1.  Field of the Invention
The present invention is directed to a new class of 2-(tetrahydro-2-thienyl)phenyl esters of phosphorothioic acid.  More particularly, the instant invention is directed to a class of 2-(tetrahydro-2-thienyl)phenyl esters of phosphorothioic acid useful as insecticides. 
2.  Background of the Prior Art
The devastation caused by pests represents a serious economical threat to commercially important food, fiber and ornamental plants.  Particularly serious is the attack of pests against important grain plants such as corn and rice.  For this reason the development of new, more effective pesticides represents an ongoing scientific activity.  It is particularly important to develop pesticides effective at very low dosages.  Such pesticides provide necessary control without attendant environmental difficulties. 
Esters of phosphorothioic acids, that is, phosphorothioates, are well known in the art.  Several disclosures of these esters, which allege insecticidal, acaricidal and/or nematocidal utility, are available in the art.  For example, U.S. Pat.  No.  2,599,516 issued to Moyle discloses O,O-dimethyl or O,O-diethyl O-2,4,5-trichlorophenyl phosphorothioates.  These compounds are said to possess systemic insecticidal properties and provide effective control of flies and other household pests. 
U.S. Pat.  No.  2,761,806 issued to Boyer sets forth a class of O-chloro-substituted phenyl O,O-dialkyl phosphorothioates useful as non-systemic nematocides.  These phosphorothioates are alleged to also be effective as soil insecticides. 
U.S. Pat.  No.  3,042,703 issued to Schegk et al.  is of particular interest, directed as it is to a class of thiophosphoric acid esters.  The species, O,O-dialkyl O-4-(methylthio or methylsulfinyl)phenyl phosphorothioate, is useful as an insecticide and particularly as a nematocide, active against free-living, cyst-forming and root-knot nematodes. 
Another class of non-systemic insecticides are the O-(4-bromo-2,5-dichlorophenyl) O,O-dialkyl phosphorothioates described in U.S. Pat.  No.  3,275,718 issued to Sehring et al. 
The compound O,O,O',O'-tetramethyl O,O'-thiodi-p-phenylene phosphorothioate is the subject of U.S. Pat.  No.  3,217,636 issued to Lovell et al.  This compound is recited, in the `636 patent, to be effective in controlling cutworms, thrips on citrus and Lygus bugs. 
Another class of phosphoric and phosphonic acid esters are recited to be useful as insecticides, fungicides, acaricides, nematocides and molluscicides.  This class of esters is taught in U.S. Pat.  No.  3,468,984 issued to Beriger.  The '984 patent particularly discloses O-2,5-dichloro-4-iodophenyl O,O-dimethyl phosphorothioate as a non-systemic contact and stomach insecticide and acaricide. 
Finally, U.S. Pat.  No.  3,600,472 issued to Sehring et al.  describes O-(2,5-dichloro-4-alkylmercaptophenyl)phosphorothioates and analogous phosphorothioates useful as insecticides and acaricides.  Particularly interesting is the compound, O-2,5-dichloro-4-(methylthio)phenyl O,O-diethyl phosphorothioate. 
All of the phosphorothioates described in the above references having pesticidal activity are structurally distinguished from esters of 2-(tetrahydro-2-thienyl)phenyl phosphorothioic acid. 
The above remarks establish the absence in the art of an important class of pesticides, the esters of 2-(tetrahydro-2-thienyl)phenyl phosphorothioic acid.