US EPA

4119580 

Technical Report 

Investigation on phosphoric acid and thiophosphoric acid esters with a heterocyclic substituent, 10th and last communication: Aza-analogy II: Derivatives of oxazolo (4,5-b)pyridin-2(3H)-one, an aza-analogue of benzoxazol-2(3H)-one 

Ruefenacht, K; Kristinsson, H; Mattern, G 

1976 

HEEP/77/04639 

59 

5 

1593-1612 

HEEP COPYRIGHT: BIOL ABS. Oxazolo(4,5-b)pyridin-2(3H)-one, one of the possible aza-analog of benzoxazol-2(3H)-one, is readily prepared starting from furfural, using the Clauson-Kaas transformation (oxidative transformation of furans to pyridines with simultaneous incorporation of a nitrogen atom) and proceeding either via furfurylamine, 3-hydroxy-pyridine, 2-nitro- and 2-amino-3-hydroxy-pyridine followed by ring closure with phosgene or, on shorter routes, directly via 2-amino-3-hydroxy-pyridine or via alpha-methylamino-(fur-2-yl)-acetic acid amide and 3-hydroxypicolinic acid amide followed by a Hofmann degradation. Halogenation and nitration of oxazolo-(4,5-b)pyridin-2(3H)-one lead to the 6-substituted derivatives. A series of thiophosphoric and thiophosphonic acid esters with high insecticidal, acaricidal and anthelmintic activities and with extremely low mammalian toxicities up to and gt; 5000 mg/kg (rat per os) was disclosed via the N-hydroxymethyl and N-chloromethyl derivatives of the oxazolopyridin-ones and the thione. These esters are aza-analogs of the known benzoxazolone-insecticide type 1 and present really divergent properties. The vinyl compounds are easily accessible from the oxazolopyridin-ones with vinyl acetate. Addition of halogen to form the 3-(1,2-dihaloethyl)-derivatives occasionally is troublesome: 3-(2-halovinyl)-derivatives formed as inherent by-products by dehydrohalogenation handicap further reactions. Some thiophosphoric acid esters derived from the vinyl compounds and the dihaloethyl compounds, respectively are active pesticides too, but their mammalian toxicity ranges from 20-200 mg/kg (rat per os), values generally regular in the phosphoric ester field. The one-step condensation of a heterocyclic NH-compound, formaldehyde and a thiophosphoric compound (Staubli procedure) is not applicable to the preparation of the esters because the acidity of the oxazolopyridin-ones is too high to fulfill the basic requirements of this procedure. An alternative procedure running via the Mannich compounds fails due to salt formation between Mannich base and thiophosphoric acid. Ring-homologues such as the benzoxazinone derivatives and the pyrido-oxazinone derivatives are not pesticidal. The isomeric oxazolo(4,5-c)pyridin-2(3H)-one and oxazolo(5,4-b)pyridin-2(3H)-one could not be prepared.