DD254003A1 - METHOD FOR PRODUCING SUBSTITUTED OXAZOLIUM SALTS - Google Patents

Abstract

Such compounds are important as intermediates for the preparation of dyes, spectral sensitizers and as biologically active compounds. With the invention is to be achieved that substituted oxazolium salts in a simple manner and in high purity with good yields of readily available starting materials without the use of basic condensing agents are accessible. This is done according to the invention in such a way that a-aminoketones are reacted with acid chlorides or acid anhydrides, optionally in the presence of a dehydrating agent and a metal salt of a complex acid to the substituted oxazolium salts of general formula I. formula

Description

Such compounds are important as intermediates for the preparation of dyes, spectral sensitizers and as biologically active compounds.

Characteristic of the known technical solutions

It is known that oxazolium salts can be prepared by reaction of α-acylaminoketones with dehydrating agents such as POCl ₃ , acetic anhydride and perchloric acid or H ₂ SO ₄ at higher temperatures (R. Gompper, Chem. Ber. 90, 374 [1957]) ,

It is further known that oxazolium salts can be prepared by quaternization of oxazoles with suitable alkylating agents, such as methyl iodide or dialkyl sulfates (R.A. EFFREYS, J. Chem. Soc. 1952, [4923-32]).

The a-acylaminoketones required for the first-mentioned preparation are, as is also known, preparable by acylation of α-aminoketones with acid chlorides in the presence of a tertiary base, such as. As pyridine, by reaction of aminoketones with acetic anhydride at a higher temperature (K.VOIGT, J. f.pra. Chemistry / 2 /, 34.1 [1986]), or by the action of Raney nickel or organometallic compounds Oxazolones, which in turn are accessible by reaction of a- hydroxy ketones with carbonic acid amides at elevated temperature (R. Gompper, Chem. Ber. 90, 374 [1975]). The above methods have disadvantages, which in some cases must be passed through several stages in order to get from readily available starting materials to the desired target products, that reagents must be used, which, like the mentioned organometallic materials are not cheap and technically not safe to handle and that different condensing agents must be used as auxiliaries, which arise as a result of the synthesis as by-products or thermally unstable and lead to overheating spontaneous decomposition reactions, which in the case of using such condensing agent, the purity of the resulting products due to incidental decomposition reactions usually not very high and complicated purification operations are entailed (J. HEINZE, H. BAUMGÄRTEL, Chem. Ber. 103, 1572-77 [197O]).

The processes starting from corresponding oxazoles also have the disadvantage over the said deficiencies that they do not permit the preparation of N-aryl-substituted oxazolium salts or only produce 2-methyl-substituted oxazolium salts.

Object of the invention

The aim of the invention is to produce substituted oxazolium salts in a simple manner and in high purity with good yields from readily available starting materials without the use of basic condensing agents.

Explanation of the essence of the invention

The invention has for its object to produce substituted Oxazoliumsalze in a simple way from readily available starting materials in high purity and with good yields.

According to the invention, this object is achieved in that a-aminoketones of the general formula II

ff ³ v / 0

where R ^{1 is} an alkyl, cycloalkyl or preferably a substituted or unsubstituted aryl radical and R ³ , R ⁴ , which may be identical or different, denote hydrogen, an unsubstituted or substituted aryl or heteraroyl radical, with a carboxylic acid derivative of the formula III

R ² -CO-Y III

where R ^{2 is} a simple alkyl or an unsubstituted or substituted aryl or heteroaryl radical and Y is chloride or

an oxycarbonyl radical, in the presence of a condensing agent, such as acetic anhydride, POCl ₃ , H ₃ PO ₄ , polyphosphoric acid or H ₂ SO ₄ and a metal salt of a complex acid, preferably NaBF ₄ or NaCIO ₄ , at temperatures of 90-140 ⁰ C to oxazolium salts the general formula I, in which the radicals R ¹ , R ² , R ³ and R ^{4 have} the meaning given and X ~ is the anion of the acid salts assigned to the associated complex acid reacted.

The advantage of the process described here is that in a simple manner in a high purity and good yields in particular N-arylsubstituierte and thus z.T. previously mostly unknown oxazolium salts can be produced. The invention will be explained below in some embodiments.

2-methyl-3,5-diphenyloxazolium perchlorate la

0.1 mol Anilinoacetophenon are heated to boiling with 0.05 mol Mg (ClO _{4) 2} in 0.4 mol of acetic anhydride 3min, then is cooled to 60 ⁰ C and 2 mL of concentrated H ₃ PO ₄ was added. After cooling to room temperature, the precipitate is filtered off, washed with a little methanol and recrystallized from glacial acetic acid. This gives 0.093 mol la, which has a melting point of 234 ° C.

