Process for the synthesis of organomagnesium compounds using...

Details Process for the synthesis of organomagnesium compounds using... Process for the synthesis of organomagnesium compounds using...

2001-03-15

2004-06-15

Vollano, Jean F. (Department: 1621)

Chemistry of carbon compounds

Miscellaneous organic carbon compounds

C-metal

Reexamination Certificate

active

06749778

ABSTRACT:

The present invention relates to an improved process for the preparation of organomagnesium compounds from organohalides and magnesium metal in the presence of transition metal catalysts and an activity-enhancing main group metal component.
PRIOR ART
Grignard compounds are usually prepared by reacting organic halides with magnesium in an ethereal solvent; in certain cases, they can also be prepared in hydrocarbons (Comprehensive Organometallic Chemistry II, Vol. 1, 1995, p. 58-63; Comprehensive Organometallic Chemistry I, Vol. 1, 1982, p. 155; Chem. Ber. 1990, 123, 1507 and 1517; Houben-Weyl, Methoden der organischen Chemie, 1973, 13/2a, 53-192).
However, there is a wide variety of organic halogen compounds, including, in particular, aromatic, vinylic and heterocyclic chloro compounds, with which the Grignard reaction proceeds hesitantly, with low yields, poorly or not at all. For increasing the reactivity of magnesium towards such halides, numerous methods are known which are based on physical (grinding, ultrasonication, metal vaporization) or chemical (entrainment method, Rieke method, dehydrogenation of magnesium hydride, reversible formation of magnesium anthracene) activation of magnesium (Active Metals—Preparation, Characterization, Applications, A. Fürstner (Ed.), Verlag Chemie, 1996). Further, a process for the preparation of Grignard compounds is known which is based on the physical and chemical activation of the magnesium metal employed (DE 27 55 300 A1, Schering A G). Thus, prior to performing the Grignard reaction, the magnesium metal is ground in the presence of organometallic aluminum, boron or zinc compounds in which the organo groups may also be partly substituted by halogens, hydrogen or alkoxy groups, and after the addition of organomagnesium compounds, it is converted to the corresponding Grignard compounds without further grinding with organyl halides. As catalysts for the Grignard reaction, anthracene or magnesium anthracene and their derivatives are known; however, they can be employed only in the case of allyl, propargyl and benzyl halides (Chem. Ber. 1990, 123, 1507). There are drawbacks in the mentioned methods in that they are either relatively tedious and expensive or subjected to limitations in application or effectiveness, or result in an increased consumption of magnesium (entrainment method: J. Org. Chem. 1959, 24, 504). Therefore, there is still a need for effective and economical methods for the preparation of Grignard compounds from the above mentioned inert organic halogen compounds which are not subject to the mentioned draw-backs, and with the proviso that conventional, commercially available magnesium grades can be used.
According to the Patent Application PCT/WO 98/02443 filed by the Studiengesellschaft Kohle, which corresponds to U.S. Ser. No. 09/214,369, filed Jan. 5, 1999, a process for the preparation of Grignard compounds is known which is characterized in that organic halides are reacted with magnesium metal in an ethereal solvent in the presence of catalysts consisting of inorganic Grignard reagents of transition metals having the general formula [M(MgX)
m
(MgX
2
)
n
]
2
, wherein M is a transition metal of Periodic Table groups 4-10, X is a halogen, m=1, 2, 3, n=0−1, and optionally anthracene or substituted anthracenes or their Mg adducts and/or magnesium halides as cocatalysts. Iron halides and manganese halides are considered the preferred catalyst components according to the mentioned process. A preferred mode of carrying out the process involves performing the reaction of organic chlorine compounds with magnesium powder in the presence of catalysts prepared from iron or manganese halides, 9,10-diphenylanthracene, magnesium halide and excess Mg powder in THF, monoglyme or diglyme.
