Field of the Invention

This invention relates to methods for preparing octane-boosting additives for use in a fuel for a spark-ignition internal combustion engine. In particular, the invention relates to methods for preparing octane-boosting fuel additives that are derivatives of

benzo[l,4]oxazines and l,5-benzoxazepines. The invention further relates to methods for preparing fuels for a spark-ignition internal combustion engine comprising the fuel additives.

Background of the Invention

Spark-ignition internal combustion engines are widely used for power, both domestically and in industry. For instance, spark-ignition internal combustion engines are commonly used to power vehicles, such as passenger cars, in the automotive industry.

Fuels for a spark-ignition internal combustion engine (generally gasoline fuels) typically contain a number of additives to improve the properties of the fuel.

One class of fuel additives is octane improving additives. These additives increase the octane number of the fuel which is desirable for combatting problems associated with pre-ignition, such as knocking. Additisation of a fuel with an octane improver may be carried out by refineries or other suppliers, e.g. fuel terminals or bulk fuel blenders, so that the fuel meets applicable fuel specifications when the base fuel octane number is otherwise too low.

Organometallic compounds, comprising e.g. iron, lead or manganese, are well- known octane improvers, with tetraethyl lead (TEL) having been extensively used as a highly effective octane improver. However, TEL and other organometallic compounds are generally now only used in fuels in small amounts, if at all, as they can be toxic, damaging to the engine and damaging to the environment.

Octane improvers which are not based on metals include oxygenates (e.g. ethers and alcohols) and aromatic amines. However, these additives also suffer from various drawbacks. For instance, N-methyl aniline (NMA), an aromatic amine, must be used at a relatively high treat rate (1.5 to 2 % weight additive / weight base fuel) to have a significant effect on the octane number of the fuel. NMA can also be toxic. Oxygenates give a reduction in energy density in the fuel and, as with NMA, have to be added at high treat rates, potentially causing compatibility problems with fuel storage, fuel lines, seals and other engine components.

Recently, a new class of octane-boosting additive has been discovered. These octane-boosting additives are derivatives of benzo[l,4]oxazines and l,5~benzoxazepines, and show great promise due to their non-metallic nature, their low oxygenate content, and their efficacy at low treat rates (see WO 2017/137518). Preferred octane-boosting additives in this class are substituted on one or more of the carbons forming part of the aromatic or heterocyclic ring.

Synthesis routes currently reported in the literature provide various descriptions of how benzoxazines could be prepared on a relatively small scale (hundreds of mg to up to 100 kg scale). For example, US 2008/064871 - which relates to compounds for the treatment or prophylaxis of diseases relating to uric acid, such as gout - discloses the preparation of benzoxazine-derived compounds.

However, such synthesis methods are not viable for preparing the new class of octane-boosting additives on an industrial scale, e.g. from 50 to up to 20,000 tonnes per year, due to the high cost of specialised raw materials, e.g. methylaminophenols, and reagents, e.g. lithium aluminium hydride and dibromoethane, which are required in stoichiometric amounts.

Accordingly, there is a need for methods for synthesising the new class of octane- boosting additives that may be implemented on a large scale and which mitigate at least some of the problems highlighted above, e.g. by avoiding the use of costly aminophenol starting materials.

Summary of the Invention

The present invention provides a method for preparing a fuel additive d having the formula:

where: Ri is hydrogen; R ₂ , R ₃ , 4, R ₅ , Rn and RJ ₂ are each independently selected from hydrogen, alkyl, alkoxy, alkoxy-alkyl, secondary amine and tertiary amine groups;

R ₆ , R ₇ , R ₈ and R ₉ are each independently selected from hydrogen, alkyl, alkoxy, alkoxy-alkyl, secondary amine and tertiary amine groups;

X is selected from -O- or -NR10-, where Ri ₀ is selected from hydrogen and alkyl groups; and

n is 0 or 1.

The method comprises carrying out the following reaction:

where: each Y is independently selected from halides.

Also provided is a fuel additive d which is obtainable by a method of the present invention.

