Tricyclazole

Description

log Kow: 1.4. Solubility: In water at 25 C, 1.6 g/L. In acetone 10.4, methanol 25, xylene 2.1 (all in g/l, 25 C). Stability: Stable at 52 C. Relatively stable to ultraviolet light.

Chemical Properties

The prodrug is a off-white solid, not easily decomposed by water and light, and is also heat stable (up to 187°C).

Uses

Tricyclazole is an common active ingredient in several commercial fungicide products used to control rice blast fungus, in transplanted and direct-seeded rice.

Definition

ChEBI: A triazolobenzothiazole that is [1,2,4]triazolo[3,4-b][1,3]benzothiazole which is substituted at position 5 by a methyl group. A fungicide used for the control of rice blast, it is not approved for use within the European Union.

Production Methods

In industrial settings, the synthesis of tricyclazole begins with the preparation of a benzothiazole intermediate, often derived from 2-aminobenzenethiol or similar precursors. This compound undergoes cyclisation and functionalisation steps to introduce the triazole ring, which is essential for its fungicidal activity. The process involves controlled reactions with reagents like formamide or hydrazine derivatives, followed by purification to achieve high technical-grade purity.

Mechanism of action

Systemic, absorbed by roots and foliage and translocated, used mainly as a protectant, inhibits melanin biosynthesis

Metabolism

Animals: Rapid and extensive metabolism.
Plants: The principal metabolite is the hydroxymethyl analog.
Soil/Environment: Kd 4 (loamy sand, pH 6.5, 1.5% o.m.), 45 (loam, pH 5.7, 3.1% o.m.), 21 (clay loam, pH 7.4, 1.9% o.m.), 22 (silty clay loam, pH 5.7, 4.1% o.m.).

Toxicity evaluation

Mammalian toxicology. Oral: Acute oral LD₅₀ for rats 314, mice 245, dogs >50 mg/kg. Skin and eye: Acute percutaneous LD₅₀ for rabbits >2000 mg/kg. Slight eye irritant; nonirritating to skin (rabbits). Inhalation: LC50 (1 h) for rats 0.146 mg/L air. NOEL: (2 yr) for rats 9.6 mg/kg b.w.; for mice 6.7 mg/kg b.w.; (1 yr) for dogs 5 mg/kg b.w.; 3-generation reproduction for rat 3 mg/kg b.w. ADI: 0.03 mg/kg.
Toxicity class: World Health Organization (WHO) (a.i.) II; U.S. Environmental Protection Agency (EPA) (formulation) II RC risk Xn (R22). Ecotoxicology. Birds: Acute oral LD₅₀ for mallard ducks and bobwhite quail >100 mg/kg. Fish: LC50 for bluegill sunfish 16.0, rainbow trout 7.3, goldfish fingerlings 13.5 mg/l. Daphnia: LC50 (48 h) > 20 mg/l; NOEC (21 d) 0.96 mg/L.

Pesticide Type

Fungicide