Tert-butanesulfinamide Research Articles

Novel enantioselective synthesis of (S)-ketamine using chiral auxiliary and precursor Mannich base

Ketamine has been extensively used as an anesthetic drug. Chiral auxiliaries such as tert-butanesulfinamide (TBSA) can be used for the asymmetric synthesis of (S)-ketamine. Condensation of TBSA with ketones provides tert-butanesulfinylimines in consistently high yields. The tert-butanesulfinyl group actuates the imine for nucleophilic addition, is a potent chiral directing group, and after nucleophilic addition is easily dissociated by intervention with acid solution. To prepare 2-(N-piperidinomethyl)-1-phenylcyclohexylamine (1), we started with the cyclohexanone and using Mannich reaction achieved an aminoketone. Then, we made the sulfiniylamin (2) by the condensation of TBSA with aminoketone. By using salts such as Ti(OEt)4, we obtained N-tert-butanesulfinylketimine in 85% yield. Next, we provided a new chiral center (3) using Grignard reagent as nucleophile at −78 °C (80% yield). Finally, after many steps, the (S)-ketamine synthesized under ozonolysis conditions, with good yield and enantioselectivity (75% yield and 75% ee).

Development of a Large-Scale Asymmetric Process for tert-Butanesulfinamide

Process development for a scalable and green synthesis of chiral tert-butanesulfinamide (TBSA) on a multikilogram scale is reported. The process is based on the identification of a chiral sulfinyl transfer agent, benzo[1,3]oxathiozin-2-one, that contains active and differentiated S–N and S–O bonds, allowing the synthesis to proceed under mild reaction conditions. This method is practical and overcomes the disadvantages of earlier methods deploying harsh reaction conditions and hazardous and toxic reagents.

A novel strategy for the asymmetric synthesis of (S)-ketamine using (S)-tert-butanesulfinamide and 1,2-cyclohexanedione

We present a novel asymmetric synthesis route for synthesis of (S)-ketamine using a chiral reagent according to the strategy (Scheme 1), with good enantioselectivity (85% ee) and yield. In this procedure, the (S)-tert-butanesulfinamide (TBSA) acts as a chiral auxiliary reagent to generate (S)-ketamine. A series of new intermediates were synthesized and identified for the first time in this work (2–4). The monoketal intermediate (1) easily obtained after partial conversion of one ketone functional group of 1,2-cyclohexanedione into a ketal using ethylene glycol. The sulfinylimine (2) was obtained by condensation of (S)-tert-butanesulfinamide (TBSA) with (1), 4-dioxaspiro[4.5]decan-6-one in 90% yield. The (S)-N-tert-butanesulfinyl ketamine (3) was prepared on further reaction of sulfinylimine (2) with appropriate Grignard reagent (ArMgBr) in which generated chiral center in 85% yield and with 85% diastereoselectivity. Methylation of amine afforded the product (4). Finally, the sulfinyl- and ketal-protecting groups were removed from the compound (4) by brief treatment with stoichiometric quantities of HCl in a protic solvent gave the (S)-ketamine in near quantitative yield.

ChemInform Abstract: Zinc Radical Transfer Based Modular Approach to Enantiopure Alkylidene‐β‐prolines from N‐(tert‐Butylsulfinyl)‐α‐(aminomethyl)acrylates.

AbstractA modular entry to enantiopure (E)‐2‐substituted 3‐alkylideneprolines is disclosed in 5 or 6 steps from tert‐butanesulfinamide.