The present invention further provides a process for preparing a fuel for a spark- ignition internal combustion engine, said process comprising:

preparing a fuel additive d using a method of the present invention; and

blending the fuel additive with a base fuel.

A fuel for a spark-ignition internal combustion engine is also provided. The fuel comprises a fuel additive d of the present invention and a base fuel.

Detailed Description of the Invention

Preparation methods

The present invention provides a method for preparing a fuel additive d. According to this method, the fuel additive d is prepared by carrying out the following reaction:

Starting material a comprises the group Y. Each Y is independently selected from halides, preferably from Br, Cl and I, and more preferably from Br and Cl.

The reaction is preferably carried out in the presence of a metal catalyst. Preferred metal catalysts are selected from palladium catalysts ( e.g . organometallic palladium catalysts, such as tris(dibenzylideneacetone)dipalladium(0) (also known as Pd ₂ (dba) ₃ ) and [l,l'-bis(di-fer/-butylphosphino)ferrocene]dichloropalladium (II) (also known as

PdCl2(dtbpf)) and copper catalysts (e.g. elemental copper, copper (I) halides (such as copper (I) bromide or copper (I) iodide) and copper (I) oxide), and more preferably from copper catalysts.

In some embodiments, the reaction is carried out in the presence of a combination of catalysts, e.g. a combination of a palladium catalyst and a copper catalyst, such as a combination of those catalysts described above.

The catalyst may be used in combination with an organic ligand preferably selected from organophosphorus ligands (e.g. selected from 2-dicyclohexylphosphino-2',4',6'- triisopropylbiphenyl (also known as XPhos), 2-(dicyclohexylphosphino)3,6-dimethoxy- 2',4',6'-triisopropyl-l,T-biphenyl (also known as BrettPhos), 2-di-fer/-butylphosphino- 2',4',6'-triisopropylbiphenyl (also known as /BuXPhos), 2-dicyclohexylphosphino-2',6'- diisopropoxybiphenyl (also known as RuPhos)), an alkanolamine (e.g. ethanolamine), aniline derived ligands (e.g. di(methylamino)benzenes) and ligands derived from amino acids (e.g. proline, hydroxyproline and N,N-dimethyl glycine).

For instance, organophosphorus ligands, particularly XPhos, are may be used with palladium catalysts, in particular Pd ₂ (dba) ₃ . Alkanolamines (e.g. ethanolamine), aniline derived ligands (e.g. di(methylamino)benzenes) and ligands derived from amino acids (e.g. proline, hydroxyproline and N,N-dimethyl glycine) may be used with copper catalysts, such as copper halides. Where a ligand is used, in may be used in an amount of from 1 to 10 molar equivalents, preferably from 2 to 8 molar equivalents, and more preferably from 3 to 6 molar equivalents as compared to the catalyst.

Suitable solvents for conducting the reaction include toluene, tert- amyl alcohol, dimethylformamide, ethanolamine, tetrahydrofuran and dioxane.

In some embodiments, the method of the present invention comprises a step of combining the catalyst, the organic ligand and the solvent and heating the mixture, e.g. to a temperature of greater than 30 °C, preferably greater than 40 °C, and more preferably greater than 50 °C, before combining the mixture with starting material a. Preferably, the mixture is allowed to cool to room temperature (e.g. to a temperature of from 15 to 25 °C) before it is combined with starting material a.

The catalyst may be used in an amount of from 0.01 to 1 molar equivalents, preferably from 0.02 to 0.5 molar equivalents, and more preferably from 0.03 to 0.3 molar equivalents as compared to starting material a.

The reaction is preferably earned out in the presence of a base, preferably an inorganic base, and more preferably an alkali metal base. For instance, the base may be selected from alkali metal carbonates (e.g. sodium carbonate, potassium carbonate or caesium carbonate), alkali metal alkoxides (e.g. alkali metal /er/-butoxides such as sodium /e/Y-butoxide or potassium /e/7-butoxide), alkali metal hydrides (e.g. sodium hydride or potassium hydride), alkali metal organosilicon compounds (e.g. lithium

bis(trimethylsilyl)amide) and alkali metal phosphates (e.g. trialkali metal phosphates such as tripotassium phosphate).

