The invention herein described relates to a new compound, 2-azabicyclo[2.2.1]hept-5-ene-2-acetic acid, the preparation of said new compound and its use as an intermediate in the process for the manufacture of N-phosphonomethylglycine, a known herbicide and plant growth regulator.
Methyl-2-azabicyclo[2.2.1]hept-5-ene-2-acetate (azanorbornene methyl ester) was described in the literature by Paul A. Grieco in J. Am. Chem. Soc., 1987, 109, pp 5859-5861 and J. Org. Chem. 1987, 52, pp 5746-5749. However, 2-azabicyclo[2.2.1]-hept-5-ene-2-acetic acid, the compound and its formation by an Aza Diels-Alder reaction in glacial acetic acid has not been reported in the literature.
N-Phosphonomethylglycine, the compound and its use as an important herbicidal agent is described in U.S. Pat. No. 3,799,758. N-phosphonomethylglycine and derivatives thereof are effective herbicides at low rates of application when applied postemergence and are biodegradable into harmless residues within a relatively short period of time after their application.
A number of processes for the preparation of N-phosphonomethylglycine have been described in a series of patents such as U.S. Pat. Nos. 4,053,505, 4,237,065, 4,415,503, and 4,428,888 among others. Many of these processes use glycinate esters or phosphinate esters, or both, necessitating additional materials and additional reaction steps for their formation.
There is an ongoing search in the art for better methods of preparation of this agronomically important compound. Surprisingly, it has been discovered that 2-azabicyclo[2.2.1]hept-5-ene-2-acetic acid (N-carboxymethylazanorbornene), derivatives thereof and related compounds can be used as key intermediates in a new and useful process to prepare N-phosphonomethylglycihe. It is an object of the present invention to describe a novel compound and its preparation and to provide a new and useful method to prepare N-phosphonomethylglycine. This novel intermediate allows the preparation of N-phosphonomethylglycine from glycine and PCl.sub.3 without the use of esters.