Tetrahydroisoquinoline (TIQ or THIQ) is an

organic compound In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known. T ...

with the chemical formula C₉H₁₁N. Classified as a

secondary amine In chemistry, amines (, ) are compounds and functional groups that contain a basic nitrogen atom with a lone pair. Amines are formally derivatives of ammonia (), wherein one or more hydrogen atoms have been replaced by a substituent such ...

, it is derived from

isoquinoline Isoquinoline is a heterocyclic aromatic organic compound. It is a structural isomer of quinoline. Isoquinoline and quinoline are benzopyridines, which are composed of a benzene ring fused to a pyridine ring. In a broader sense, the term isoqu ...

by hydrogenation. It is a colorless viscous liquid that is miscible with most organic solvents. The tetrahydroisoquinoline skeleton is encountered in a number of bioactive compounds and drugs.

Reactions

As a secondary amine, tetrahydroisoquinoline has weakly basic properties and forms salts with strong acids. It can be dehydrogenated to give isoquinoline and hydrogenated to decahydroisoquinoline. Like other secondary amines, tetrahydroisoquinoline can be oxidized to the corresponding nitrone using

hydrogen peroxide Hydrogen peroxide is a chemical compound with the formula . In its pure form, it is a very pale blue liquid that is slightly more viscous than water. It is used as an oxidizer, bleaching agent, and antiseptic, usually as a dilute solution (3%� ...

, catalyzed by

selenium dioxide Selenium dioxide is the chemical compound with the formula SeO2. This colorless solid is one of the most frequently encountered compounds of selenium. Properties Solid SeO2 is a one-dimensional polymer, the chain consisting of alternating seleniu ...

Toxicology

Tetrahydroisoquinoline derivatives may be formed in the body as metabolites of some drugs, and this was once thought to be involved in the development of

alcoholism Alcoholism is, broadly, any drinking of alcohol that results in significant mental or physical health problems. Because there is disagreement on the definition of the word ''alcoholism'', it is not a recognized diagnostic entity. Predomi ...

. This theory has now been discredited and is no longer generally accepted by the scientific community, but endogenous production of neurotoxic tetrahydroisoquinoline derivatives such as

norsalsolinol Norsalsolinol is a chemical compound that is produced naturally in the body through metabolism of dopamine. It has been shown to be a selective dopaminergic neurotoxin, and has been suggested as a possible cause of neurodegenerative conditions suc ...

continue to be investigated as possible causes for some conditions such as

Parkinson's disease Parkinson's disease (PD), or simply Parkinson's, is a long-term degenerative disorder of the central nervous system that mainly affects the motor system. The symptoms usually emerge slowly, and as the disease worsens, non-motor symptoms becom ...

Tetrahydroisoquinolines

The tetrahydroisoquinoline skeleton is present in a number of drugs, such as

tubocurarine Tubocurarine (also known as ''d''-tubocurarine or DTC) is a toxic alkaloid historically known for its use as an arrow poison. In the mid-1900s, it was used in conjunction with an anesthetic to provide skeletal muscle relaxation during surgery or ...

, one of the

quaternary ammonium muscle relaxants Neuromuscular-blocking drugs block neuromuscular transmission at the neuromuscular junction, causing paralysis of the affected skeletal muscles. This is accomplished via their action on the post-synaptic acetylcholine (Nm) receptors. In clin ...

. Drugs based on 4-substituted tetrahydroisoquinolines include

nomifensine Nomifensine (Merital, Alival) is a norepinephrine-dopamine reuptake inhibitor, i.e. a drug that increases the amount of synaptic norepinephrine and dopamine available to receptors by blocking the dopamine and norepinephrine reuptake transporters ...

and

diclofensine Diclofensine (Ro 8-4650) was developed by Hoffmann-La Roche in the 1970s in the search for a new antidepressant. It was found that the (''S'')-isomer was responsible for activity. Is a stimulant drug which acts as a Serotonin-noradrenaline-dopami ...

. They can be prepared by ''N''-alkylation of benzyl amines with halo

acetophenone Acetophenone is the organic compound with the chemical formula, formula C6H5C(O)CH3. It is the simplest aromatic ketone. This colorless, viscous liquid is a precursor to useful resins and fragrances. Production Acetophenone is formed as a byprodu ...

s. Naturally occurring tetrahydroisoquinolines include cheryllinecherylline
/ref> and latifine. Esproquin, which shows hypotensive activity by virtue of its α-adrenergic blocking properties, is made from THIQ.

References

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