1-Benzyl-4-hydroxypiperidine: Properties, Synthesis & Applications

1-Benzyl-4-hydroxypiperidine is a bifunctionally substituted piperidine derivative widely employed as a versatile synthetic building block in medicinal chemistry and pharmaceutical research.

CAS Number

4727-72-4

Molecular Formula

C₁₂H₁₇NO

Molecular Weight

191.27 g/mol

Key Functional Groups

Tertiary amine (N-benzyl), secondary alcohol (4-OH)

Appearance

White to off-white crystalline solid

Primary Use

Pharmaceutical intermediate and medicinal chemistry scaffold

Chemical Identity and Physical Properties

1-Benzyl-4-hydroxypiperidine (CAS 4727-72-4) is a six-membered nitrogen-containing heterocycle bearing two key functional handles: an N-benzyl group at the ring nitrogen and a hydroxyl group at the 4-position of the piperidine ring. Its molecular formula is C₁₂H₁₇NO with a molecular weight of approximately 191.27 g/mol.

The compound typically presents as a white to off-white crystalline solid at room temperature. The tertiary amine nitrogen confers moderate basicity, while the secondary alcohol at C-4 provides a site for further functionalization via esterification, etherification, oxidation to the corresponding ketone, or conversion to a leaving group for nucleophilic substitution reactions. These dual reactive sites make it a highly attractive starting material and intermediate in complex molecule synthesis.

Storage is recommended in a cool, dry, well-ventilated location, away from incompatible oxidizing agents, in a tightly sealed container to prevent moisture uptake and maintain reagent integrity over time.

Synthetic Utility and Reaction Chemistry

The 4-hydroxyl group of 1-Benzyl-4-hydroxypiperidine can undergo a broad range of transformations that are central to modern synthetic chemistry. Oxidation with reagents such as Swern conditions, Dess-Martin periodinane, or TEMPO-based protocols converts the alcohol to 1-benzyl-4-piperidone, itself a prolific scaffold in drug discovery. Conversely, the hydroxyl can be activated as a mesylate or tosylate to introduce diverse nucleophiles in SN2 reactions, enabling C–O, C–N, and C–S bond formation.

O-Alkylation and O-acylation reactions readily furnish ether and ester derivatives, expanding the structural diversity accessible from this single precursor. The N-benzyl protecting group is orthogonally removable by hydrogenolysis under palladium catalysis (Pd/C, H₂ or ammonium formate transfer hydrogenation), unmasking the free secondary amine (4-hydroxypiperidine) for subsequent elaboration. This deprotection strategy is a cornerstone of multi-step synthetic routes targeting piperidine-containing APIs.

Additionally, Mitsunobu reactions at the 4-OH position allow stereochemical inversion with retention of overall connectivity, providing access to both epimers of 4-substituted piperidine targets—a feature particularly valuable in stereostructure–activity relationship (SAR) studies.

Applications in Medicinal Chemistry and Drug Discovery

The piperidine ring system is among the most prevalent nitrogen-containing heterocycles found in FDA-approved small-molecule drugs, and 1-Benzyl-4-hydroxypiperidine serves as a direct entry point into this privileged structural class. Its dual functionality allows medicinal chemists to construct libraries of analogues with systematic variation at both the nitrogen and the 4-position oxygen, facilitating rapid SAR exploration.

This building block is commonly employed in the preparation of CNS-active compounds, where the piperidine scaffold contributes to favorable pharmacokinetic profiles including blood-brain barrier permeability. It also features as an intermediate in the synthesis of various receptor ligands, enzyme inhibitors, and prodrug platforms where controlled release from the 4-OH ester linkage is exploited.

In fragment-based drug discovery (FBDD) and high-throughput synthesis workflows, 1-Benzyl-4-hydroxypiperidine's commercial availability, defined stereoelectronic properties, and broad synthetic versatility make it a frequent component of compound libraries screened against diverse therapeutic targets, including GPCRs, ion channels, and kinases.

Handling, Safety, and Storage Recommendations

As with most synthetic organic intermediates, standard laboratory precautions apply when working with 1-Benzyl-4-hydroxypiperidine. Personal protective equipment (PPE) including nitrile gloves, a laboratory coat, and safety goggles should be worn at all times. Work should be conducted in a well-ventilated fume hood to minimize inhalation exposure to dust or aerosols generated during weighing or transfer operations.

The compound should be stored in a tightly closed container in a cool, dry environment, away from heat sources, open flames, and incompatible materials such as strong oxidizing agents. Researchers should consult the current Safety Data Sheet (SDS) provided by Aladdin Scientific prior to use for comprehensive hazard, first-aid, and disposal information specific to this reagent.

Waste containing this compound should be disposed of in accordance with local, institutional, and national regulations governing chemical waste. Contaminated containers should not be reused and should be disposed of as chemical waste.

Frequently asked questions

What is 1-Benzyl-4-hydroxypiperidine primarily used for in research?

It is primarily used as a bifunctional synthetic building block in medicinal chemistry and pharmaceutical research. The secondary 4-hydroxyl group and the N-benzyl moiety each provide independent sites for chemical elaboration, enabling the construction of diverse piperidine-containing analogues for SAR studies and drug candidate synthesis.

How can the N-benzyl group of 1-Benzyl-4-hydroxypiperidine be removed?

The N-benzyl protecting group can be cleanly removed by catalytic hydrogenolysis using palladium on carbon (Pd/C) under hydrogen gas, or by transfer hydrogenation using a hydrogen donor such as ammonium formate. This orthogonal deprotection reveals the free 4-hydroxypiperidine nitrogen for further synthetic transformations.

What are the recommended storage conditions for 1-Benzyl-4-hydroxypiperidine?

The compound should be stored in a tightly sealed container under cool, dry conditions, away from direct sunlight, heat sources, and incompatible oxidizing agents. Always consult the current Safety Data Sheet (SDS) from Aladdin Scientific for the most specific and up-to-date storage guidance.

Can 1-Benzyl-4-hydroxypiperidine be oxidized to the corresponding ketone?

Yes. The 4-hydroxyl group can be selectively oxidized to give 1-benzyl-4-piperidone using standard alcohol oxidation protocols such as Swern oxidation, Dess-Martin periodinane, or TEMPO/oxidant systems. 1-Benzyl-4-piperidone is itself a widely used scaffold in drug discovery and heterocyclic chemistry.

References

1. Carey, F. A.; Sundberg, R. J. Advanced Organic Chemistry, Part B: Reactions and Synthesis, 5th ed.; Springer: New York, 2007.
2. Küenburg, B.; Czollner, L.; Bruckmayer, F.; Jordis, U. Development of a Pilot-Scale Synthesis of the Anti-Alzheimer Drug (–)-Galanthamine Using Large-Scale Phenolic Oxidative Coupling and Tiemann Rearrangement as Key Steps. Org. Lett. 1999, 1(13), 1857–1859. doi:10.1021/ol9908793
3. Vitaku, E.; Smith, D. T.; Njardarson, J. T. Analysis of the Structural Diversity, Substitution Patterns, and Frequency of Nitrogen Heterocycles among U.S. FDA Approved Pharmaceuticals. J. Med. Chem. 2014, 57(24), 10257–10274. doi:10.1021/jm501100b
4. Mitsunobu, O. The Use of Diethyl Azodicarboxylate and Triphenylphosphine in Synthesis and Transformation of Natural Products. Synthesis 1981, 1, 1–28. doi:10.1055/s-1981-29317

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