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3,4-Dihydropyran

3,4-Dihydropyran (DHP) is a heterocyclic compound with the formula C5H8O. The six-membered C5O ring has the unsaturation adjacent to oxygen. The isomeric 3,6-dihydropyran has a methylene separating the double bond and oxygen. DHP is used for protecting group for alcohols. It is a colorless liquid.[1]

Preparation

Dihydropyran is prepared by the dehydration of tetrahydrofurfuryl alcohol over alumina at 300–400 °C.[2] THFA is itself prepared from tetrahydro-2-furoic acid.

Reactions

In organic synthesis, the 2-tetrahydropyranyl (THP) group is used as a protecting group for alcohols.[3][4] Reaction of the alcohol with DHP forms a THP ether, protecting the alcohol from a variety of reactions. The alcohol can later be restored by acidic hydrolysis, concomitant with formation of 5-hydroxypentanal.[5]

Protection of an alcohol as THP ether followed by its deprotection. Both steps require acid catalysts.

See also

References

  1. ^ Paul Ch. Kierkus (2001). "3,4-Dihydro-2H-pyran". EEROS. doi:10.1002/047084289X.rd230. ISBN 0471936235.
  2. ^ R. L. Sawyer and D. W. Andrus (1955). "2,3-Dihydropyran". Organic Syntheses; Collected Volumes, vol. 3, p. 276.
  3. ^ R. A. Earl L. B. Townsend (1990). "Methyl 4-Hydroxy-2-butynoate". Organic Syntheses; Collected Volumes, vol. 7, p. 334.
  4. ^ Arthur F. Kluge (1990). "Diethyl [(2-Tetrahydropyranyloxy)methyl]phosphonate". Organic Syntheses; Collected Volumes, vol. 7, p. 160.
  5. ^ Wuts, Peter G. M.; Greene, Theodora W. (2006). "Protection for the Hydroxyl Group, Including 1,2- and 1,3-Diols". Greene's Protective Groups in Organic Synthesis (4th ed.). pp. 16–366. doi:10.1002/9780470053485.ch2. ISBN 9780470053485.