PURPOSE: To obtain the subject compound having a prochiral benzopyran ring, having an excellent selective herbicidal activity especially against paddy rice, soybean and cotton, and useful as a herbicide.
CONSTITUTION: This prochiral benzopyran derivative is a compound of formula I (R1 is a lower alkyl; R2 is a lower alkyl, a lower alkoxy, a halogen or a lower alkyl substituted with a halogen; R3 is R2, a lower alkoxy substituted with a halogen, etc.; R4 is a (substituted) alkyl; R5 is H or a lower alkyl; R4 and R6 may combine to form a carbonyl or thiocarbonyl; (m), (n) are each 0-4], e.g. (2R,3S,3aS,9bR)-3-(2-chlorobenzyloxy)-5bromomethyl-2-ethyl-5-methyl-3,3 a,5,9b-tetrahydro-2H-pro[3,2-C] [2]benzopyran. Further, to obtain this compound, it is preferable e.g. to react the compound of formula II in an inert solvent such as n-hexane in the presence of e.g. tin tetrachloride at (-)70-30°C reaction temperature.
ARAI SEIJI
KAKIMOTO TAKESHI
EDA SADAFUMI
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