Synthesis of (2-nitro)alkyl (meth)acrylates via transesterification of (meth)acrylate esters

Abstract

Provided is a process for making (2-nitro)alkyl (meth)acrylate compounds of formula I: wherein n, R, R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.6, R.sup.7, and n are as defined herein, by a transesterification reaction between a nitroalcohol compound and a (meth)acrylate compound in the presence of a transesterification catalyst and a free radical inhibitor. ##STR00001##

Claims

1. A process for making a compound of formula I: ##STR00041## wherein n is from 0 to 100; R is H or CH.sub.3; R.sup.1 and R.sup.2 are independently H, linear or branched C.sub.1-C.sub.8 alkyl optionally substituted with NO.sub.2, or R.sup.1 R.sup.2 together with the carbon atom to which they are attached form C.sub.3-C.sub.12 cycloalkyl; R.sup.3 and R.sup.4 are independently H, linear or branched C.sub.1-C.sub.8 alkyl, or a group of formula C(R.sup.1)(R.sup.2)OR.sup.5, wherein R.sup.5 is H or C(O)C(R)CH.sub.2, or R.sup.3 and R.sup.4, together with the carbon atom to which they are attached, form C.sub.3-C.sub.12 cycloalkyl; and R.sup.6 and R.sup.7 when present are independently H or CH.sub.3, the process comprising: transesterifying a nitroalcohol compound of formula II: ##STR00042## wherein R.sup.1, R.sup.2, R.sup.6, R.sup.7, and n are the same as in formula I; and R.sup.3 and R.sup.4 are independently H, linear or branched C.sub.1-C.sub.8 alkyl, or a group of formula C(R.sup.1)(R.sup.2)OH, or R.sup.3 and R.sup.4, together with the carbon atom to which they are attached, form C.sub.3-C.sub.12 cycloalkyl, with a (meth)acrylate of formula III: ##STR00043## wherein R is the same as in formula I; and R.sup.8 is linear or branched C.sub.1-C.sub.8 alkyl, in the presence of a transesterification catalyst and a free radical inhibitor to form the compound of formula I, wherein the transesterification catalyst is a basic catalyst, a zirconium complex, a hafnium complex, or mixtures thereof, and wherein the transesterification is conducted at a temperature of from 70 to 125 C. and a pressure of 400 mm Hg to 760 mm Hg.

2. The process of claim 1 wherein the transesterification catalyst is a zirconium complex, a hafnium complex, or a mixture thereof.

3. The process of claim 1 wherein the transesterification catalyst is a hafnium complex.

4. The process of claim 1 wherein the transesterification catalyst is a zirconium complex.

5. The process of claim 1 wherein the mole ratio of (meth)acrylate compound to nitroalcohol is from 1:1 to 20:1.

6. The process of claim 1 wherein excess (meth)acrylate and its corresponding alcohol form an azeotropic mixture and wherein this byproduct alcohol is removed by azeotropic distillation.

7. The process of claim 1 wherein the free-radical inhibitor is, phenothiazine, hydroquinone, methyl ether of hydroquinone, 4-Hydroxy-TEMPO, or mixtures thereof.

8. The process of claim 1 wherein R.sup.1 is H and R.sup.2 is H or linear or branched C.sub.1-C.sub.8 alkyl optionally substituted with NO.sub.2.

9. The process of claim 1 wherein R.sup.3 and R.sup.4 are independently linear or branched C.sub.1-C.sub.8 alkyl, or R.sup.3 and R.sup.4, together with the carbon atom to which they are attached, form C.sub.3-C.sub.12 cycloalkyl.

