Org. Synth. 1954, 34, 29
DOI: 10.15227/orgsyn.034.0029
3,4-DIHYDRO-2-METHOXY-4-METHYL-2H-PYRAN
[2H-Pyran, 3,4-dihydro-2-methoxy-4-methyl-]
Submitted by Raymond I. Longley, Jr., William S. Emerson, and Albert J. Blardinelli
1.
Checked by T. L. Cairns and T. E. Young.
1. Procedure
In a high-pressure autoclave, arranged for agitation by shaking or rocking, are placed 286 g. (336 ml., 4.08 moles) of crotonaldehyde, 294 g. (5.06 moles) of methyl vinyl ether, and 1.1 g. of hydroquinone (Note 1) and (Note 2). The autoclave is heated to 200° (Note 3) and held there for 12 hours. The autoclave is cooled and vented, and the black product is distilled through a 1 by 60 cm. helix-packed column. The yield of 3,4-dihydro-2-methoxy-4-methyl-2H-pyran is 270–297 g. (52–57%), b.p. 42–50° /19 mm., n25D 1.4349–1.4374 (Note 4), (Note 5), and (Note 6).
2. Notes
1.
The
purer grade of crotonaldehyde supplied by the Eastman Kodak Company was used.
Methyl vinyl ether was obtained from the Matheson Chemical Company.
2.
The submitters condensed the
methyl vinyl ether in the aldehyde cooled to 0° and then charged this mixture to a precooled autoclave. The checkers cooled the autoclave containing the
crotonaldehyde to −70°, evacuated, and condensed the required amount of
methyl vinyl ether directly into the autoclave.
3.
The autoclave should be capable of withstanding a pressure of 3000 p.s.i. This provides a margin of safety, since at 220° the pressure is about 2600 p.s.i.
4.
Pure
3,4-dihydro-2-methoxy-4-methyl-2H-pyran boils at
135–138° /760 mm. and at
79–80° /100 mm. and has
n25D 1.4370.
5.
The submitters used approximately three times the quantities reported here and obtained yields of
82–83%.6.
Under comparable conditions the submitters found that the corresponding dihydropyran derivatives were similarly obtained by the condensation of
acrolein with
methyl vinyl ether in 80–81% yield, with
ethyl vinyl ether (77–85% yield), with
n-butyl vinyl ether (82% yield), with
ethyl isopropenyl ether (50% yield), and with
n-butyl cyclohexenyl ether (40% yield). Other α,β-unsaturated carbonyl compounds that have thus been condensed with
ethyl vinyl ether are
crotonaldehyde (87% yield),
methacrolein (40% yield),
α-ethyl-β-n-propylacrolein (54% yield),
cinnamaldehyde (60% yield),
β-furylacrolein (85% yield),
methyl vinyl ketone (50% yield),
benzalacetone (75% yield), and
benzalacetophenone (74% yield).
3. Discussion
3,4-Dihydro-2-methoxy-4-methyl-2H-pyran has been prepared only by the addition of
methyl vinyl ether to
crotonaldehyde.
2,3,4,5
This preparation is referenced from:
Appendix
Chemical Abstracts Nomenclature (Collective Index Number);
(Registry Number)
Acrolein (107-02-8)
hydroquinone (123-31-9)
Benzalacetophenone (94-41-7)
Benzalacetone (122-57-6)
cinnamaldehyde
crotonaldehyde (123-73-9)
methyl vinyl ketone (78-94-4)
3,4-Dihydro-2-methoxy-4-methyl-2H-pyran,
2H-Pyran, 3,4-dihydro-2-methoxy-4-methyl- (53608-95-0)
methyl vinyl ether (9003-09-2)
ethyl vinyl ether (109-92-2)
ethyl isopropenyl ether (926-66-9)
methacrolein (78-85-3)
β-furylacrolein (623-30-3)
n-butyl vinyl ether (111-34-2)
n-butyl cyclohexenyl ether
α-ethyl-β-n-propylacrolein
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