Sulfuric Acid → gamma-Cyhalothrin

Participants

Reaction Conditions

Reaction Steps

A 600 ml vacuum jacketed non-baffled split-neck reaction flask was equipped with a dual blade agitator. To the reactor, already containing a slurry of epimerisation mass as seed from a previous experiment (already˜⅔rds full), was charged the 1 R cyhalothrin (II) (166.3 g) in a mixture of isopropanol (99.9 g), water (3.09 g) and di-isopropylamine (5.22 g). The reaction mass was agitated at 100 rpm and −5° C. for 65 hr, before removing 251 g of reaction mass and transferring it to a 1 liter split-neck reaction vessel in an ice/water bath. To the 1 liter reaction vessel was charged hexane (60 ml) and sulphuric acid (47 ml of 50% w/w), and the resultant thick paste was agitated for 0.5 hr before diluting with hexane (350 ml) and water (350 ml). The mixture was heated to 55° C. for 30 min, then transferred to a separating funnel and the lower aqueous phase was separated off. The hexane solution was concentrated under reduced pressure to give the desired product as a viscous red/brown oil which solidified upon standing to give an off-white solid. The product weighed 151.2 g giving an estimated yield of 97% as gamma-cyhalothrin and a diastereomer ratio of 95:5.

Provenance & Evidence