Isolation Of Amines Research Articles

Tf2O-TMDS combination for the direct reductive transformation of secondary amides to aldimines, aldehydes, and/or amines

The direct partial reduction of highly stable secondary amides to more reactive aldimines and aldehydes is a challenging yet highly demanding transformation. In this context, only three methods have been reported. We report herein an improved version of the Charette’s method. Our protocol consists of activation of secondary amides with triflic anhydride/2-fluoropyridine, and partial reduction of the resulting intermediates with 1,1,3,3-tetramethyldisiloxane (TMDS), which delivered aldimines or aldehydes upon acidic hydrolysis. Aromatic amides were reduced to the corresponding aldimines in 85%–100% NMR yields, and yields (NMR) from aliphatic amides were 72%–86%. Acidic hydrolysis of the aldimine intermediates afforded, in one-pot, the corresponding aldehydes in 80%–96% yields. A simple protocol was established to isolate labile aldimines in pure form in 92%–96% yields. The improved method gave generally higher yields as compared to the known ones, and features the use of cheaper and more atom-economical TMDS as a chemoselective reducing agent. In addition, a convenient extraction protocol has been established to allow the isolation of amines, which constitutes a mild method for the N-deacylation of amides, another highly desirable transformation. The extended method retains the advantages of the original method of Charette in terms of mild conditions, good functional group tolerance, and excellent chemoselectivity.

ChemInform Abstract: Mild N‐Deacylation of Secondary Amides by Alkylation with Organocerium Reagents.

AbstractA new protocol for the deacylation of secondary amides and isolation of amines is reported based on the activation of amides with Tf2O, followed by addition of organocerium reagents, and acidic work‐up.

Mild N-deacylation of secondary amides by alkylation with organocerium reagents

Secondary amides are a class of highly stable compounds serving as versatile starting materials, intermediates and directing groups (amido groups) in organic synthesis. The direct deacylation of secondary amides to release amines is an important transformation in organic synthesis. Here, we report a protocol for the deacylation of secondary amides and isolation of amines. The method is based on the activation of amides with Tf2O, followed by addition of organocerium reagents, and acidic work-up. The reaction proceeded under mild conditions and afforded the corresponding amines, isolated as their hydrochloride salts, in good yields. In combination with the CH activation functionalization methodology, the method is applicable to the functionalization of aniline as well as conversion of carboxylic derivatives to functionalized ketones.

Lipase-catalyzed synthesis of the chiral tetrahydroisoquinoline (R)-salsolinol

An efficient chemoenzymatic route for the synthesis of enantiopure (R)-salsolinol through the use of Candida antarctica lipase A (CALA) was developed. Different parameters, including the acyl agent, the solvent, the temperature, and the amount of enzyme and substrates used, were investigated in order to establish the optimal reaction conditions for the enzymatic kinetic resolution of secondary amines. The combination of CALA with phenyl allyl carbonates in toluene allowed the isolation of amines with high conversion (50%) and ee (98%) values.

Isolation and HPLC determination of amines in wine

The isolation of the amines from wines for liquid chromatography was accomplished by either continuous extraction with Freon 11-methylene chloride or with butanol-methylene chloride. The former method gives high recoveries for high-molecular weight amines and the latter for low molecular weight amines. Amines were dansylated and detected with fluorescence and UV detectors. The methods were used to determine amine contents of wines from different countries. The identification of amines was based on UV spectra of dansylamides with a diode array detector.

Gas-chromatographic separation and identification of aliphatic amines in blood

A method for the separation and identification of aliphatic amines in whole blood has been developed by gas chromatography of their 2,4-dinitrophenyl derivatives. The method described in the present study is based on the isolation of amines from blood, preparation of DNP-amines and their subsequent identification by programmed temperature gas chromatography. Quantitative linearity and reproducibility of the proposed method also suggests the possibility of the determination of amines in blood from various clinical states.