Preparation of cis—olefins

Details Preparation of cis—olefins Preparation of cis—olefins

1993-03-04

2001-12-25

Wood, Elizabeth D. (Department: 1755)

Chemistry of hydrocarbon compounds

Adding hydrogen to unsaturated bond of hydrocarbon, i.e.,...

Partial

C585S266000, C585S271000, C585S275000, C585S277000, C568S780000, C568S876000, C568S828000, C568S903000, C568S857000, C568S880000, C568S881000, C560S001000, C562S405000, C562S463000, C562S512000

Reexamination Certificate

active

06333441

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to the preparation of cis-olefins, and more particularly, a method for preparing cis-olefins through formic acid reduction of alkynes in the presence of palladium catalysts.
BACKGROUND OF THE INVENTION
Cis-olefins are useful intermediates for the synthesis of many fine chemicals, especially for the synthesis of bioactive materials having a double bond cis-conformed in their structural formula.
In the prior art, cis-olefins were prepared by the hydrogen reduction of alkynes using Lindlar catalysts. Also known in the art are silicon hydride reduction using palladium catalysts (Barley M. Trost, Tetrahedron Letters, Vol. 30, No. 35 pp. 4657, 1989).
These method have several drawbacks. The hydrogen reduction method using Lindlar catalysts is difficult to obtain cis-olefins of high purity since trans-olefins and saturated compounds are by-produced in addition to the desired cis-olefins. The hydrogen reduction method has the danger of a fire. The silicon hydride reduction method must use expensive silicon hydrides and is generally low in cis-olefin selectivity so that trans-olefins can be a major product.
In Tetrahedron, Vol. 44, pp. 481, 1988, A. Arcadi et al discloses formic acid reduction in which aryl iodides are reacted with alkyl 4-hydroxy-2-alkynoates and in the presence of formic acid, tri-n-butylamine and a palladium (II) catalyst.
However, the above formic acid reduction method only provides cyclic product as shown below. No cis-olefins which are pure hydrogenated products are available.
There is a need to have a simple method capable of selectively producing cis-olefins in high yields.
SUMMARY OF THE INVENTION
Therefore, an object of the present invention is to provide a method for selectively preparing cis-olefins without substantial formation of trans-olefins and saturated compounds.
The present invention is addressed to a method for preparing a cis-olefin of the following general formula (2):
wherein R
1
and R
2
are independently selected from the group consisting of a hydrogen atom, ester group, substituted silyl group, carboxyl group, cyano group, substituted or unsubstituted aliphatic hydrocarbon group having 1 to 20 carbon atoms, and substituted or unsubstituted phenyl group. The method is characterized by reducing an alkyne of the following general formula (1):
R
1
—C≡C—R
2
  (1)
wherein R
1
and R
2
are as defined above with formic acid in the presence of a palladium catalyst.
DETAILED DESCRIPTION OF THE INVENTION
The method of the invention starts with an alkyne of formula (1).
R
1
—C≡C—R
2
  (1)
In formula (1), R
1
and R
2
, which may be identical or different, are independently selected from the group consisting of (a) a hydrogen atom, (b) an ester group, (c) a substituted silyl group, (d) a carboxyl group, (e) a cyano group, (f) a substituted or unsubstituted aliphatic hydrocarbon group having 1 to 20 carbon atoms, and (g) a substituted or unsubstituted phenyl group. Examples of the group represented by R
1
and R
2
are given below.
Examples of (b) ester group include substituted or unsubstituted alkoxycarbonyl groups having 1 to 10 carbon atoms and substituted or unsubstituted phenoxycarbonyl groups. The substituted or unsubstituted alkoxycarbonyl groups having 1 to 10 carbon atoms include methoxycarbonyl, ethoxycarbonyl, n-propoxycarbonyl, i-propoxycarbonyl, n-butoxycarbonyl, sec-butoxycarbonyl, t-butoxycarbonyl, pentoxycarbonyl, hexoxycarbonyl, heptoxycarbonyl, octoxycarbonyl, nonanoxycarbonyl, decisoxycarbonyl, methoxymethoxycarbonyl, methylthiomethoxycarbonyl, tetrahydropyranoxycarbonyl, tetrahydrofuranotoxycarbonyl, benzyloxymethoxycarbonyl, phenasiloxycarbonyl, o-methylphenoxymethoxycarbonyl, m-methylphenoxymethoxycarbonyl, p-methylphenoxymethoxycarbonyl, o-bromophenasiloxycarbonyl, m-bromophenasiloxycarbonyl, p-bromophenasiloxycarbonyl, bezyloxycarbonyl, o-methylphenasiloxycarbonyl, m-methylphenasiloxycarbonyl, p-methylphenasiloxycarbonyl, 2,2,2-trichloroethoxycarbonyl, 2-chloroethoxycarbonyl, 2-methylthioethoxycarbonyl, cyclopentyloxycarbonyl, cyclohexyloxycarbonyl, allyloxycarbonyl groups, etc. The substituted or unsubstituted phenoxycarbonyl groups include biphenoxycarbonyl, 4-(4-fluorophenyl)phenoxycarbonyl, 4-(4-chlorophenyl)phenoxycarbonyl, 4-(4-bromophenyl)phenoxycarbonyl, 4-(4-iodophenyl)phenoxycarbonyl groups, etc.
