[9017-40-7]  · (C7H7N)n  · Poly(4-vinylpyridine)  · (MW )n(105.15) (.HCl)

[29323-87-3]  · (C7H8ClN)n  · Poly(4-vinylpyridine hydrochloride)  · (MW )n(141.60)

(pyridine functional group in easily regeneratable solid form;1 acid scavenger;2 basic catalyst for Knoevenagel reactions;2 acid salts are mild acid catalysts3)

Alternate Names: P(4-VP); Reillex™.

Physical Data: Reillex 402: d 0.45 g cm-3. Reillex 425: d 0.29 g cm-3.

Solubility: insol all solvents; polymer swells when added to aqueous and nonaqueous solvents.

Form Supplied in: Reillex 402: 60 mesh, off-white granular powder. Reillex 425: 18-50 mesh, off-white beads. Drying: water may be removed from the polymer with toluene or other solvents that form water azeotropes.

Analysis of Reagent Purity: aqueous titration with acid; Reillex 402 has 8.8 mequiv/g H+ capacity and Reillex 425 has 5.5 mequiv/g H+ capacity.

Handling, Storage, and Precautions: extremely stable polymer best stored in tightly closed containers; after use the free base form of the polymer can be regenerated for further use by treatment with aqueous NaOH.

Acid Scavenger and Basic Catalyst.

Poly(4-vinylpyridine) is a polymeric reagent that replaces liquid Pyridine as acid acceptor in aqueous and nonaqueous media for reactions that produce acids as a byproduct.2 Hydrogen Chloride generated during esterification using acyl halides (eq 1),4 from silylation of a primary alcohol with diphenyl-t-butylchlorosilane (DPBSiCl) (eq 2),5 and mixed acid anhydride preparation from acyl halides and acids were trapped on the polymer (eq 3).6 Since the polymer is a solid, filtering it from the reaction mixture simplifies workup. After recovery, the polymer can be regenerated and used in further reactions.

In a recent method for the synthesis of azulenes, P(4-VP) was uniquely effective as an Tetrafluoroboric Acid scavenger that does not react with the tropylium tetrafluoroborate reagent or the carbocationic intermediates involved in the [3 + 2] annulation (eq 4).7 In the absence of this scavenger, protodesilylation of the allenylsilane starting material is observed.

In the synthesis of hydroxylamines, the polymer has also been used to trap benzoic acid in the oxidation of secondary amines with Dibenzoyl Peroxide (eq 5).8

Poly(4-vinylpyridine) also functions as a basic catalyst in Knoevenagel reactions (eq 6).2

Mild Acid Catalyst.

The hydrochloride salt of poly(4-vinylpyridine) is a polymeric reagent that acts as a mild acid catalyst in the preparation of acetals and carboxylic acid esters (eq 7)3 and in the preparation of tetrahydropyranyl derivatives of alcohols and phenols (eq 8).9

1. (a) Goe, G. L.; Marston, C. R.; Scriven, E. F. V.; Sowers, E. E. In Catalysis of Organic Reactions; Blackburn, D. W., Ed.; Dekker: New York, 1990; pp 275-286. (b) Fréchet, J. M. J.; de Meftahi, M. V. Br. Polym. J. 1984, 16, 193.
2. Getman, D.; Hagerty, D.; Wilson, G.; Wood, W. F. J. Chem. Educ. 1984, 61, 550.
3. Yoshida, J.; Hashimoto, J.; Kawabata, N. BCJ 1981, 54, 309.
4. Wood, W. F.; Fesler, M. J. Chem. Educ. 1986, 63, 92.
5. Cardillo, G.; Orena, M.; Sandri, S.; Tomasini, C. CI(L) 1983, 643.
6. Fife, W. K.; Zhang, Z.-D. TL 1986, 27, 4933.
7. Becker, D. A.; Danheiser, R. L. JACS 1989, 111, 389.
8. Biloski, A. J.; Ganem, B. S 1983, 537.
9. Johnston, R. D.; Marston, C. R.; Krieger, P. E.; Goe, G. L. S 1988, 393.

William F. Wood

Humboldt State University, Arcata, CA, USA

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