Di-tert-butyl dicarbonate

Chemical Properties

Di-tert-butyl dicarbonate (BOC Anhydride, DiBOC) is a colorless to white to yellow crystals, solidified mass or clear liquid. It melts around room temperature (m.p.=23°C). It does not decompose at this or even slightly higher temperatures. For example, it is typically purified by distillation under reduced pressure at temperatures up to around 65°C. At higher temperatures it will decompose to isobutene, t-butyl alcohol and carbon dioxide.

Uses

Di-tert-butyl dicarbonate (Boc2O) is a widely used reagent for introducing protecting groups in peptide synthesis. It plays an important role in the preparation of 6-acetyl-1,2,3,4-tetrahydropyridine by reacting with 2-piperidone. It serves as a protecting group used in solid phase peptide synthesis.

Definition

ChEBI: Di-tert-butyl dicarbonate is an acyclic carboxylic anhydride. It is functionally related to a dicarbonic acid.

Preparation

The preparation of Di-tert-butyl dicarbonate is as follows:To a monoester sodium salt solution were added 2g of N, N-dimethylformamide, 1g of pyridine, 1g of triethylamine,Cooling to -5~0°C, 60g diphosgene was slowly added dropwise within 1.5h dropwise addition was complete, warmed to room temperature (25°C), incubated for 2h, the reaction was allowed to stand after filtration, washing organic solution. Dried with anhydrous magnesium sulfate, the solvent was distilled off at atmospheric pressure to give crude product 65~70g. After cooling and crystallization, 57-60g of di-tert-butyl dicarbonate were obtained in a yield of 60-63%.

Application

Di-tert-butyl dicarbonate has the following uses:
(1) As part of a series of bovine plasma amine oxidase inactivators. Aminomethylenes were prepared by the reaction of Boc propargylamine with formaldehyde, diisopropylamine and copper bromide.
(2) It can be used as a general purpose carboxylation reagent. Carbon nucleophiles generated by a non-nucleophilic base (LDA) were effectively trapped with di-tert-butyl dicarbonate (Boc-anhydride) to provide the corresponding tert-butyl aryl acetates, di-tert-butyl aryl malonates, unsymmetrical aryl malonates and tert-butyl benzoates in high yields.
(3) Alcohols as Boc derivatives were catalytically protected by Lewis acids. Reagents for the introduction of Boc protecting groups.
(4) Reagents for the preparation of Boc-protected amines. Tri-tert-butoxycarbonyl-protected hydrazines prepare Fmoc esters in chromogenic reagents for monitoring solid-phase aldehydes.

Reactions

The reaction of substituted anilines with Boc2O in the presence of a stoichiometric amount of 4-dimethylaminopyridine (DMAP) in an inert solvent (acetonitrile, dichloromethane, ethyl acetate, tetrahydrofuran, toluene) at room temperature leads to aryl isocyanates in almost quantitative yields within 10 min.
Di-tert-butyl dicarbonate and 4-(dimethylamino)pyridine revisited. Their reactions with amines and alcohols

General Description

Di-tert-butyl dicarbonate (Boc₂O) is a reagent mainly used for the introduction of the Boc protecting group to amine functionalities. It is also used as a dehydrating agent in some organic reactions, particularly with carboxylic acids, certain hydroxyl groups, or with primary nitroalkanes.

Hazard

An irritant that may cause serious eye injury; May cause skin sensitization; Highly toxic by inhalation

Flammability and Explosibility

Flammable

reaction suitability

reaction type: Coupling Reactions

Purification Methods

Melt the ester by heating at ~35o, and distil it in a vacuum. If IR and NMR ( 1810m 1765 cm-1 , in CCl4 1.50 singlet) suggest very max impure, then wash with an equal volume of H2O containing citric acid to make the aqueous layer slightly acidic, collect the organic layer and dry it over anhydrous MgSO4 and distil it in a vacuum. [Pope et al. Org Synth 57 45 1977, Keller et al. Org Synth 63 160 1985, Grehn et al. Angew Chem 97 519 1985.] FLAMMABLE.