According to the Patent Application PCT/EP 98/08056 filed by the Studiengesell-schaft Kohle mbH, which corresponds to U.S. Ser. No. 09/581,874, filed Jun. 19, 2000, transition metal compounds in which elements of groups 15 or 16 (preferably N or O) are bonded to the transition metal are also suitable catalysts. Particularly preferred are those transition metal catalysts which contain Fe, Mn, Co and Cu bound to alkoxy, aryloxy, amido and phthalocyanine groups.
DESCRIPTION OF THE INVENTION
Surprisingly, it has now been found that the catalytic activity of the transition metal catalysts in which one or more elements selected from groups 14, 15, 16 or 17 are bonded to a metal selected from the metals of groups 3, 4, 5, 6, 7, 8, 9, 10 or 11 can be significantly improved by the addition of a main group metal component (Angew. Chem. 2000, 112, No. 24, 4788-4790). For this purpose, compounds of main group metals of Periodic Table groups 1, 2 and 13 (especially Li, Na, Mg, Al or B) are used in which one or more elements of Periodic Table groups 14, 15, 16 or 17 (especially C, N, O or halogens) or hydrogen are bonded to the metal. The main group metal additional components according to the invention are preferably employed in the form of alkyl, aryl, alkoxy, aryloxy, alkylamido, arylamido, phthalocyanine, halogen and/or hydrogen compounds. Some of these additional components may also be formed in situ (such as RMgX, formed from RX, where R is an alkyl or aryl residue and X is a halogen atom, and Mg metal, being present in excess). The said alkyl, alkoxy or alkylamido compounds are preferably employed with a chain length of from C
1
to C
16
, whereas the aryl, aryloxy or arylamido compounds are preferably employed as phenyl compounds or substituted compounds of this kind, and the halogens are preferably employed in the form of chlorine, bromine or iodine.
The transition metal catalyst comprises a transition metal selected from Periodic Table groups 3, 4, 5, 6, 7, 8, 9, 10 or 11, and one or more elements selected from groups 14, 15, 16 or 17 bonded to the transition metal. The transition metal catalyst, for example, contains Fe, Mn, Co or Cu.
The additional main group metal component used according to the present process includes, for example, Grignard compounds (such as EtMgCl, phenyl-MgCl), diorganomagnesium compounds (such as diethylmagnesium), magnesium hydride, HMgCl, organomagnesium alcoholates (such as phenyl-MgOEt), magnesium phthalocyanine, lithium hydride, Li, Na, Al or B organyls (such as triethylaluminum, butyllithium, triphenylboron) as well as diorganoaluminum hydride and chloride (such as diisobutylaluminum hydride or diethylaluminum chloride).
The main group metal additional components of the present process (e.g. AlEt
3
and EtMgBr) alone do not cause catalysis of the Grignard reaction (Example 9, Comparative Examples); however, when used together with the transition metal compounds mentioned, enhanced catalytic effects are observed.
The catalyst components according to the invention reduce the transition metal compound into a form which is particularly active catalytically. Thus, they do not function as mere magnesium metal activation agents (such as the organoaluminum, organoboron or organozinc compounds in DE 27 55 300 A1, Schering A G), but they are chemical reactants in the preparation of particularly active transition metal catalysts (see Examples 1, 2, 9, and Comparative Examples), where they are consumed partially or completely. Thus, for example, ferrous chloride will react with the organomagnesium compound n-heptylmagnesium bromide with reduction of the iron and release of heptane and heptene to yield a particularly active catalyst.
Also, it was found that, in addition to the catalysts of transition metals described in PCT/WO 98/02443 and PCT/EP 98/08056, organometallic compounds of these elements, such as metallocenes, e.g. ferrocene, and substituted metallocenes can also be used as catalysts for Grignard synthesis.
The magnesium metal is employed in the form of commercially available powders, dusts, raspings, granules, chips or turnings (preferably as a powder). If necessary, the magnesium metal may be employed in an activated form or be continuously activated superficially, while the reaction is perfor

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