The base may be used in an amount of from 0.5 to 2 molar equivalents, preferably from 0.7 to 1.5 molar equivalents, and more preferably from 0.8 to 1.25 molar equivalents as compared to starting material a.

Reagent b may be used in an amount of from 0.5 to 4 molar equivalents, preferably from 1 to 3 molar equivalents, and more preferably from 1.5 to 2.5 molar equivalents as compared to starting material a.

The reaction is preferably conducted at a temperature of greater than 60 °C, preferably greater than 70 °C, and more preferably greater than 80 °C, for instance at a temperature of from 80 to 150 °C. Where the catalyst is a palladium catalyst, the temperature is even more preferably from 80 to 100 °C. Where the catalyst is a copper catalyst, the temperature is even more preferably from 100 to 120 °C. The reaction will typically be conducted at ambient pressure, i.e. a pressure of approximately 1 bar.

The reaction may be conducted for a period of at least 2 hours, such as for a period of from 4 to 24 hours.

Preferred combinations of catalysts and ligands, bases, solvents and reagent bs are as follows:

• Pd ₂ dba ₃ catalyst, with XPhos ligand, NaO/Bu base, toluene solvent, both L = Cl

• Pd ₂ dba ₃ catalyst, with XPhos ligand, K ₂ C0 ₃ base, tert- amyl alcohol solvent, both L = Cl

• Pd(dtbpf)Cl ₂ catalyst, no ligand, NaO/Bu base, toluene solvent, both L = Cl

• Pd(dtbpf)Cl ₂ catalyst, no ligand, K ₂ C0 ₃ base, tert- amyl alcohol solvent, both L =

Cl

• Pd ₂ dba ₃ catalyst, with XPhos ligand, NaO/Bu base, toluene solvent, both L = Br

• Pd ₂ dba ₃ catalyst, with XPhos ligand, K ₂ C0 ₃ base, tert- amyl alcohol solvent, both L = Br

• Pd(dtbpf)Cl ₂ catalyst, no ligand, NaO/Bu base, toluene solvent, both L = Br

• Pd(dtbpf)Cl ₂ catalyst, no ligand, K ₂ C0 ₃ base, tert- amyl alcohol solvent, both L =

Br

• CuCl catalyst, no ligand, NaH base, toluene solvent, both L = Cl

• CuCl catalyst, no ligand, NaH base, dimethylformamide solvent, both L = Cl

• CuCl catalyst, no ligand, Cs ₂ C0 ₃ base, dimethylformamide solvent, both L = Cl

• CuCl catalyst, ethanolamine ligand, Cs ₂ C0 ₃ base, dimethylformamide solvent, both L = Cl

• CuCl catalyst, (MeNH) ₂ C ₆ H4 ligand, Cs ₂ C0 ₃ base, dimethylformamide solvent, both L = Cl

• CuCl catalyst, no ligand, Cs ₂ C0 ₃ base, ethanolamine solvent, both L = Cl

In some embodiments, the reaction is carried out as a single reaction (i.e. with one set of reagents and under one set of conditions). However, in some embodiments, the reaction comprises the following sub-steps:

In other embodiments, the reaction comprises the following sub-steps:

d It will be appreciated that, in some instances, step (ii) will occur spontaneously on formation of intermediate c and step (ii’) will occur spontaneously on formation of intermediate c For the purposes of the present invention, these instances are considered to be embodiments in which the reaction is carried out as a single reaction.

In preferred embodiments, the sub-steps are earned out in the presence of different metal catalysts (/. e. sub-step (i) is earned out in the presence of a different metal catalyst to sub-step (ii), and sub-step (i’) is carried out in the presence of a different metal catalyst to sub-step (ii’)).

The sub-steps may be carried out in the presence of different ligands.

The sub-steps may be carried out under different conditions.

