7-(4,6-Dimethoxypyrimidinyl)oxy- and -thiophthalides as novel herbicides: Part 1. CGA 279 233: a new grass-killer for rice.

A series of novel types of 7-(4,6-dimethoxypyrimidin-2-yl)oxy- and -thio-3-methyl-1 (3H)-isobenzofuranones were discovered at Dr R Maag AG. From the thio-isobenzofuranyl series, CGA 279 233--BSI-proposed common name pyriftalid--was chosen for further development as a grass herbicide for use in rice. General synthetic approaches to these new phthalic acid-derived compounds are given, with emphasis on the synthesis of pyriftalid and its physico-chemical behaviour.