10. The process of claim 1 wherein the compound of formula I is: 2-methyl-2-nitropropyl acrylate; 2-methyl-2-nitropropyl methacrylate; 2-nitrobutyl acrylate; 2-nitrobutyl methacrylate; 2-methyl-2-nitropropane-1,3-diyl diacrylate; 2-methyl-2-nitropropane-1,3-diyl bis(2-methylacrylate); 3-hydroxy-2-methyl-2-nitropropyl acrylate; 3-hydroxy-2-methyl-2-nitropropyl methacrylate; 2-ethyl-2-nitropropane-1,3-diyl diacrylate; 2-ethyl-2-nitropropane-1,3-diyl bis(2-methylacrylate); 2-(hydroxymethyl)-2-nitrobutyl acrylate; 2(hydroxymethyl)-2-nitrobutyl methacrylate; 3-hydroxy-2-(hydroxymethyl)-2-nitropropyl acrylate; 3-hydroxy-2-(hydroxymethyl)-2-nitropropyl methacrylate; 2-(hydroxymethyl)-2-nitropropane-1,3-diyl diacrylate; 2-(hydroxymethyl)-2-nitropropane-1,3-diyl bis(2methylacrylate); 3-nitrooctan-4-yl acrylate; 3-nitrooctan-4-yl methacrylate; 2-((acryloyloxy)methyl)-2-nitropropane-1,3-diyl diacrylate; 2-((methacryloyloxy)methyl)-2-nitropropane-1,3-diyl bis(2-methylacrylate); 2-methyl-2-nitrobutyl acrylate; 2-methyl-2-nitrobutyl methacrylate; (1-nitrocyclohexyl)methyl acrylate; (1-nitrocyclohexyl)methyl methacrylate; 1-(nitromethyl)cyclohexyl acrylate; 1-(nitromethyl)cyclohexyl methacrylate; 2,5,6-trimethyl-2,6-dinitroheptan-3-yl acrylate; or 2,5,6-trimethyl-2,6-dinitroheptan-3-yl methacrylate, or an alkoxylated derivative thereof.

11. The process of claim 1 wherein R.sup.1 is H and R.sup.2 is H or linear or branched C.sub.1-C.sub.6 alkyl optionally substituted with NO.sub.2.

12. The process of claim 1 wherein R.sup.1 is H and R.sup.2 is H.

13. The process of claim 1 wherein R.sup.1 and R.sup.2 together with the carbon atom to which they are attached, form a cyclohexyl group.

14. The process of claim 1 wherein R.sup.3 and R.sup.4 together with the carbon atom to which they are attached, form a cyclohexyl group.

15. The process of claim 4 wherein R.sup.1 is H and R.sup.2 is H or R.sup.1 and R.sup.2 together with the carbon atom to which they are attached, form a cyclohexyl group; the transesterification catalyst is present at a concentration of 0.1 to 10 mol %.; and n is 0.