The methods of the present invention are preferably earned out on an industrial scale. For instance, where the method of preparing fuel additive d is a batch process, the fuel additive is preferably produced in a batch quantity of greater than 100 kg, preferably greater than 150 kg, and more preferably greater than 200 kg. The method may also be earned out as a continuous process.

In order to produce the fuel additive on an industrial scale, the reaction is preferably earned out in a reactor or, where the reaction comprises sub-steps (i) and (ii) or (i') and (ii’), reactors having a capacity of at least 500 L, preferably at least 750 L, and more preferably at least 1000 L. It will be appreciated that, where the reaction comprises sub-steps, more than one (e.g. each) sub-step may be carried out in the same reactor.

Octane-boosting fuel additive d

Fuel additives d that are prepared using the methods of the present invention have the following formula:

where: Ri is hydrogen;

R ₂ , R ₃ , R ₄ , R ₅ , R ₁₁ and R _l2 are each independently selected from hydrogen, alkyl, allcoxy, alkoxy-alkyl, secondary amine and tertiary amine groups; R ₆ , R ₇ , R ₈ and R ₉ are each independently selected from hydrogen, alkyl, alkoxy, alkoxy-alkyl, secondary amine and tertiary amine groups;

X is selected from -O- or -NR _l0 -, where R _l0 is selected from hydrogen and alkyl groups; and

n is 0 or 1,

provided that at least one of R ₂ , R ₃ , ₄ , R ₅ , R ₆ , R ₇ , R ₈ , R ₉ , R ₁₁ and R _l2 is selected from a group other than hydrogen.

Preferred substituents for the fuel additives are described below. It will be appreciated that the preferred substitution patterns also apply to the starting material a, reagent b, and intermediates c and c’ from which the fuel additive d is prepared.

In some embodiments, R ₂ , R ₃ , R ₄ , R ₅ , Rn and R _l2 are each independently selected from hydrogen and alkyl groups, and preferably from hydrogen, methyl, ethyl, propyl and butyl groups. More preferably, R ₂ , R ₃ , R ₄ , R ₅ , Rn and R ₃₂ are each independently selected from hydrogen, methyl and ethyl, and even more preferably from hydrogen and methyl.

In some embodiments, R ₆ , R ₇ , R ₈ and R ₉ are each independently selected from hydrogen, alkyl and alkoxy groups, and preferably from hydrogen, methyl, ethyl, propyl, butyl, methoxy, ethoxy and propoxy groups. More preferably, R ₆ , R ₇ , R ₈ and R ₉ are each independently selected from hydrogen, methyl, ethyl and methoxy, and even more preferably from hydrogen, methyl and methoxy.

At least one of R ₂ , R ₃ , R ₄ , R ₅ , R ₆ , R ₇ , R ₈ , R ₉ , Rn and R _l2 , and preferably at least one of R ₆ , R ₇ , R ₈ and R ₉ , is selected from a group other than hydrogen. More preferably, at least one of R ₇ and R ₈ is selected from a group other than hydrogen. Alternatively stated, the octane-boosting additive is substituted in at least one of the positions represented by R ₂ , R ₃ , R ₄ , R ₅ , R ₆ , R ₇ , R ₈ , R ₉ , Rn and R ₃₂ , preferably in at least one of the positions represented by R ₆ , R ₇ , R ₈ and R ₉ , and more preferably in at least one of the positions represented by R ₇ and R ₈ . It is believed that the presence of at least one group other than hydrogen may improve the solubility of the octane-boosting additives in a fuel.

Also advantageously, no more than five, preferably no more than three, and more preferably no more than two, of R ₂ , R ₃ , R ₄ , R ₅ , R ₆ , R ₇ , R ₈ , R ₉ , Rn and R _l2 are selected from a group other than hydrogen. Preferably, one or two of R ₂ , R ₃ , R ₄ , R ₅ , R ₆ , R ₇ , R ₈ , R ₉ , Rn and R _l2 are selected from a group other than hydrogen. In some embodiments, only one of R ₂ , R ₃ , R ₄ , R ₅ , R ₆ , R ₇ , R ₈ , R ₉ , Rn and R _l2 is selected from a group other than hydrogen. It is also preferred that at least one of R ₂ and R ₃ is hydrogen, and more preferred that both of R ₂ and R ₃ are hydrogen.