2-Methyl-3-phenyl-5-coumar-3'-yl-oxazolium perchlorate I b

0.1 mol of 3-anilinoacetylcoumarin is heated to boiling with 0.05 mol of Mg (CIO ₄ J ₂ in 0.5 mol of acetic anhydride for 5 min.) After cooling to 85 ° C., 3 ml of concentrated H ₃ PO _{4 are} added, after cooling Room temperature, the resulting precipitate is filtered off, washed with methanol and recrystallized from nitromethane to give 0.072 mol of Ib having a melting point of

2-ethyl-3 / p-bromophenyl / 4,5-diphenyloxazolium perchlorate Ic

0.1 mol of p-bromoanilinodeoxybenzoin is heated to boiling with 0.5 mol of propionic anhydride and 0.05 mol of Mg (CIO ₄ I _{2 for} 5 min.

It is then cooled to 80 ° C. and admixed with 4 ml of concentrated H ₃ PO ₄ O. After cooling to room temperature, the precipitate is filtered off with suction, washed with a little methanol and recrystallised from acetonitrile to give 0.083 ml of Ic with a melting point of 235 ° C.

Further oxazolium perchlorates of the formula type I (X = CIO ₄ ) prepared in analogous ways by using corresponding starting components are listed in Table 1.

No. R ¹ R ² R ³ R ⁴ Fp ₁ ( ⁰ C) Value (% of theory)

id C ₆ H ₅ C ₆ H ₅ 4-CH ₃ -C ₆ H ₄ CH ₃ 218 82 le C ₆ H ₅ C ₆ H ₆ 4-CI-C ₆ H ₄ CH ₃ 224-225 76 If C ₆ H ₅ · C ₆ H ₆ 4-Br-C ₆ H ₄ CH ₃ 215-218 91 ig C ₆ H ₅ C ₆ H ₅ 4-Br-C ₆ H ₄ CH ₃ 257-260 97 lh C ₆ H ₆ C ₆ H ₅ 4-NO ₂ -C ₆ H ₄ CH ₃ 260 57 ii C ₆ H ₅ C ₆ H ₅ 1-naphthyl CH ₃ 260 65 ij C ₆ H ₆ C ₆ H ₅ 4-CH ₃ -C ₆ H ₄ C ₂ H ₃ 241 83 Ik C ₆ H ₅ H 4-CH ₃ -C ₆ H ₄ CH ₃ 212 81 Il C ₆ H ₆ C ₆ H ₅ 4-CH ₃ -C ₆ H ₄ 4-CH ₃ OC ₆ H ₄ 260 73 in the C ₆ H ₅ H 4-CH ₃ OC ₆ H ₄ 4-CH ₃ -C ₆ H ₄ 260 79 In C ₆ H ₅ C ₆ H ₅ 4-CH ₃ OC ₆ H ₄ 4-CH ₃ OC ₆ H ₄ 260 62

No. R ¹ R ² R ³ R ⁴ 'm.p. ( ⁰ C) Yield (% of theory)

io C ₆ H ₅ CsH ₅ 4-CH ₃ OC ₆ H ₄ 4-CH ₃ -C ₆ H ₄ 260 91 ip C ₆ H ₅ C ₆ H ₅ 4-CH ₃ -C ₆ H ₄ 4-CH ₃ -C ₆ H ₄ 260 94 iq C ₆ H ₅ C ₆ H ₅ C ₆ H ₅ 260 93

Claims (1)

Process for the preparation of substituted oxazolium salts of the formula I, characterized in that a-aminoketones of the general formula II wherein R ^{1 is} an alkyl, cycloalkyl or preferably a substituted or unsubstituted aryl radical and R ³ , R ^{4 are} the same or different could be. Represent hydrogen, an unsubstituted or substituted aryl or heteroaryl radical, with a carboxylic acid derivative of the formula III in which R ^{2 is} a simple alkyl or a substituted or unsubstituted aryl or heteroaryl radical and Y is chloride or an oxycarbonyl radical, in the presence of a Condensing agent, such as acetone hydride, POCl ₃ , H ₃ PO ₄ , polyphosphoric acid or H 2 SO 4 and a metal salt of a complex acid, preferably NaBF ₄ or NaCIO ₄ , at temperatures of 90-140 ⁰ C, to the corresponding Oxazoliumsalzen Formei I, wherein R ¹ , R ² , R ³ and R ^{4 have} the abovementioned meaning and X ~ represents the anion of the complex acids associated with the metal salts added. Field of application of the invention The invention relates to a process for the preparation of substituted oxazolium salts of the type i