Organic compounds -- part of the class 532-570 series – Organic compounds – Heavy metal containing
Reexamination Certificate
2000-04-07
2001-05-29
Nazario-Gonzalez, Porfirio (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Heavy metal containing
C502S080000, C502S084000
Reexamination Certificate
active
06239302
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an improved process for the preparation of acylferrocenes from ferrocenes using acid anhydrides as acylating agents and montmorillonite clays as catalysts.
2. Summary of the Related Art
Acylferrocenes are important intermediates for the production of varied functional materials such as functional polymers, surfactants, charge transfer complexes, ion sensors, masking agents, coupling agents, chiral catalysts, combustion catalysts for propellants, and the like. Acylferrocenes are also employed as a medicament for the treatment of sideropenia symptoms and sideropenic anemia (anemia caused by repeated bloodletting).
Friedel-Crafts acylation of ferrocene with acyl halides leads to the formation of acylferrocenes. Ferrocene is 10
6
times more reactive than benzene in acylation. They are generally prepared by reacting ferrocene with acetic anhydride/acyl chlorides in the presence of a Lewis acid such as aluminium chloride or polyphosphoric acid. It has been found that both acylferrocenes and diacylferrocenes can be prepared in satisfactory yields by varying the ratios of ferrocene and/or acid chloride, and by altering the mode of addition as well. Monoacylferrocenes are prepared by the drop-wise addition of the acid chloride-aluminium chloride complex to the ferrocene solution, using equimolar amounts of acid chloride, catalyst and ferrocene. The diacylferrocenes are prepared by adding ferrocene solution to the complex using a molar ratio of >2:1 of both the acid chloride and aluminium chloride to ferrocene.
Rosenblum and Woodward,
J. Am. Chem. Soc
., 80 5443, (1958) discloses the preparation of acylferrocenes by the reaction of ferrocene with acetyl chloride in the presence of stoichiometric quantities of aluminum chloride. “Vogels Textbook of Practical Organic Chemistry”, 5
th
Edition, 1014 (1989) teaches the preparation of acylferrocene by the reaction of ferrocene with acetic anhydride in the presence of 85% phosphoric acid.
Furthermore, British Patent Nos. BP 869504 and BP 819108 disclose the reaction of ferrocene with an appropriate acid chloride or anhydride under Friedel-Crafts conditions in the presence of Lewis acids such as aluminium chloride, boron trifluoride, hydrogen fluoride or polyphosphoric acid in solvents such as carbon disulfide, ethers, nitromethane or ethylene chloride. The drawbacks in these processes are that when aluminium chloride is used, diacyl compounds are usually obtained, whereas in the presence of hydrogen fluoride or polyphosphoric acid, monoacyl compounds are produced. Other drawbacks are the use of stoichiometric quantities of hazardous aluminium chloride or phosphoric acid and tedious work-up procedures.
It is thus necessary to find a novel process for making acylferrocenes that eliminates the use of the corrosive Lewis acids such as aluminum chloride. It is further desirable to find such a process that is more economical and more selective towards a particular product.
SUMMARY OF THE INVENTION
The present invention provides an improved process for the preparation of acylferrocenes from ferrocenes using acid anhydrides as acylating agents and montinorillonite clays as catalysts. More particularly, the present invention eliminates the need of employing corrosive and toxic acyl chlorides and Lewis acids (e.g. aluminium chloride, polyphosphoric alcid, boron trifluoride and hydrogen fluoride) by utilizing an eco-friendly process for the preparation of acylferrocenes from ferrocenes using acid anhydrides as acylating agents and montinorillonite clays as catalysts. The process of the present invention totally eliminates the formation, and thus the need to dispose of, salts formed in traditional Friedel-Crafts acylations.
It is therefore an object of the invention to provide a process for the preparation of acylferrocenes that is highly selective and substantially quantitative.
It is further an object of the invention to provide a process for the preparation of acylferrocenes that has a shorter duration as well as a simple work-up procedure.
