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1
-
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0027200955
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For a review that includes nucleophilic substitution on five-membered ring acetals, see: Harmange, J.-C.; Figadère, B. Tetrahedron: Asymmetry 1993, 4, 1711-1754.
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Harmange, J.-C.1
Figadère, B.2
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4
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0033616106
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Larsen, C. H.; Ridgway, B. H.; Shaw, J. T.; Woerpel, K. A. J. Am. Chem. Soc. 1999, 121, 12208-12209.
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J. Am. Chem. Soc.
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Larsen, C.H.1
Ridgway, B.H.2
Shaw, J.T.3
Woerpel, K.A.4
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5
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-
0034597491
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-
Five-membered ring iminium ions are believed to undergo nucteophilic attack by transition structures similar to those for oxocarbenium ions: Eur. S. K.; Martin, S. F. Org. Lett. 2000, 2, 3445-3447.
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Org. Lett.
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Bur, S.K.1
Martin, S.F.2
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9
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0033582751
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Dudley, T. J.; Smoliakova, I. P.; Hoffmann, M. R. J. Org. Chem. 1999, 64, 1247-1253.
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J. Org. Chem.
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Dudley, T.J.1
Smoliakova, I.P.2
Hoffmann, M.R.3
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13
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0001399973
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Ishihara, J.; Miyakawa, J.; Tsujimoto, T.; Murai, A. Synlett 1997, 1417-1419.
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Synlett
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Ishihara, J.1
Miyakawa, J.2
Tsujimoto, T.3
Murai, A.4
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14
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0034704624
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Yang, J.; Cohn, S. T.; Romo, D. Org. Lett. 2000, 2, 763-766.
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Org. Lett.
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Yang, J.1
Cohn, S.T.2
Romo, D.3
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15
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0242478525
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note
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Similarly, the minor product could arise from either outside attack on the diequatorial oxocarbenium ion 7 or inside attack on the diaxial cation 8.
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-
-
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18
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0033612214
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For a recent example that compares the stereoselectivity of constrained versus unconstrained five-membered ring oxocarbenium ions, see: Crich, D.; Hao, X. J. Org. Chem. 1999, 64, 4016-4024.
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J. Org. Chem.
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, pp. 4016-4024
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Crich, D.1
Hao, X.2
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24
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0033003099
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Ooi, T.; Tayama, E.; Yamada, M.; Maruoka, K. Synlett 1999, 729-730.
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Synlett
, pp. 729-730
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Ooi, T.1
Tayama, E.2
Yamada, M.3
Maruoka, K.4
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25
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0001161387
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Askin, D.; Volante, R. P.; Ryan, K. M. Tetrahedron Lett. 1988, 29, 4245-4248.
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(1988)
Tetrahedron Lett.
, vol.29
, pp. 4245-4248
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Askin, D.1
Volante, R.P.2
Ryan, K.M.3
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27
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0030973398
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(b) Matsutani, H.; Ichikawa, S.; Yaruva, J.; Kusumoto, T.; Hiyama, T. J. Am. Chem. Soc. 1997, 119, 4541-4542.
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J. Am. Chem. Soc.
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Matsutani, H.1
Ichikawa, S.2
Yaruva, J.3
Kusumoto, T.4
Hiyama, T.5
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28
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0000693134
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Other reactions of acetals do not appear to involve free cations: (c) Denmark, S. E.; Almstead, N. G. J. Am. Chem. Soc. 1991, 113, 8089-8110.
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J. Am. Chem. Soc.
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Denmark, S.E.1
Almstead, N.G.2
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29
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0242646925
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(a) ref 4
-
In our experiments with both tetrahydrofuran and tetrahydropyran acetals, the stereochemistry of nucleophilic substitution was independent of the anomer ratios of the starting acetates: (a) ref 4.
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-
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30
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0034639452
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(b) Romero, J. A. C.; Tabacco, S. A.; Woerpel, K. A. J. Am. Chem. Soc. 2000, 122, 168-169.
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J. Am. Chem. Soc.
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Romero, J.A.C.1
Tabacco, S.A.2
Woerpel, K.A.3
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31
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0032557195
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Burfeindt, J.; Patz, M.; Müller, M.; Mayr, H. J. Am. Chem. Soc. 1998, 120, 3629-3634.
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J. Am. Chem. Soc.
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Burfeindt, J.1
Patz, M.2
Müller, M.3
Mayr, H.4
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33
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0037023442
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Bear, T. J.; Shaw, J. T.; Woerpel, K. A. J. Org. Chem. 2002, 67, 2056-2064.
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J. Org. Chem.
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Bear, T.J.1
Shaw, J.T.2
Woerpel, K.A.3
-
34
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0242395100
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-
note
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With each Lewis acid, the counterion for the oxocarbenium ion is different, but the selectivity is independent of this counterion. In addition, because the selectivities are insensitive to the solvent, ion pairing is not evidently important.
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-
-
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35
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0242395101
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-
note
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The diastereoselectivity of this nucleophilic substitution is independent of the ratio of anomeric acetates, consistent with the intermediacy of oxocarbenium ions (details of these experiments are provided as Supporting Information).
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-
-
-
36
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0242562321
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-
note
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Additional details are provided as Supporting Information.
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-
-
-
37
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0242562320
-
-
While other conformations of the eight-membered ring may be relatively close in energy, it is the conformation of the five-membered ring that is important in controlling stereoselectivity. Oxocarbenium ion 21 and the product 22 are shown with the eight-membered ring in a boat-chair conformation, because the eight-membered rings of trans-fused eight-five ring systems adopt boat-chair forms: Umehara, M.; Hosomi, H.; Ohba, S. Acta Crystallogr., Sect. C 1999, 55, 1721-1725.
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(1999)
Acta Crystallogr., Sect. C
, vol.55
, pp. 1721-1725
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Umehara, M.1
Hosomi, H.2
Ohba, S.3
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38
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-
0002538534
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-
The dihedral angle between C3 and C4 within the five-membered ring of structure 25 is about 25° smaller than that for the chair conformation of cyclohexane. Consequently, the six-membered ring of 25 should be distorted from a chair conformation by a comparable angle. For a review of five-membered ring conformational analysis, see: Fuchs, B. Top. Stereochem 1978, 10, 1-94.
-
(1978)
Top. Stereochem.
, vol.10
, pp. 1-94
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Fuchs, B.1
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