A compound of Formula I: wherein R 1 is: C 1 -C 6 alkyl optionally substituted with 1-3 R 4; -C(=O)R 5; or -CH 2 OC(=O)R 5; R 2 is: C 1 -C 6 alkyl optionally substituted with 1-3 R 6; -C(=O)R 7; -C(=O)OR 7; or -(CHR 8) n R 7; wherein n is an integer from 1-3; R 3 is -S 2 R 9; R 4 is independently C 1 -C 6 alkyl, C 1 -C 4 alkoxy, C 1 -C 4 haloalkoxy, C 1 -C 4 alkylthio, C 1 -C 4 haloalkylthio, amino, C 1 -C 3 alkylamino, C 2 -C 6 alkoxycarbonyl, C 2 -C 6 alkylcarbonyl, C 2 -C 6 alkylaminocarbonyl, hydroxyl, deuterium, or C 3 -C 6 trialkylsilyl; R 5 is H, C 1 -C 6 alkyl, C 2 -C 6 alkenyl, C 3 -C 6 alkynyl, C 1 -C 6 haloalkyl, C 1 -C 6 alkoxyalkyl, phenyl or benzyl wherein each of the phenyl or the benzyl may be optionally substituted with 1-3 R 10, or with a 5- or 6-membered saturated or unsaturated ring system, or with a 5-6 fused ring system, or with a 6-6 fused ring system each containing 1-3 heteroatoms wherein each ring may be optionally substituted with 1-3 R 10, biphenyl or naphthyl optionally substituted with 1-3 R 10; R 6 is independently halogen, C 1 -C 6 alkyl, C 1 -C 4 haloalkyl, C 1 -C 4 alkoxy, C 1 -C 4 haloalkoxy, C 1 -C4 alkylthio, C 1 -C 4 haloalkylthio, amino, C 1 -C 3 alkylamino, C 2 -C 6 alkoxycarbonyl, C 2 -C 6 alkylcarbonyl, C 2 -C 6 alkylaminocarbonyl, hydroxyl, deuterium, or C 3 -C 6 trialkylsilyl; R 7 is H, C 1 -C 6 alkyl, C 2 -C 6 alkenyl, C 3 -C 6 alkynyl, C 1 -C 6 haloalkyl, C 1 -C 6 alkoxyalkyl, phenyl or benzyl wherein each of the phenyl or the benzyl may be optionally substituted with 1-3 R 10, or with a 5- or 6-membered saturated or unsaturated ring system, or with a 5-6 fused ring system, or with a 6-6 fused ring system each containing 1-3 heteroatoms wherein each ring may be optionally substituted with 1-3 R 10, biphenyl or naphthyl optionally substituted with 1-3 R 10; R 8 is H, C 1 -C 6 alkyl, or C 1 -C 6 haloalkyl; R 9 is phenyl optionally substituted with 1-3 R 10, or a 5- or 6-membered saturated or unsaturated ring containing 1-3 heteroatoms wherein each ring may be optionally substituted with 1-3 R 10; and R 10 is independently halogen, C 1 -C 6 alkyl, C 1 -C 4 haloalkyl, C 1 -C 4 alkoxy, C 1 -C 4 haloalkoxy, C 1 -C 4 alkylthio, C 1 -C 4 haloalkylthio, amino, C 1 -C 6 alkylamino, C 2 -C 6 alkoxycarbonyl, C 2 -C 6 alkylcarbonyl, C 2 -C 6 alkylaminocarbonyl, C 2 -C 6 dialkylamino, hydroxy, cyano, or nitro, or an optical isomer, salt or hydrate thereof. wherein R 1 is: C 1 -C 6 alkyl optionally substituted with 1-3 R 4; -C(=O)R 5; or -CH 2 OC(=O)R 5; C 1 -C 6 alkyl optionally substituted with 1-3 R 4; -C(=O)R 5; or -CH 2 OC(=O)R 5; R 2 is: C 1 -C 6 alkyl optionally substituted with 1-3 R 6; -C(=O)R 7; -C(=O)OR 7; or -(CHR 8) n R 7; wherein n is an integer from 1-3; C 1 -C 6 alkyl optionally substituted with 1-3 R 6; -C(=O)R 7; -C(=O)OR 7; or -(CHR 8) n R 7; wherein n is an integer from 1-3; R 3 is -S 2 R 9; R 4 is independently C 1 -C 6 alkyl, C 1 -C 4 alkoxy, C 1 -C 4 haloalkoxy, C 1 -C 4 alkylthio, C 1 -C 4 haloalkylthio, amino, C 1 -C 3 alkylamino, C 2 -C 6 alkoxycarbonyl, C 2 -C 6 alkylcarbonyl, C 2 -C 6 alkylaminocarbonyl, hydroxyl, deuterium, or C 3 -C 6 trialkylsilyl; R 5 is H, C 1 -C 6 alkyl, C 2 -C 6 alkenyl, C 3 -C 6 alkynyl, C 1 -C 6 haloalkyl, C 1 -C 6 alkoxyalkyl, phenyl or benzyl wherein each of the phenyl or the benzyl may be optionally substituted with 1-3 R 10, or with a 5- or 6-membered saturated or unsaturated ring system, or with a 5-6 fused ring system, or with a 6-6 fused ring system each containing 1-3 heteroatoms wherein each ring may be optionally substituted with 1-3 R 10, biphenyl or naphthyl optionally substituted with 1-3 R 10; R 6 is independently halogen, C 1 -C 6 alkyl, C 1 -C 4 haloalkyl, C 1 -C 4 alkoxy, C 1 -C 4 haloalkoxy, C 1 -C4 alkylthio, C 1 -C 4 haloalkylthio, amino, C 1 -C 3 alkylamino, C 2 -C 6 alkoxycarbonyl, C 2 -C 6 alkylcarbonyl, C 2 -C 6 alkylaminocarbonyl, hydroxyl, deuterium, or C 3 -C 6 trialkylsilyl; R 7 is H, C 1 -C 6 alkyl, C 2 -C 6 alkenyl, C 3 -C 6 alkynyl, C 1 -C 6 haloalkyl, C 1 -C 6 alkoxyalkyl, phenyl or benzyl wherein each of the phenyl or the benzyl may be optionally substituted with 1-3 R 10, or with a 5- or 6-membered saturated or unsaturated ring system, or with a 5-6 fused ring system, or with a 6-6 fused ring system each containing 1-3 heteroatoms wherein each ring may be optionally substituted with 1-3 R 10, biphenyl or naphthyl optionally substituted with 1-3 R 10; R 8 is H, C 1 -C 6 alkyl, or C 1 -C 6 haloalkyl; R 9 is phenyl optionally substituted with 1-3 R 10, or a 5- or 6-membered saturated or unsaturated ring containing 1-3 heteroatoms wherein each ring may be optionally substituted with 1-3 R 10; and R 10 is independently halogen, C 1 -C 6 alkyl, C 1 -C 4 haloalkyl, C 1 -C 4 alkoxy, C 1 -C 4 haloalkoxy, C 1 -C 4 alkylthio, C 1 -C 4 haloalkylthio, amino, C 1 -C 6 alkylamino, C 2 -C 6 alkoxycarbonyl, C 2 -C 6 alkylcarbonyl, C 2 -C 6 alkylaminocarbonyl, C 2 -C 6 dialkylamino, hydroxy, cyano, or nitro,