Boc-2-piperidone (CAS#85908-96-9)
Boc-2-piperidone, chemically designated as tert-butyl 2-oxopiperidine-1-carboxylate or 1-(tert-butoxycarbonyl)-2-piperidone, is an N-protected δ-valerolactam in which the nitrogen atom of the piperidin-2-one ring carries a tert-butoxycarbonyl (Boc) group. It is supplied as a white to cream-colored crystalline powder or fused low-melting solid with a melting point of approximately 32–37 °C and a boiling point of 110 °C at 0.1 mmHg. The compound has a molecular weight of 199.25 g/mol and is soluble in chlorinated and alcoholic solvents such as chloroform and methanol. The N-Boc group is the defining structural feature of the molecule: it protects the lactam nitrogen against undesired nucleophilic or basic attack while simultaneously increasing the lipophilicity and organic solubility of the piperidone scaffold. The compound is air-sensitive and should be stored under an inert atmosphere in a cool, dark place to prevent degradation.
The piperidone ring itself retains an electrophilic carbonyl at the 2-position, enabling elaboration at the α-carbon or the carbonyl carbon prior to deprotection. The Boc group can subsequently be removed under mild acidic conditions (e.g., trifluoroacetic acid in dichloromethane) to unmask the free lactam or piperidine nitrogen, making this intermediate particularly valuable in multi-step sequences where selective functionalization of the ring is required without disturbing the nitrogen center.
Applications
The primary application of Boc-2-piperidone is as a pharmaceutical intermediate for piperidine-based active pharmaceutical ingredients (APIs) . It serves as a key protected lactam building block in medicinal chemistry programs targeting piperidine derivatives with therapeutic potential. A well-documented application is in the synthesis of DPP-4 inhibitors for the treatment of type 2 diabetes; N-Boc-2-piperidone has been used as the starting material for the preparation of novel analogues of alogliptin, where the piperidone core was modified to optimize interactions with the DPP-4 enzyme.
Beyond DPP-4 inhibitors, Boc-2-piperidone is employed in asymmetric synthesis, where it can undergo kinetic resolution via asymmetric deprotonation using chiral bases such as n-BuLi combined with sparteine, enabling access to enantioenriched piperidine derivatives with high selectivity. The compound has also been investigated as a sulfonylation reagent in organic synthesis and drug discovery, and as a protecting group strategy in peptide synthesis and materials science for the selective modification of amino acids and the construction of functionalized polymers. In addition, piperidone-core derivatives bearing the Boc protection have been explored for anticancer activity, with chalcone derivatives containing the piperidone scaffold showing cytotoxicity against colorectal and prostate cancer cell lines through apoptosis induction and NF-κB inhibition.
Preparation Method
Boc-2-piperidone is prepared by N-Boc protection of 2-piperidone. The lactam nitrogen of 2-piperidone is deprotonated under basic conditions (for example with sodium hydride, potassium tert-butoxide, or an appropriate amine base), and the resulting amide anion is treated with di-tert-butyl dicarbonate (Boc₂O) . The Boc anhydride acts as the acylating agent, delivering the tert-butoxycarbonyl group to nitrogen and producing the N-protected lactam together with tert-butanol and carbon dioxide as byproducts. The reaction is typically conducted in an aprotic solvent such as tetrahydrofuran, dichloromethane, or N,N-dimethylformamide at temperatures ranging from 0 °C to ambient, and the product is isolated by aqueous work-up, extraction, and purification by distillation or chromatography.
A related industrial strategy employs Boc-protection from the outset of a multi-step sequence, effectively shielding the lactam nitrogen while the piperidone ring is functionalized at other positions, thereby preventing unwanted side reactions and improving overall selectivity in the construction of piperidine-containing drug scaffolds.
Safety Information
Boc-2-piperidone is generally regarded as not a hazardous substance or mixture under GHS criteria, and it is not classified as hazardous for transportation. One supplier safety data sheet lists H319 (Causes serious eye irritation) with the signal word Warning, and corresponding precautionary statements including P264 (wash skin thoroughly after handling), P280 (wear protective gloves/eye protection), P305+P351+P338 (IF IN EYES: rinse cautiously with water for several minutes; remove contact lenses if present and easy to do), and P337+P313 (if eye irritation persists: get medical advice/attention). The compound may emit irritant fumes during combustion, and firefighters should wear self-contained breathing apparatus.
For safe handling, avoid inhalation of dust and contact with eyes and skin, and use only in areas with appropriate exhaust ventilation. Personal protective equipment including safety goggles, protective gloves, and protective clothing is recommended. In case of eye contact, flush immediately with large amounts of water for at least 15 minutes, separating the eyelids to ensure adequate rinsing, and call a physician promptly. In case of skin contact, rinse thoroughly with large amounts of water and remove contaminated clothing. If inhaled, move to fresh air and give cardiopulmonary resuscitation if breathing is difficult; if ingested, wash out the mouth with water provided the person is conscious and seek medical attention, without inducing vomiting unless directed by medical personnel. Store in a cool, dark place under an inert gas atmosphere, protected from air and moisture, and keep containers tightly closed when not in use. Spills should be absorbed with an inert liquid-binding material (diatomaceous earth, universal binder) and surfaces decontaminated with alcohol, with disposal in accordance with local regulations; the product should be kept away from drains and watercourses.
