A novel, short and efficient synthesis of divinyl ethers

Article abstract of DOI:10.1016/S0040-4039(03)01079-7

An efficient one-step synthesis of divinyl ethers from aldehydes and ketones using Wittig olefination is described.

Full text of DOI:10.1016/S0040-4039(03)01079-7

TETRAHEDRON
LETTERS
Pergamon
Tetrahedron Letters 44 (2003) 4913–4914
A novel, short and efficient synthesis of divinyl ethers
Mukund G. Kulkarni,* Aniruddha K. Doke, Saryu I. Davawala and Ajit V. Doke
Department of Chemistry, University of Pune, Pune 411007, India
Received 5 August 2002; revised 12 April 2003; accepted 25 April 2003
Abstract—An efficient one-step synthesis of divinyl ethers from aldehydes and ketones using Wittig olefination is described.
© 2003 Elsevier Science Ltd. All rights reserved.
The special structure of divinyl ether has been of inter-
est for many reasons. It displays rather unique
thermodynamic1 as well as spectroscopic2 properties. It
is an excellent substrate for investigating the photo-
chemical oxa di-p methane rearrangement.3 The parent
compound was used as an anaesthetic.4 The divinyl
ether structural motif is a part of a group of
compounds5 known as ‘oxylipins’. These serve as
important signal molecules for the expression of
defence gene against plant pathogens.6 The oxylipins
act as antimicrobial agents as well.7 In spite of such
diverse properties displayed by this simple structural
unit there is no simple and general method for the
synthesis of divinyl ethers, except for a few reports for
the synthesis of specific compounds involving dehydro-
halogenation of the corresponding b,b%-dihalo ethers at
elevated temperature,8 isomerisation of diallyl ethers
using palladium on carbon9 and using 5,5-disubstituted-
3-nitrosooxazolidones.10
with triphenylphosphine gave the Wittig salt 3a in good
yield. Reaction of the salt 3a with veratraldehyde
(Table 1, entry 1), using excess base, gave the corre-
sponding divinyl ether rather than the allyl vinyl ether.
This constituted a novel protocol for the synthesis of
divinyl ethers.
Reaction of various aldehydes and ketones with the salt
3a gave the respective divinyl ethers in good yields
(Table 1). A conjugated aldehyde also reacted with the
salt 3a as well to give the corresponding dienol vinyl
ether in good yield (Table 1, entry 7). Unlike the olefin
in allyl alcohol, the 1,1 disubstituted olefin in 2-phenyl
-2-propen-1-ol 1a is presumably sufficiently electron
rich so that hydrogen chloride adds across it under the
reaction conditions. As a result the dichloro compound
2a is formed. From the Wittig salt 3a, obtained from
the chloro compound 2a, the corresponding phospho-
rane is generated, in situ, on treatment with the base.
Recently, we have reported a novel protocol for the
synthesis of allyl vinyl ethers.11 This involves the prepa-
ration of allyl chloromethyl ether† which on treatment
with triphenylphosphine, gave the corresponding Wittig
salt. While attempting to extend this method to 2-
phenyl-2-propen-1-ol 1a, the dichloro compound 2a
was obtained when dry hydrogen chloride gas was
bubbled through a mixture of 1a and paraformaldehyde
(Scheme 1). Apparently, concomitant addition of
hydrogen chloride had taken place across the 1,1-disub-
stituted olefin in 1a along with the chloromethylation of
the alcohol. Reaction of the dichloro compound 2a
* Corresponding author. Tel./fax: +91 020 5691728; e-mail:
mgkulkarni@chem.unipune.ernet.in
Scheme 1. Reagents and conditions: (i) (HCHO)n, dry HCl(g)
benzene, 5–10°C, stir, 6 h, (76%); (ii) PPh3, benzene, rt, stir,
20 h, (78%).
,
† Caution: Chloromethyl ethers are potent carcinogens and should be
handled with due precautions.
0040-4039/03/$ - see front matter © 2003 Elsevier Science Ltd. All rights reserved.
doi:10.1016/S0040-4039(03)01079-7

4914
M. G. Kulkarni et al. / Tetrahedron Letters 44 (2003) 4913–4914
Table 1. Wittig olefination of aldehydes and ketones
alcohols yields divinyl ethers via the pathway discussed
above.
In conclusion, the reaction sequence presented here
constitutes a general, simple, efficient and convenient
methodology for the synthesis of divinyl ethers.
General procedure for Wittig olefination: Potassium t-
butoxide (2.5 equiv.) in t-butanol was added dropwise
over 5 min to the stirred suspension of aldehyde or
ketone (1 equiv.) and Wittig salt (3a or 3b; 1.2 equiv.)
in dry THF at 0°C under nitrogen. The reaction was
further stirred for 25 min at 0°C. It was quenched using
ice-cold water and extracted with ether. The organic
layer was dried over anhydrous sodium sulphate and
concentrated to give the crude product. Purification on
a column of silica gel (100–200 mesh) using hexane:
ethyl acetate, (98:2) as eluent gave the corresponding
divinyl ether.
Acknowledgements
A.K.D. thanks CSIR, New Delhi for a fellowship.
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