16. The process of claim 1 wherein the transesterification catalyst is zirconium acetyl acetonate.

17. The process of claim 1 wherein the transesterification catalyst is a basic catalyst.

18. The process of claim 17 wherein the transesterification catalyst is lithium hydroxide.

Description

EXAMPLES

Example 1

Synthesis of 2-Nitro-2-Methylpropyl Methacrylate

(1) ##STR00037##

(2) Procedure I: To a 1000 ml 4 necked flask fitted with a stirrer, thermometer, 10-tray distillation head and a reflux splitter was added 2-nitro-2 methyl propanol (123.5 g, 1.04 mol) and toluene (350 ml). The resulting mixture was heated to 100 C. under reduced pressure (400 mmHg) and approximately 30 ml of distillate was collected in the receiver in order to dry the contents of the flask via an azeotrope formed between water and the solvent. Then heating turned off and the pot solution was allowed to cool 50-60 C. To the solution were added phenothiazine (115 mg), methyl methacrylate, MMA, (119 g, 1.2 mol) and zirconium acetyl acetonate (7.25 g, 0.015 mol). The reaction mixture was heated to 120 C. under reduced pressure (700 mmHg). Reflux/distillation splitter was set at 20/5 and the distillate was collected when the vapor temperature was between 65-70 C. over a 4.5 hour period, weighed accurately and analyzed by quantitative .sup.1H-NMR. The amount MeOH byproduct formed was calculated from this analysis and it revealed approximately 75% of starting nitro alcohol was converted. It also indicated that approximately 21 g of MMA was lost to the distillate. To the reaction was added MMA (20 g, 0.2 mol) and more zirconium acetyl acetonate (2.25 g, 0.005 mol). Heating continued for at 120 C. another 4 hrs during which approximately 58 g of distillated was collected and .sup.1H-NMR analysis of reaction mixture revealed 87% conversion of nitro alcohol. To the reaction mixture was added MMA (26 g, 0.26 mol) and zirconium acetyl acetonate (2 g, 0.004 mol). Heating continued for another 2 hrs after which toluene and unreacted excess MMA were removed in a rotary evaporator to yield 184.5 g. The crude product showed greater than 80% purity by .sup.1H-NMR. Major impurities were toluene (7%), unreacted alcohol starting material (10%) and MMA (2%). Product yield was 77%.

(3) Procedure II: To a 1000 ml 4 necked flask fitted with a stirrer, thermometer, 10-tray distillation head and a reflux splitter was added 2-nitro-2-methyl propanol (119 g, 1 mol) phenothiazine (70 mg) and MMA (350 ml). The resulting mixture was heated to 100 C. under reduced pressure (400 mmHg). Heating turned off after 50 ml of MMA was collected and the pot solution was allowed to cool to 50-60 C. To the solution was added zirconium acetyl acetonate (7.25 g, 0.015 mol). The resulting solution was heated to 100 C. and the distillate was collected at reduced pressure 495 mmHg After 6 hrs of reaction time distillation vapor temperature began to fall from the peak temperature of 70 C.

(4) Approximately 150 g of distillate was collected and 1H-NMR analysis of the pot revealed 89% conversion of starting nitro alcohol. To the reaction was added MMA (25 g, 0.25 mol) and zirconium acetyl acetonate (0.25 g, 0.5 mmol). Heating continued for another 2 hrs and .sup.1H-NMR analysis of reaction mixture revealed no changes of nitro alcohol. Excess MMA and unreacted nitro alcohol starting material were removed by vacuum distillation (Pot temp. 93 C., vapor Temp. 82-87 C., pressure 3 mmHg), to give >95% pure monomer, weighing 150 g, with an overall yield of 75%.

Example 2

Synthesis of 2-Methyl-2-Nitropropane-1,3-Diyl Bis(2-Methylacrylate) (Prophetic)

(5) ##STR00038##

(6) 2-Methyl-2-nitropropane-1,3-diyl bis(2-methylacrylate) may be prepared using essentially the same procedures as described in Example 1 except for substituting 2-methyl-2-nitropropane-1,3-diol as the starting nitroalcohol compound, doubling the number of equivalents of methyl methacrylate, and making other non-critical modifications as needed.

Example 3

Synthesis of 2-(Methacryloyloxy)methyl)-2-Nitropropane-1,3-Diyl Bis(2-Methylacrylate) (Prophetic)

(7) ##STR00039##

(8) 2-(Methacryloyloxy)methyl)-2-nitropropane-1,3-diyl bis(2-methylacrylate) may be prepared using essentially the same procedures as described in Example 1 except for substituting 2-(hydroxymethyl)-2-nitropropane-1,3-diol as the starting nitroalcohol compound, tripling the number of equivalents of methyl methacrylate, and making other non-critical modifications as needed.

Example 4

Synthesis of (1-Nitrocyclohexyl)methyl Methacrylate (Prophetic)

(9) ##STR00040##

(10) (1-Nitrocyclohexyl)methyl methacrylate may be prepared using essentially the same procedures as described in Example 1 except for substituting (1-nitrocyclohexyl)methanol as the starting nitroalcohol compound and making non-critical modifications as needed.