It is another object of the invention to provide a process for the preparation of acylferrocenes in which economical and safe clays are used as catalysts in place of a Lewis acid. The present process envisages no disposal problem as the catalyst can be used for several cycles.
The invention offers excellent yields, greater selectivity towards monoacyl ferrocenes, and almost negligible effluents. The invention thus offers advantages over the prior art processes utilizing hazardous Lewis acids as catalysts. Therefore, the process described in this invention is technically feasible, economically viable and environmentally friendly.
DETAILED DESCRIPTION OF THE INVENTION
The invention relates to a process for the preparation of acylferrocenes employing commercially available montmorillonite and various metal ion exchanged acid catalysts for effecting acylation. The invention relates to the use of commercially available K10 montmorillonite and various metal ion exchanged K10 montmorillonites as solid acid catalysts for effecting acylation of ferrocenes with acid anhydrides as acylating agents. The invention offers excellent yields, greater selectivity towards monoacyl ferrocenes, and almost negligible effluents.
Accordingly, an embodiment of the present invention provides for a process for the preparation of acylferrocenes comprising reacting a ferrocene with an acid anhydride acylating agent in the presence of a montmorillonite or metal ion exchanged K10 montmorillonites clay catalyst in a solvent at a temperature in the range of about 60 to 165 deg celcius for a period of 3 to 8 hrs and recovering the acylferrocenes by conventional methods.
By “ferrocene” in the present invention is meant dicyclopentadienyliron as depicted by formula I:
By “acid anhydride” in the present invention is meant a compound of the formula (RCO)
2
O wherein R is lower alkyl or each R is connected to the other R such that, together with the carbonyl group to which each R attached, a carbocyclic ring is formed. In a preferred embodiment, the acylating agent is selected from the group of acid anhydrides having from 2 to 7 carbon atoms. Examples of preferred acid anhydrides for purposes of the present invention include, but are not limited to, acetic anhydride, propionic anhydride, butyric anhydride, valeric anhydride, hexanoic anhydride and heptanoic anhydride.
By “lower alkyl” in the present invention is meant straight or branched chain alkyl groups or cycloalkyl groups having 1-10 carbon atoms, such as, methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, pentyl, 2-pentyl, isopentyl, neopentyl, hexyl, 2-hexyl, 3-hexyl, and 3-methylpentyl, cyclopropyl, cyclopropylmethyl, and the like.
By “carbocyclic ring” is meant a saturated or aromatic hydrocarbon ring having a single ring (e.g., phenyl or cyclopentyl), multiple rings (e.g., biphenyl), or multiple condensed rings.
Suitable solvents for the present invention include, but are not limited to, (un)substituted hydrocarbon solvents such as, for example, chlorobenzene, acetonitrile or nitromethane. Another suitable solvent for the present invention is the acid anhydride itself. Acetic anhydride is a typical example where the acylating reagent can also act as the solvent. Preferred solvents of the present invention are chlorobenzene or acetic anhydride.
In yet another embodiment, the montmorillonitelmetal ion exchanged K10 montmorillonites clay catalyst is selected from Co
z+
, Z
z+
, Al
3+
, Ce
3+
, La
3+
, or Zr
4+
-montmorillonites. The amount of the catalyst used is from between 5 to 50% by weight with respect to the substrate charged. The catalyst is commercially available as, for example, K10 montmorillonite and various metal ion exchanged K10 montmorillonites as solid acid catalysts.
In acid treated montmorillonite, K10, the density of the Bronsted acidic sites increases because of increased number of broken edges resulting from the disruption of stacked laye
Choudary Boyapati Manoranjan
Kantam Mannepalli Lakshmi
Raghavan Kondapuram Vijaya
Reddy Konatham Saidi
Council of Scientific & Industrial Research
McDonnell Boehnen Hulbe & Berghoff
Nazario-Gonzalez Porfirio
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