In preferred embodiments, at least one of R ₄ , R ₅ , R ₇ and Rg is selected from methyl, ethyl, propyl and butyl groups and the remainder of R ₂ , R ₃ , R ₄ , R ₅ , R ₆ , R , R ₈ , R ₉ , Rn and R _l2 are hydrogen. More preferably, at least one of R ₇ and Rg are selected from methyl, ethyl, propyl and butyl groups and the remainder of R ₂ , R ₃ , R ₄ , R ₅ , R ₆ , R ₇ , R ₈ , R ₉ , Rn and R _l2 are hydrogen.

In further preferred embodiments, at least one of R ₄ , R ₅ , R ₇ and R ₈ is a methyl group and the remainder of R ₂ , R ₃ , R ₄ , R ₅ , R ₆ , R ₇ , R ₈ , R ₉ , Rn and R _l2 are hydrogen. More preferably, at least one of R ₇ and Rg is a methyl group and the remainder of R ₂ , R ₃ , R ₄ , R ₅ , R ₆ , R ₇ , R ₈ , R ₉ , Rn and R _l2 are hydrogen.

Preferably, X is -O- or -NR _l0 -, where R _l0 is selected from hydrogen, methyl, ethyl, propyl and butyl groups, and preferably from hydrogen, methyl and ethyl groups. More preferably, Rio is hydrogen. In preferred embodiments, X is -0-.

n may be 0 or 1 , though it is preferred that n is 0.

Octane-boosting additives that may be used in the present invention include:

Preferred octane-boosting additives include:

Particularly preferred is the octane-boosting additive:

A mixture of additives may be used in the fuel composition. For instance, the fuel composition may comprise a mixture of:

It will be appreciated that references to alkyl groups include different isomers of the alkyl group. For instance, references to propyl groups embrace n-propyl and i-propyl groups, and references to butyl embrace n-butyl, isobutyl, sec-butyl and tert- butyl groups. Additive and fuel compositions

The present invention provides fuel additives d which are obtainable by a method of the present invention. Preferably, the fuel additives are obtained by a method according to the present invention.

The present invention also provides a process for preparing a fuel for a spark- ignition internal combustion engine, said process comprising: preparing a fuel additive d using a method of the present invention; and blending the fuel additive with a base fuel.

A fuel for a spark-ignition internal combustion engine is also provided. The fuel comprises a fuel additive d, obtainable and preferably obtained by a method of the present invention, and a base fuel.

Gasoline fuels (including those containing oxygenates) are typically used in spark- ignition internal combustion engines. Commensurately, the fuel composition that may be prepared according to the process of the present invention may be a gasoline fuel composition.

The fuel composition may comprise a major amount (/. e. greater than 50 % by weight) of liquid fuel (“base fuel”) and a minor amount (i.e. less than 50 % by weight) of additive composition of the present invention. Examples of suitable liquid fuels include hydrocarbon fuels, oxygenate fuels and combinations thereof.

The fuel composition may contain the octane-boosting fuel additive d in an amount of up to 20 %, preferably from 0.1 % to 10 %, and more preferably from 0.2 % to 5 % weight additive / weight base fuel. Even more preferably, the fuel composition contains the fuel additive in an amount of from 0.25 % to 2 %, and even more preferably still from 0.3 % to 1 % weight additive / weight base fuel. It will be appreciated that, when more than one octane-boosting fuel additive d is used, these values refer to the total amount of fuel additive e in the fuel.

The fuel compositions may comprise at least one other further fuel additive.

Examples of such other additives that may be present in the fuel compositions include detergents, friction modifiers/anti-wear additives, corrosion inhibitors, combustion modifiers, anti-oxidants, valve seat recession additives, dehazers/demulsifiers, dyes, markers, odorants, anti-static agents, anti-microbial agents, and lubricity improvers.

