Benzothiazole, or more specifically 1,3-benzothiazole, is an

aromatic In organic chemistry, aromaticity is a chemical property describing the way in which a conjugated system, conjugated ring of unsaturated bonds, lone pairs, or empty orbitals exhibits a stabilization stronger than would be expected from conjugati ...

heterocyclic compound A heterocyclic compound or ring structure is a cyclic compound that has atoms of at least two different elements as members of its ring(s). Heterocyclic organic chemistry is the branch of organic chemistry dealing with the synthesis, proper ...

with the chemical formula . It is colorless, slightly viscous liquid. Although the parent compound, benzothiazole is not widely used, many of its derivatives are found in commercial products or in nature. Firefly luciferin can be considered a derivative of benzothiazole. It has a sulfurous

odor An odor (American English) or odour ( Commonwealth English; see spelling differences) is a smell or a scent caused by one or more volatilized chemical compounds generally found in low concentrations that humans and many animals can perceive ...

and meaty flavor. The three

structural isomers In chemistry, a structural isomer (or constitutional isomer in the IUPAC nomenclature) of a chemical compound, compound is a compound that contains the same number and type of atoms, but with a different connectivity (i.e. arrangement of chemica ...

of benzothizaole are 1,3-benzothiazole, 1,2-benzothiazole and 2,1-benzothiazole.

Structure and reactivity

Benzothiazoles consist of a 5-membered 1,3- thiazole ring fused to a benzene ring. The nine atoms of the bicycle and the attached substituents are coplanar. The heterocyclic core of the molecule is readily substituted at the methyne (CH) centre in the thiazole ring. Thiazole is electron-withdrawing.

Synthesis and biosynthesis

Benzothiazoles are typically prepared by treatment of 2-mercaptoaniline. For example,

acid chloride In organic chemistry, an acyl chloride (or acid chloride) is an organic compound with the functional group . Their formula is usually written , where R is a side chain. They are reactive derivatives of carboxylic acids (). A specific example o ...

s are effective: :C₆H₄(NH₂)SH + RC(O)Cl → C₆H₄(N)SCR + HCl + H₂O Many other precursors have been used, commonly aldehydes in the presence of oxidants. In some cases, benzothiazoles are prepared directly from

aniline Aniline (From , meaning ' indigo shrub', and ''-ine'' indicating a derived substance) is an organic compound with the formula . Consisting of a phenyl group () attached to an amino group (), aniline is the simplest aromatic amine. It is an in ...

s, a process that entails ortho functionalization. Naturally occurring benzothiazoles are proposed to arise by condensation of

cysteine Cysteine (; symbol Cys or C) is a semiessential proteinogenic amino acid with the chemical formula, formula . The thiol side chain in cysteine enables the formation of Disulfide, disulfide bonds, and often participates in enzymatic reactions as ...

with

quinone The quinones are a class of organic compounds that are formally "derived from aromatic compounds benzene.html" ;"title="uch as benzene">uch as benzene or naphthalene] by conversion of an even number of –CH= groups into –C(=O)– groups with ...

Uses

Dyes

The dye thioflavin is a benzothiazole derivative.

Food additives

Benzothiazole occurs naturally in some foods but is also used as a

food additive Food additives are substances added to food to preserve flavor or enhance taste, appearance, or other sensory qualities. Some additives, such as vinegar ( pickling), salt ( salting), smoke ( smoking) and sugar ( crystallization), have been used f ...

. It has a sulfurous

and meaty flavor. The

European Food Safety Authority The European Food Safety Authority (EFSA) is the agency of the European Union (EU) that provides independent scientific advice and communicates on existing and emerging risks associated with the food chain. EFSA was established in February 2002 ...

assessment had "no safety concern at estimated levels of intake as a flavouring substance".

Rubber additive

Accelerators for the

sulfur vulcanization Sulfur vulcanization is a chemical process for converting natural rubber or related polymers into materials of varying hardness, elasticity, and mechanical durability by heating them with sulfur or sulfur-containing compounds. Sulfur forms cros ...

of rubber are based on 2-mercaptobenzothiazoles.

Pharmacology

left, 120px, Ziprasidone is used to treat schizophrenia and bipolar disorder">schizophrenia.html" ;"title="Ziprasidone is used to treat schizophrenia">Ziprasidone is used to treat schizophrenia and bipolar disorder. Benzothiazoles have been widely investigated for their bioactivity. The benzothiazole moiety is, for example, seen in certain dopamine-acting drugs, e.g. riluzole and pramipexole. Moreover, benzothiazole derivatives act as

monoamine oxidase inhibitors Monoamine oxidase inhibitors (MAOIs) are a class of drugs that inhibit the activity of one or both monoamine oxidase enzymes: monoamine oxidase A (MAO-A) and monoamine oxidase B (MAO-B). They are best known as effective antidepressants, espe ...

dopamine antagonists A dopamine antagonist, also known as an anti-dopaminergic and a dopamine receptor antagonist (DRA), is a type of Pharmaceutical drug, drug which blocks dopamine receptors by receptor antagonism. Most antipsychotics are dopamine antagonists, and ...

: * 6-oxoethers and derivatives of thiadiazole, thiazolyhydrazine that act selectively on either

MAO-A Monoamine oxidase A, also known as MAO-A, is an enzyme ( E.C. 1.4.3.4) that in humans is encoded by the ''MAOA'' gene. This gene is one of two neighboring gene family members that encode mitochondrial enzymes which catalyze the oxidative deamin ...

MAO-B Monoamine oxidase B (MAO-B) is an enzyme that in humans is encoded by the ''MAOB'' gene. The protein encoded by this gene belongs to the flavin monoamine oxidase family. It is an enzyme located in the outer mitochondrial membrane. It catalyze ...

depending on the ''O''-sidechain * 1-alkylpiperidines that act on dopamine D₄ receptor

Safety and environmental considerations

Benzothiazoles are widely used in the

vulcanization Vulcanization (British English: vulcanisation) is a range of processes for hardening rubbers. The term originally referred exclusively to the treatment of natural rubber with sulfur, which remains the most common practice. It has also grown to ...

of rubber, so their possible role in the environment has attracted attention. Evidence suggests that they biodegrade readily.

References

External links

MSDS
{{Chemical classes of psychoactive drugs Aromatic bases Simple aromatic rings