A compound of formula I: ** Formula ** where R1 is: H； C1-C6 alkyl optionally substituted with 1-3 R4； C1-C6 alkenyl optionally substituted with 1-3 R4； C3-C6 alkynyl optionally substituted with 1-3 R4； Phenyl or benzyl, in which each phenyl or benzyl can be optionally substituted with 1-3 R5, or with a saturated or unsaturated 5 or 6 membered ring system, or with a condensed 5-6 ring system, or with a system of condensed rings 6-6, each containing 1-3 heteroatoms where each ring may be optionally substituted with 1-3 R5, biphenyl or naphthyl optionally substituted with 1-3 R5； - (CHR6) mOR7； -C (>； = O) R8； -C (>； = S) R8； -C (>； = O) OR8； -C (>； = S) OR8； -S (O) 2R8； - (CHR6) mN (R9) R10； -C (>； = O) N (R9) R10； or -C (>； = S) N (R9) R10； in which m is an integer 1-3； R2 is: H； or C1-C6 alkyl optionally substituted with R4； Alternatively R1 and R2 can be taken together to form>； = CR11N (R12) R13； R3 is -S (O) 2R14； R4 is independently halogen, C1-C6 alkyl, C1-C4 haloalkyl, C1-C4 alkoxy, C1-C4 haloalkoxy, C1-C4-thio alkyl, C1-C4-thio haloalkyl, amino, halotium, alkyl C1-C3-amino, C2-C6-carbonyl alkoxy, C2-C6-carbonyl alkyl, C2-C6-aminocarbonyl alkyl, hydroxyl, or C3-C6-silyl trialkyl； R5 is independently halogen, C1-C6 alkyl, C1-C6 haloalkyl, C1-C6 alkoxy, C1-C6 haloalkoxy, C1-C6-thio alkyl, C1-C6-thio haloalkyl, halotium, amino, alkyl C1-C6-amino, C2-C6-amino dialkyl, C2-C6-carbonyl alkoxy, C1-C6-sulfonyl alkyl or C2-C6-carbonyl alkyl, nitro, hydroxyl, or cyano； R6 is H, C1-C6 alkyl, C1-C6 alkoxy, phenyl or benzyl, where each of the benzyl or phenyl may be optionally substituted with 1-3 R5.Un compuesto de fórmula I: **Fórmula** donde R1 es: H； Alquilo de C1-C6 opcionalmente sustituido con 1-3 R4； Alquenilo de C1-C6 opcionalmente sustituido con 1-3 R4； Alquinilo de C3-C6 opcionalmente sustituido con 1-3 R4； Fenilo o bencilo, en los que cada uno de fenilo o bencilo puede estar opcionalmente sustituido con 1-3 R5, o con un sistema de anillos saturados