Examples of (c) substituted silyl group include trimethylsilyl, i-propyldimethylsilyl, t-butyldimethylsilyl groups, etc.
Examples of (f) unsubstituted aliphatic hydrocarbon group having 1 to 20 carbon atoms include methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, sec-butyl, t-butyl, n-amyl, i-amyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, hexadecyl, octadecyl, eicosyl groups, etc.
The substituents on (f) aliphatic hydrocarbon groups and (g) phenyl group include hydroxyl, protected hydroxyl, halogen, formyl, ester, carbonyl, amide, carboxyl, cyano, p-methylthio, phenyl, fluorophenyl, chlorophenyl, bromophenyl, and iodophenyl groups.
By the protected hydroxyl groups are meant those hydroxyl groups protected with substituted silyl groups such as trimethylsilyl and t-butyldimethylsilyl groups, alkoxyalkyl groups such as methoxymethyl and ethoxymethyl groups, acyl groups such as acetyl and benzoyl groups, trityl, tetrahydropyranyl, benzyl and p-chlorobenzyl groups.
The ester substituents include substituted or unsubstituted alkoxycarbonyl groups having 1 to 10 carbon atoms and substituted or unsubstituted phenoxycarbonyl groups as mentioned for (b).
The halogen substituents include fluorine, chlorine, bromine and iodine atoms.
The amide substituents include substituted or unsubstituted alkoxycarbonylamide groups having 1 to 10 carbon atoms and substituted or unsubstituted phenoxycaronylamide groups. The substituted or unsubstituted alkoxycarbonylamide groups having 1 to 10 carbon atoms include methoxycarbonylamino, ethoxycarbonylamino, n-propoxycarbonylamino, i-propoxycarbonylamino, n-butoxycarbonylamino, sec-butoxycarbonylamino, t-butoxycarbonylamino, pentoxycarbonylamino, hexoxycarbonylamino, heptoxycarbonylamino, octoxycarbonylamino, nonanoxycarbonylamino, decisoxycarbonylamino, methoxymethoxycarbonylamino, methylthiomethoxycarbonylamino, tetrahydropyranoxycarbonylamino, tetrahydrofuranotoxycarbonylamino, benzyloxymethoxycarbonylamino, phenasiloxycarbonylamino, o-methylphenoxymethoxycarbonylamino, m-methylphenoxymethoxycarbonylamino, p-methylphenoxymethoxycarbonylamino, o-bromophenasiloxycarbonylamino, m-bromophenasiloxycarbonylamino, p-bromophenasiloxycarbonylamino, benzyloxycarbonylamino, o-methylphenasiloxycarbonylamino, m-methylphenasiloxycarbonylamino, p-methylphenasiloxycarbonylamino, 2,2,2-trichloroethoxycarbonylamino, 2-chloroethoxycarbonylamino, 2-methylthioethoxycarbonylamino, cyclopentyloxycarbonylamino, cyclohexyloxycarbonylamino, allyloxycarbonylamino groups, etc. The amide moiety of the alkoxycarbonylamide and phenoxycarbonylamide groups may have a substituent which is selected from the above-mentioned substituents on the C1-C10 aliphatic hydrocarbon and phenyl groups and which may further have a substituent such as a hydroxyl, protected hydroxyl, halogen, formyl, ester, amide, carboxyl, cyano, p-methylthio, phenyl, fluorophenyl, chlorophenyl, bromophenyl, and iodophenyl group.
Illustrative, non-limiting examples of the alkyne of formula (1) include 1-decyne, 1-hydroxy-4-heptyne, 1-hydroxy-2-octyne, 3-hydroxy-1-octyne, 3-hydroxy-4-decyne, 2-hydroxy-2-methyl-3-nonyne, 1-trimethylsilyl-1-heptyne, 1-t-butyldimethylsiloxy-2-octyne, 1-trimethylsilyl-3-hydroxy-1-octyne, 1-carboxy-3-hexyne, 1-carboxy-1-heptyne, 1-methoxycarbonyl-1-heptyne, 1-ethoxycarbonyl-4-heptyne, 1-allyloxycarbonyl-1-heptyne, 1-methoxycarbonyl-6-hydroxy-4-hexyne, 1-ethoxycarbonyl-3-hexyne, 3-oxy-4-decyne, 2-oxo-5-octyne, 1-benzyloxy-2-octyne, 1-tetrahydropyranoxy-2-octyne, 1-formyl-3-hexyne, 1-bromo-4-heptyne, 1-cyano-4-heptyne, phenylacetylene, 1-phenyl-1-butyne, and 1-phenylthio-4-heptyne.
According to the present invention, these alkynes are r

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