Acetals, their preparation and their use

Chemistry of hydrocarbon compounds – Unsaturated compound synthesis – By addition of entire unsaturated molecules – e.g.,...

Reexamination Certificate

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C585S520000, C502S169000, C502S171000, C502S172000, C549S206000, C549S210000, C549S472000, C549S502000

Reexamination Certificate

active

06235956

ABSTRACT:

The present invention relates to acetals, to methods for preparing them and to their use.
Within the context of research into catalysts for oligmerizing ethylene to light alpha-olefins, the Applicant became interested in acetals which can form a complex with zirconium which have high catalytic activity for this particular oligomerization reaction.
The prior art describes two general methods for synthesizing ketone acetals. One method consists of reacting an ortho-ester with a ketone to produce the desired ketone acetal. The same acetals are obtained using a second type of reaction which consists of reacting an acetylene substituted with two moles of alcohol. Other methods for synthesizing acetals can be added to those two principal methods: one method which consists of reacting an aldehyde or a ketone with one—or more—alcohols, and a method, known as transacetalization; using an acetal and an alcohol. Other indirect methods for synthesizing acetals are also known, but are seldom used.
“Non cyclic” acetals can be synthesized using conventional prior art methods. The term “non cyclic acetal” as used in the present description means acetals with the formula below in which groups R1 and R2 do not form a cycle.
They can be synthesised using transacetalization. That synthesis thus necessitates displacing the equilibrium towards the desired acetal to obtain good yields and to separate the desired acetal from other products and excess reactants. The acetal can be separated from the other constituents of the mixture by distillation when the boiling points of the different constituents of the mixture allow it; also distillation of an alcohol-acetal azeotrope can be used if one exists. If no alcohol-acetal azeotrope exists, other means must be employed to isolate the desired acetal.
A study of the prior art reveals a number of documents on acetal synthesis.
Thus N. B. Lorette and W. L. Howard, in Organic Synthesis Coll. Vol. V, p. 5, describe a general method for synthesising acetals from acetone by transacetalization from 2,2-di(methoxy)propane and the alcohol corresponding to the desired acetal. In those syntheses, the acetals are such that groups R3 and R4 in the above general formula are identical The term “alcohol corresponding to the desired acetal” means an alcohol with formula R3OH (or R4OH since R3 and R4 are identical).
Fieser and Fieser, in “Reagents for Organic Synthesis”, Vol. 5, p. 360, describe a further method for synthesizing acetone acetals from 2-methoxypropene.
In the prior art documents, two indirect methods for synthesizing formol acetals have been retained. A first method by B. S. Bal and H. W. Pinnick in J. Org. Chem. Vol. 44, p. 3727-3728 (1979) describes producing formaldehyde acetals from the alcohol corresponding to the desired acetal dimethylsulphoxide and trimethylchlorosilane. In those syntheses, the acetals are such that groups R3 and R4 in the above general formula are identical.
A further method by B. C. Barot, H. W. Pinnick in J. Org. Chem. Vol. 46, p. 2981-2983 (1981). describes producing symmetrical formol acetals by interconversion of a disymmetrical acetal with elimination of the volatile symmetrical acetal.
The acetals of the present invention are acetone acetals and formol acetals which are represented by the following general formula:
where R1 and R2 are methyl groups and R3 and R4, which are identical, are 2,2-dimethylpropyl groups, or hexyl groups, or decyl groups, or dodecyl groups, or tetradecyl groups, or hexadecyl groups, or octadecyl groups or tetrahydrofurfuryl groups;
or where R1 and R2 are methyl groups and R3 and R4 are different and are a methyl group and an octadecyl group;
or where R1 and R2 are hydrogen atoms and R3 and R4 are identical and are hexyl groups or 2-ethylhexyl groups, or hexadecyl groups.
