membered lactols with such a phosphorane, but there is one from a six-membered lactol: S. Nakamura, J. Inagaki, T. Sugimoto, Y. Ura, and S. Hashimoto Tetrahedron 58 2002 10375 10386
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    • Besides, the E selectivity is higher. The trend of the Weinreb amides of sW, HWE and Ando reagents to afford higher selectivities than the corresponding E or Z esters is known: K. Ando, S. Nagaya, and Y. Tarumi Tetrahedron Lett. 50 2009 5689 5691 and Ref. 10 cited therein; morpholine amides of Ando reagents also give higher Z/E ratios
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    • Ando, K.1    Nagaya, S.2    Tarumi, Y.3


* 이 정보는 Elsevier사의 SCOPUS DB에서 KISTI가 분석하여 추출한 것입니다.