KR0124948B1 - Process for organo isocyanate using 2-chlorobenzoxazolium salt - Google Patents

Abstract

2-Chloro-1-ethylbenzoxazolium tetrafluorobolate was reacted with aliphatic or aromatic hydroxamic acid in the presense of solvent such as dichloromethane, chloroform, acetonitril, diethylether, distilled wnder the reduced pressure to give isocyanate.

Description

Process for preparing organic isocyanate using 2-chloro benzoxazolium salt

The present invention is a method for producing isocyanate used to prepare diphenylmethane diisocyante (hereinafter referred to as MDI), which is an intermediate in the manufacture of polyurethane, and to synthesize anuginine, a physiologically active substance. The present invention relates to a method for preparing organic isocyanate by reacting substituted diphenyl carbonate with an aliphatic primary amine or an aromatic primary amine without using a highly toxic and highly corrosive phosgene gas.

To date, it is known that isocyanates are synthesized via various reaction routes. For example, first, a method of synthesizing isocyanates from the substitution reaction of haloalkyl and silvercyanate (Arch. Pharmacol., 302, 617 (1969)). In this case, the isocyanate can be synthesized from haloalkyl, but has the disadvantage that the isocyanate cannot be synthesized from haloaryl.

Second, the preparation of isocyanates by carbonylation of nitroalkyl (US Pat. Nos. 3,461,149, 3,673,827) requires high temperatures of 100 ° C. to 200 ° C. and high pressures of 100 to 250 atm.

Third, the classical preparation of isocyanates by phosgene gas of amines (British patent 1,086,782) is not only highly corrosive and toxic but also requires high reaction temperatures.

Fourth, the preparation method of isocyanate by Curtius method (J. Org. Chem., 38, 2982 (1973)) is a carbonyl azide made from the reaction of carbonylchloride and azide Isocyanate is prepared by heating or applying light, which has a risk of explosion due to heating of organic or inorganic azide.

Fifth, a method for preparing isocyanate by thermal decomposition of esters of carbamic acid (US Pat. No. 3,465,024) has a disadvantage of requiring a high temperature of 100 ° C to 500 ° C and a low yield.

Sixth, there is a method for producing isocyanate by Rosen rearrangement. This process yields significantly lower yields even though many of the isocyanates may or may not be produced by the Rosene potential reaction because most of the reactions do not stop at the isocyanate stage and are readily converted to amines.

The present invention reacts aliphatic or aromatic hydroxamic acid with 2-halo benzoxazolium salt in the presence of tertiary amine at room temperature to yield high yields of aliphatic or aromatic. ) Isocyanate can be produced.

The reaction scheme of the present invention is as follows.

Wherein R is an aliphatic or aromatic group, X is fluorine, chlorine or iodine and Et is an ethyl group.

In more detail, the present invention is reacted by adding an aliphatic or aromatic hydroxamic acid to 2-chloro-1-ethyl benzoxazolium tetrafluoro borate at room temperature and then reacting it under reduced pressure. Isocyanates were synthesized by distillation. These isocyanates were reacted with amines because of their high reactivity, and thus they were made into urea materials in stable form.

Any tertiary amine used in the present invention can be used, but triethylamine (triethylamine), pyridine (phridine), quinoline (quinoline) and quinoxaline (hexamethylenetetramine), 1.4-dia 1.4-diuzabicyclo (2.2.2) o (tane), 1,5-diazabicyclo (4.3.0) non-5-ene (1,5-diazabicyclo (4.3. 0) non-5-ene) and 1,8-diazabicyclo (5.4.0) undec-7-ene are particularly effective. In the general formula of the 2-chlorobenzoxazolium salt, X may be fluorine, chlorine, or iodine, and any solvent except for a protic solvent may be used as the solvent of the present invention, and dichlorormethane and chloroform. (chloroform), acetonitrile, diethylether, dimethyl carbonate, diethyl carbonate, and the like are useful. Is the temperature range from -40 ℃ good or between 100 ℃, especially from 0 ℃ 100 ℃ is preferred.

The present invention will be described in detail as examples. However, the present invention is not limited to this embodiment.

Example 1

26.9 grams of 2-chloro-1-ethyl benzoxazolium tetrafluoroborate and 7.51 grams of acetohydroxamic acid were placed in a 500 milliliter three-necked flask containing 200 ml of anhydrous dichloromethane and stirred with triethyl. Amine was added slowly. After stirring for 30 minutes, the solvent was removed and distilled under reduced pressure to obtain 4.9 grams of methylisocyanate. The reaction yield was 86.2%.

Example 2

26.9 grams of 2-chloro-1-ethyl benzoxazolium tetrafluoroborate and 13.7 grams of benzohydroxamic acid were placed in a 500 milliliter three-necked flask containing 200 ml of anhydrous acetonitrile and stirred with triethyl. The amine was slowly dropped. After stirring for 30 minutes, the solvent was removed and distilled under reduced pressure to obtain 10.7 grams of phenylisocyanate. The reaction yield at this time was 89.4%.

Example 3

17.3 grams of 2-chloro-1-ethyl benzoxazolium tetrafluoroborate and 17.3 grams of p-chloro phenyl hydroxamic acid are placed in a 500 ml three-necked round flask containing 200 ml of anhydrous dichloromethane. The triethylamine was gradually dropped while putting and stirring. After stirring for 30 minutes, the solvent was removed and distilled under reduced pressure to obtain 10.4 grams of phenyl isocyanate. The reaction yield at this time was 87.1%.

Example 4

26.9 grams of 2-chloro-1-ethyl benzoxazolium tetrafluoroborate and 17.3 grams of p-chlorophenylhydroxamic acid were placed in a 500 milliliter three-necked flask containing 200 ml of anhydrous dichloromethane, and the quinoline was slowly dropped. Knocked down. After stirring for 30 minutes, the solvent was removed and distilled under reduced pressure to obtain 10.5 grams of phenyl isocyanate. The reaction yield at this time was 88.2%.

Claims (2)

A method for producing an organic isocyanate, wherein the method of producing an organic isocyanate is reacted with a 2-chloro benzoxazolium salt of the following general formula and an aliphatic or aromatic hydroxamic acid at -40 ° C to 100 ° C in the presence of a tertiary amine. Wherein X is fluorine, chlorine or iodine and Et is an ethyl group. The method of claim 1, wherein the tertiary amine is triethylamine, pyridine, quinoline and quinoxaline, hexamethylene tetramine, 1,4-diazabicyclo (2.2.2) octane, 1,5-diazabicyclo ( 4.3.0) A process for producing organic isocyanates which are non-5-ene, 1,8-diazabicyclo (5.4.0) undec-7-ene.