Straight chain alcohols in particular can be used, to obtain the following compounds in which R1 and R2 are methyl groups and R3 and R4 are two n-hexyl groups, or two n-decyl groups, or two n-dodecyl groups, or two n-tetradecyl groups, or two n-hexadecyl groups, or two n-octadecyl groups or a methyl group and an n-octadecyl group; or in which R1 and R2 are hydrogen atoms and R3 and R4 are two n-hexyl groups, or two n-hexadecyl groups.
A first series of acetone acetals was synthesized by transacetalization of 2,2-di(methoxy)propane using the general procedure described by N. B. Lorette and W. L. Howard; a further disymmetrical acetal was then synthesized using the method described by Fieser and Fieser.
Further, formol acetals were synthesized using the method described by B. S. Bal and H. W. Pinnick.
The acetals of the present invention were synthesized, separated and purified using conventional purification and separation processes the selection of which depends on the specifications of each acetal. These products were characterized by their nuclear magnetic resonance spectrum using di-deuterated dichloromethane (NMR (CD
2
Cl
2
)) and in some cases by infra red (IR) spectroscopy. ,
These acetals were then complexed with a zirconium compound and the activity of these complexes for oligomerizing ethylene to alpha olefins was measured. This zirconium compound may be a zirconium halide and more particularly a zirconium tetrahalide such as zirconium tetrachloride ZrCl
4
, zirconium tetraiodide ZrI
4
, zirconium tetrabromide ZrBr
4
, or zirconium tetrafluoride ZrF
4
. This zirconium compound can also be a derivative with formula ZrR′
4
where R′ is an alkoxy group with formula R″O, or an amido group with formula R″
2
N or a carboxylate group with formula R″COO; R″ is thus a hydrocarbyl group or an alkyl group preferably containing about 1 to 30 carbon atoms. These alkoxide compounds are, for example, zirconium tetrapropylate with formula Zr(OC
3
H
7
)
4
, zirconium tetrabutylate with formula Zr(OC
4
H
9
)
4
; an example of the carboxylate compounds is tetra-2-ethyl-2-hexanate Zr(OCOC
7
H
15
)
4
.
The zirconium compound can also be an oxycarboxylate such as dizirconium-oxo-hexaethyl-2-hexanoate with formula [Zr(OCOC
7
H
15
)
3
]
2
O.
The present invention also relates to a process more particularly for synthesizing certain acetals be reacting a non cyclic carbonyl compound such as an aldehyde or a ketone with general formula R′1R′2C═O where R′1 and R′2, which may be identical or different, are hydrogen or aryl groups or linear or branched alkyl groups containing 1 to 20 carbon atoms, limits included, with at least one alcohol with general formula R′OH where R′ is a linear or branched hydrocarbon group containing 1 to 20 carbon atoms, limits included.
This particular aspect of the present invention relates to a process for synthesizing acetals from at least one alcohol R′OH in which R′ is a linear or branched alkyl group containing 1 to 20 carbon atoms, limits included, preferably 4 to 16 carbon atoms, limits included. More particularly, the present invention provides a process for synthesizing acetals from at least one alcohol with formula R′OH where R′ is a branched alkyl group, in particular an alkyl group containing a branch in the 2 position, such as 2-ethylhexyl.
The prior art describes two general methods for synthesizing ketone acetals. One method consists of reacting an ortho-ester with a ketone to produce the desired ketone acetal. The same acetals are obtained using a second type of reaction which consists of reacting an acetylene substituted with two moles of alcohol. Other methods for synthesizing acetals can be added to those two principal methods: one method which consists of reacting an aldehyde or a ketone with one—or more—alcohols, and a method, known as transacetalization, using an acetal and an alcohol. Other indirect methods for synthesizing acetals are also known, but are seldom used.
A study of the prior art reveals the following documents for acetal synthesis in particular.
These documents are: C. R. Hebd. Séances Acad. Sci., 257 <1963> p. 690-692, which describes the production of di-sec-octyloxy-2,2

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