Broad-spectrum isothiazole antimicrobial agents

Antimicrobial compounds of formula I, II, or III ##STR7## wherein R.sub.1 and R.sub.2 are independently selected from hydrogen, halogen, or (C.sub.1 -C.sub.4)alkyl;

• R.sub.1 and R.sub.2 may be taken together with the carbons to which they are attached to form a 5 to 7-membered carbocyclic ring and the ring may be aromatic;
• R.sub.3 is hydrogen, (C.sub.1 -C.sub.8)alkyl, (C.sub.2 -C.sub.8)alkenyl, (C.sub.2 -C.sub.8)alkynyl, (C.sub.5 -C.sub.7)cycloalkyl or cycloalkenyl, phenyl or phenyl substituted with a substituent selected from (C.sub.1 -C.sub.3)alkyl, (C.sub.1 -C.sub.3)alkoxy, hydroxy, nitro, halo, cyano, and (C.sub.1 -C.sub.3)alkylthio, (C.sub.7 -C.sub.10)aralkyl or (C.sub.7 -C.sub.10)aralkyl substituted with a substituent selected from (C.sub.1 -C.sub.3)alkyl, (C.sub.1 -C.sub.3)alkoxy, hydroxy, nitro, halo, cyano, and (C.sub.1 -C.sub.3)alkylthio, or a 5 to 8-membered heteroaryl having one or more heteroatoms selected from the group consisting of oxygen and sulfur;
• R.sub.4 is an electron-withdrawing group selected from CN, NO.sub.2, P(C))(OR.sub.7).sub.2, P(S)(OR.sub.7).sub.2, COOR.sub.6, COR.sub.6, CONHR.sub.6, SOR.sub.6, SO.sub.2 R.sub.6, where R.sub.6 is hydrogen, (C.sub.1 -C.sub.8)alkyl, phenyl or substituted phenyl, (C.sub.7 -C.sub.10)aralkyl or substituted (C.sub.7 -C.sub.10)aralkyl, (C.sub.5 -C.sub.7)cycloalkyl, or a 5 to 8-membered heteroaryl having one or more heteroatoms selected from the group consisting of oxygen and sulfur;
• and where R.sub.7 is (C.sub.1 -C.sub.4)alkyl or phenyl;
• R.sub.3 and R.sub.4 may be joined to form a (C.sub.5 -C.sub.7)cycloalkenone optionally containing a heteroatom selected from the group consisting of oxygen and sulfur;
• R.sub.5 is hydrogen or (C.sub.1 to C.sub.4)alkyl;
• and
• Y is oxygen, sulfur, sulfoxide, or sulfone substituted with (C.sub.1 -C.sub.4)alkyl, (C.sub.3 -C.sub.5)cycloalkyl, or phenyl.