Disclosed are a pyrazole compound or a salt thereof, a preparation method therefor, a herbicidal composition and use thereof. The pyrazole compound or a salt thereof has a structure as shown in formula (I):

##STR00001##

wherein, R represents

##STR00002##

wherein, R, R, and R represent hydrogen, C1-C4 alkyl, C1-C4 halogenated alkyl, C1-C4 alkoxy or halogen, R, R, and R may be the same or different; R.sub.1 represents C1-C3 alkyl; R.sub.2 represents hydrogen or C1-C4 alkyl; R.sub.3 represents hydrogen or C1-C6 alkyl, optionally substituted phenyl, optionally substituted pyridyl, optionally substituted alkenyl, optionally substituted alkynyl, C1-C6 alkyl carbonyl, C1-C6 alkoxyl carbonyl, C1-C6 alkyl carbonyl methyl, etc. A compound having a pyrazole structure not only has excellent herbicidal effect on barnyard grass, but also is safe to rice in post-emergence application. More surprisingly, it also has good control efficacy on barnyard grass resistant to major herbicides, such as penoxsulam, quinclorac, cyhalofop-butyl, propanil, etc.

Disclosed are a pyrazole compound or a salt thereof, a preparation method therefor, a herbicidal composition and use thereof. The pyrazole compound or a salt thereof has a structure as shown in formula (I):

##STR00001##

wherein, R represents

##STR00002##

wherein, R, R, and R represent hydrogen, C1-C4 alkyl, C1-C4 halogenated alkyl, C1-C4 alkoxy or halogen, R, R, and R may be the same or different; R.sub.1 represents C1-C3 alkyl; R.sub.2 represents hydrogen or C1-C4 alkyl; R.sub.3 represents hydrogen or C1-C6 alkyl, optionally substituted phenyl, optionally substituted pyridyl, optionally substituted alkenyl, optionally substituted alkynyl, C1-C6 alkyl carbonyl, C1-C6 alkoxyl carbonyl, C1-C6 alkyl carbonyl methyl, etc. A compound having a pyrazole structure not only has excellent herbicidal effect on barnyard grass, but also is safe to rice in post-emergence application. More surprisingly, it also has good control efficacy on barnyard grass resistant to major herbicides, such as penoxsulam, quinclorac, cyhalofop-butyl, propanil, etc.

The present invention provides new stable crystalline N-iodoamides-1-iodo-3,5,5-trimethylhydantoin (1-ITMH) and 3-iodo-4,4-dimethyl-2-oxazolidinone (IDMO). The present invention further provides a process for the preparation of organic iodides using N-iodoamides of this invention and recovery of the amide co-products from waste water.

The present invention provides new stable crystalline N-iodoamides-1-iodo-3,5,5-trimethylhydantoin (1-ITMH) and 3-iodo-4,4-dimethyl-2-oxazolidinone (IDMO). The present invention further provides a process for the preparation of organic iodides using N-iodoamides of this invention and recovery of the amide co-products from waste water.