3,4-Dihydro-2H-pyran NEW

Appearance and properties: colorless liquid

Density: 0.922 g/mL at 25 °C(lit.)

Boiling point: 86 °C(lit.)

Melting point: −70 °C(lit.)

Flash point: 4 °F

Refractive index: n20/D 1.440(lit.)

Water solubility: 20 g/L (20 ºC)

Stability: Stable under normal temperatures and pressures.

Storage condition: Flammables area

Steam density: 2.9 (vs air)

Vapor pressure: 74.4mmHg at 25°C

Production method

It is obtained by dehydration and ring enlargement of tetrahydrofurfuryl alcohol.

Use

Tetrahydropyran, pentadiol, glutaric acid, valerolactone, pentadiene and resin products can be prepared by polymerization, hydrogenation, oxidation and other reactions. It can also be used as pharmaceutical intermediates. Solvents, intermediates of organic synthesis. It is widely used for the protection of hydroxyl groups, generally does not react with nucleophiles and organometallic reagents, is resistant to strong alkali, and is easy to change under low pH value or Lewis acid conditions. Tetrahydropyranization of alcohols Tetrahydropyran (THP) is a useful tool for the protection of alcohols in organic synthesis. The reaction of chiral alcohols with dihydropyranes introduces another asymmetric center, thus giving a diastereoscopic mixture (formula 1). This brings some difficulties to purification and spectral analysis, but does not prevent its successful application. Under very mild reaction conditions (0 oC, 1 h, 89%~100%), tetrahydropyranylation of alcohols can occur with (trimethylsilyl) sulfate, and no rearrangement will occur even with allyl tertiary alcohols. In the presence of MEM ether, MOM ether, and 1, 3-dioxyclopentane, organotin phosphate condensation is very effective for the selective splitting of TEM ethers, and the catalyst can be reused. The selective cleavage of THP ethers of primary, secondary and tertiary alcohols occurs in the presence of tert-butyldimethylsilyl, acetyl, methylsulfonyl and methoxymethyl ether, as well as in the presence of Me2Sn(SMe)2-BF3·Et2O. Tetrahydropyranization of mercaptan tetrahydropyran derivatives of mercaptan can be used in shielding reactions of functional groups (Formula 2). Compared with O-tetrahydropyranopyran ether, S-tetrahydropyranopyran ether can also exist stably at 4mol/L HCl-MeOH. Deprotection with silver nitrate or hydrogen bromo-trifluoroacetic acid is easily performed and has a high yield. Oxidation reactions can occur with iodine or cyanide sulfide or disulfide. In the presence of a catalytic amount of p-toluene sulfonic acid, purine reacts with dihydropyran to form a 9-(2-tetrahydropyran) derivative (Formula 3). Ring-opening reaction of dihydropyran Dihydropyran treated with n-amyl sodium or n-butyllithium generates trans-4-hydroxy-1-ol (formula 4). Groups protected by THP are widely used in organic synthesis. The structure of the cis-Ch =CHCH2OH can be introduced using a Gilman cuprate reagent with a chain-end protective ether (equation 5). The azine compound of dihydropyran and BrCH2C(NOH)CO2Et can be used in the synthesis of aminotriesters (Formula 6). A simple, effective and highly chemically selective method of tetrahydropyranylation of alcohols and phenolic compounds is carried out at room temperature under the action of polystyrene supported by AlCl3 in catalytic quantities. This method is highly selective for the monoprotection of symmetric diols (equation 7).

Preparation of Dihydropyran:
Dihydropyran is prepared by the dehydration of tetrahydrofurfuryl alcohol over alumina at 300-400 °C.


Safety Information of Dihydropyran:
The Dihydropyran is irritating to eyes, respiratory system and skin. It is highly flammable,so keep away from sources of ignition. it may form explosive peroxides. Keep container tightly closed. And keep container in a well-ventilated place.Take precautionary measures against static discharges. When you use it ,wear suitable protective clothing, suitable gloves and eye/face protection. In case of contact with eyes, rinse immediately with plenty of water and seek medical advice.