13371-12-5Relevant articles and documents
(-)-Menthol as a source of new N,N-diamine ligands for asymmetric transfer hydrogenation
Roszkowski, Piotr,Maurin, Jan K.,Czarnocki, Zbigniew
, p. 2184 - 2188 (2018)
The synthesis of new chiral N-monotosylated-1,2-diamines based on the (-)-menthol skeleton is presented. The elimination of HCl from neomenthyl chloride obtained from an Appel reaction led to p-menth-3-ene in excellent yield. Further functionalization of the double bond in p-menth-3-ene with chloramine-T gave the corresponding N-tosylaziridines, which upon reaction with sodium azide and subsequent reduction of the azide functional group, formed the 1,2-diamine system. The synthesized chiral ligands proved effective in the asymmetric transfer hydrogenation of aromatic ketones and an endocyclic imine.
A mild method for the replacement of a hydroxyl group by halogen: 2. unified procedure and stereochemical studies
Gati, Wafa,Munyemana, Fran?ois,Colens, Alain,Srour, Aladdin,Dufour, Mathilde,Vardhan Reddy, K. Harsha,Téchy, Brigitte,Rosse, Gérard,Schweiger, Ed,Qiao, Qi,Ghosez, Léon
, (2020/08/19)
N,N-Dimethyl- and N,N-diisopropyl-1-halo-2-methyl-l-propenylamines are readily available reagents for the mild deoxyhalogenation of alcohols and hydroxyacids. In this study we showed that the reactivity of the reagents can be tuned by varying the size of the alkyl groups on the reagents: the replacement of methyl by isopropyl groups led to a significant increase of reactivity. We then described a unified procedure for all deoxyhalogenations using the readily available α-chloroenamines as reagents with (bromination, iodination) or without (chlorination) an alkaline bromide or iodide. Finally, we showed that deoxyhalogenation reactions of secondary alcohols were highly stereospecific and generally occurred with inversion of configuration.
Rearrangement in Stereoretentive Syntheses of Menthyl Chloride from Menthol: Insight into Competing Reaction Pathways through Component Quantification Analysis
Hintermann, Lukas,Wong, Kit Ming
supporting information, p. 5527 - 5536 (2017/10/06)
The enantiopure reagent menthyl chloride (2) is generally prepared from (–)-(1R)-menthol (1) with Lucas' reagent (ZnCl2 in conc. aqueous HCl) in a stereoretentive reaction that appeared to be free from accompanying rearrangements. The same was assumed for a recent synthesis of 2 through TiCl4-catalyzed extrusion of SO2 from menthyl chlorosulfite (3). The products of both syntheses have now been analyzed by quantitative 1H and 13C NMR methods, and all reaction components have been identified down to the ≤ 0.5 mol-% level. Either reaction is accompanied by cationic rearrangement to the considerable extent of 18–25 mol-%. Besides the expected 2, neomenthylchloride (4) and five rearrangement products have been identified, among them three regioisomeric tertiary chloromenthanes (9, 10, 11), and both a secondary (12) and tertiary chloride (16) derived from ψ-menthane (1-isobutyl-3-methylcyclopentane). A scheme of rearrangement pathways starting from a common menthyl carbenium ion pair is derived. The effect of purification protocols on crude 2 has been studied quantitatively. Either selective solvolysis of tertiary sideproducts (98 mol-% purity) or low-temperature crystallization (≥ 97 mol-% purity) was successful. An improved, scalable synthesis of 2 through the catalytic rearrangement of chlorosulfite 3 is reported.