Further octane improvers may also be used in the fuel composition, i.e. octane improvers which do not have the structure of octane-boosting fuel additive d.

The fuel compositions are used in a spark-ignition internal combustion engine. Examples of spark-ignition internal combustion engines include direct injection spark- ignition engines and port fuel injection spark-ignition engines. The spark-ignition internal combustion engine may be used in automotive applications, e.g. in a vehicle such as a passenger car. The invention will now be described with reference to the following non-limiting examples.

Examples

Example 1 : Preparation of fuel additive d using palladium catalysts

Fuel additive d was prepared according to the following scheme:

90 °C

The fuel additive was prepared using the following procedure: to a set of reaction tubes (dimensions 110 mm x 17 mm) was weighed the catalysts and bases by use of a Mettler Toledo FlexiWeigh® automated solid dispenser. Separate tubes were used for the catalyst and for the base and internal standard.

To the catalyst tube containing Pd ₂ (dba) ₃ (14 mg, 0.016 mmol) and XPhos (30 mg, 0.062 mmol) was added tert- amyl alcohol (1 mL) and heated with stirring to 60 °C for 0.5 hours before cooling to ambient temperature. To each reaction tube of pre-weighed potassium carbonate as base (94 mg, 0.68 mmol) and di-/er/-butyl biphenyl (12 mg) as internal standard was added tert- amyl alcohol (2 mL) with stirring and the liquid reagents dichlorotoluene (80 pL; 0.62 mmol) and ethanolamine (75 pL, 1.24 mmol) added.

Subsequently, the 1 mL of pre-formed“Pd-XPhos” catalyst solution was charged to the main reaction tube and the resulting reaction mixture heated to 90 °C with a chilled- condenser head block to avoid solvent loss. Sampling of the reaction was conducted manually extracting an aliquot by syringe or Eppendorf pipette at 0, 2 and 16 hours.

The reaction was repeated using the same procedure, but modified in line with conditions in the following table:

Example 2: Preparation of fuel additive d using copper catalysts

Fuel additive d was prepared according to the following scheme:

The fuel additive was prepared using the following procedure: to a set of reaction tubes (dimensions 110 mm x 17 mm) was weighed the catalysts, bases and internal standard by use of a Mettler Toledo FlexiWeigh® automated solid dispenser. Separate tubes were used for the catalyst and for the base and internal standard.

To a tube of pre-weighed copper chloride catalyst (12 mg, 0.12 mmol), caesium carbonate (202 mg, 0.62 mmol) and di-/e/7-butylbiphenyl as internal standard (12 mg) was added dimethylformamide (2 mL) with stirring and the liquid reagents dichlorotoluene (80 mT, 0.62 mmol) and ethanolamine (75 pL, 1.24 mmol) charged. The resulting reaction mixture was heated to 110 °C with a chilled-condenser head block to avoid solvent loss and the reaction sampled manually by extracting an aliquot by syringe or Eppendorf pipette at 0, 2 and 16 hours.

The reaction was repeated using the same procedure, but modified in line with conditions in the following table:

The dimensions and values disclosed herein are not to be understood as being strictly limited to the exact numerical values recited. Instead, unless otherwise specified, each such dimension is intended to mean both the recited value and a functionally equivalent range surrounding that value. For example, a dimension disclosed as "40 mm" is intended to mean "about 40 mm.”

Every document cited herein, including any cross referenced or related patent or application, is hereby incorporated herein by reference in its entirety unless expressly excluded or otherwise limited. The citation of any document is not an admission that it is prior art with respect to any invention disclosed or claimed herein or that it alone, or in any combination with any other reference or references, teaches, suggests or discloses any such invention. Further, to the extent that any meaning or definition of a tern in this document conflicts with any meaning or definition of the same term in a document incorporated by reference, the meaning or definition assigned to that term in this document shall govern.

While particular embodiments of the present invention have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention. It is therefore intended to cover in the appended claims all such changes and modifications that are within the scope and spirit of this invention.