26510-92-9Relevant articles and documents
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.
A General Route to Enantiomerically Pure Sulfoxides from a Chiral Sulfite
Rebiere, F.,Samuel, O.,Ricard, L.,Kagan, H.B.
, p. 5991 - 5999 (2007/10/02)
Enantiomerically pure cyclic chiral sulfite (S)-7 (trans stereochemistry) has been easily obtained in two steps from (S)-ethyl lactate.This compound was found to react cleanly with many organometallics to give crystalline sulfinates with high regioselecti
