Process for the production of a phosphorus-containing organic compound

The present invention relates to a process for the production of phosphorus-containing organic compounds by the catalysed reaction between a phosphorus-containing oxide and an unsaturated hydrocarbon.

The Pudovik reaction is one of the most versatile pathways for the formation of carbon-phosphorus bonds and involves the addition of compounds containing a labile P—H bond with unsaturated systems such as alkenes, alkynes, carbonyls and imines as shown below:

The products of the reaction find significant applications in a wide range of areas, for example industrial, biological, and chemical synthetic uses. The Pudovik reaction can progress via a radical and/or an ionic mechanism. It appears in the literature that the difference in the Pudovik reaction mechanisms depends upon the nature of the unsaturated substrates. In fact, when the unsaturated substrate is an unsaturated system having a nucleophilic character, the mechanism is preferentially radical. In this case, photoactivation or chemical activation (peroxides, AIBN) is the most efficient method.

A problem associated with such methods is that the reaction time is long and experimental conditions are mostly drastic. Furthermore, the regioselectivity of the addition can be weak. More recently, ultrasound-induced radical reaction in homogeneous medium has been used. Indeed, when the unsaturated compound contains an electron-withdrawing substituent, the main mechanism is ionic. Diethylamine or potassium hydroxide is generally used and recently a tetramethylguanidine-catalyst has been employed efficiently under mild conditions. In the presence of free radical initiators or under photochemical or ultrasound irradiation in homogeneous medium, the phosphorylated reagents (R 2 P(O)H) add to the double bond by a free radical mechanism and the orientation is anti-Markovnikov. In basic medium, the addition occurs by nucleophilic attack of phosphorus anions to olefins by a Michael type mechanism and the orientation is also anti-Markovnikov.

It is known to produce phosphorus-containing organic compounds through the reaction of a phosphine oxide and an unsaturated hydrocarbon as is evidenced by DE 2849003, DE 2516341 and DE 2516343. The reactions used in the processes of these patent applications are carried out at a temperature in excess of 100° C. and require an initiator. Furthermore, unwanted by-products are produced which have to be separated at the end of the synthesis route, thereby adding an additional step to the process.

We have found that phosphorus-containing organic compounds can be prepared by a simple synthesis route that does not produce substantial undesired by-products and can be carried out under less severe reaction conditions.

Accordingly, the present invention provides a process for the production of organic phosphorus-containing products having the general formula (I)

wherein:

R 1 and R 2 are each independently alkyl, aryl, hydroxy, O-alkyl or O-aryl;

R 3 , R 4 , R 5 and R 6 are each independently hydrogen, alkyl, aryl, R 7 OH, R 8 CN, R 9 NXY, or CH(CH 2 ) n OR 10 OR 11 ;

R 7 is CH 2 , CH(CH 2 ) n or CH(OH)(CH 2 ) n ;

R 8 is CH 2 , CH(CH 2 ) n or CH(OAc)(CH 2 ) n and,

R 9 is CH(CH 2 ) n or CHCO 2 R 12 , where R 12 is hydrogen, alkyl or aryl;

X and Y are independently selected from hydrogen, alkyl, aryl or ester;

R 10 and R 11 are the same or different and may be hydrogen, alkyl or aryl or the two groups may be linked by (CH 2 ) n to form a cyclic ring; and

n is from 0 to 12,

which comprises reacting a phosphorus-containing oxide of general formula (II)

wherein the various symbols are as defined above with an unsaturated hydrocarbon of general formula (III)

wherein the various symbols are as defined above, in the presence of a boron-containing compound and at a temperature of less than or equal to 50° C.

The process of the present invention provides the advantage over the known prior art in that the reaction conditions are less severe and there are substantially no unwanted by-products.

The process of the present invention involves reacting a phosphorus-containing oxide of general formula (II) with a unsaturated hydrocarbon. R 1 and R 2 of compound (II) may be the same or may be different and may be selected from alkyl, aryl, hydroxy, O-alkyl or O-aryl. Where R 1 or R 2 is alkyl or O-alkyl, the alkyl group may be C 1 to C 6 alkyl, for example C 1 to C 3 alkyl, for instance methyl. Where R 1 or R 2 is aryl or O-aryl, the aryl group may be phenyl or substituted phenyl, for example halo phenyl, alkoxy phenyl or alkyl phenyl. An example compound for use in the present process is where R 1 and R 2 are independently methyl or phenyl.

As regards the unsaturated hydrocarbon compound, this compound may be, for example, an alkene, an allylic acid, an allylic alcohol, an allylic-alpha-acetoxy nitrile or an alpha amino acid vinyl such as D or L-vinylglycine. In particular, R 3 , R 4 , R 5 and R 6 of general formula (III) may be the same or may be different and may be selected from H, alkyl, aryl, R 7 OH or R 8 CN, R 9 NXY, or CH(CH 2 ) n OR 10 OR 11 . Where R 3 , R 4 , R 5 and/or R 6 is alkyl, this may be C 1 to C 12 alkyl, for example C 1 to C 6 alkyl, for instance methyl. Where R 3 , R 4 , R 5 and/or R 6 is an alcohol functionality of the formula R 7 OH, R 7 is CH 2 , CH(CH 2 ) n or CH(OH)(CH 2 ) n where n is from 0 to 12, for example from 1 to 6. Where R 3 , R 4 , R 5 and/or R 6 is a cyano functionality of the formula R 8 CN, R 8 is CH 2 , CH(CH 2 ) n or CH(OAc)(CH 2 ) n , where n is from 0 to 12, for example from 1 to 6. Where R 3 , R 4 , R 5 and/or R 6 is a nitrogen functionality of the formula R 9 NXY, R 9 is, for example, CHCO 2 R 12 , where R 12 may be selected from hydrogen, alkyl or aryl, and X and Y are independently selected from hydrogen, alkyl, aryl or ester. Where R 3 , R 4 , R 5 and/or R is CH(CH 2 ) n OR 10 OR 11 , R 10 and R 11 may be the same or different and may be hydrogen, alkyl or aryl or the two groups may be linked by (CH 2 ) n to form a cyclic ring. The alkyl and aryl groups and n are as herein before defined.

The phosphorus-containing oxide and the unsaturated hydrocarbon may be reacted in any suitable amount to allow reaction. The amount of oxide to unsaturated hydrocarbon may be, for example, in a ration 2 to 1 or 1 to 1, for instance the two reactants may be present in stoichiometric amounts.

The process of the present invention is carried out in the presence of a boron compound. Suitable boron compounds are alkyl boranes such as methyl, ethyl and propyl. An example compound is triethyl borane. The boron compound may be present in an amount of, for example, from 1 to 30% molar concentration, for instance from 5 to 20%.

The process may be carried out in the presence of a solvent. Suitable solvents include alcohols, for example methanol; hydrocarbons, for example hexane; nitrites, for example acetonitrile; and ketones, for example acetone. The solvent in the process may be, for example, an alcohol such as methanol. The solvent may be present in the reaction medium in an amount of, for example, from 0 to 150 equivalents, for instance from 20 to 60 equivalents.

The process is carried out at a temperature of less than or equal to 50° C., for example less than or equal to 20° C. For instance, the process can be operated at a temperature of from (minus) −20 to (plus) +20° C., for example from −15 to +20° C.

The compounds of formula (I) have one or more of the following uses: use as intermediates for the manufacture of flameproofing agents, flame retardants for polymers, solvents for dyes, extractants for metals from aqueous solutions, and use as biologically active compounds having bactericidal, fungicidal or herbicidal action.

The process of the present invention will now be illustrated with reference to the following examples: