Correction: Highly selective aluminium-catalysed intramolecular Prins reaction for <scp>l</scp>-menthol synthesis

Itoh, Hisanori; Maeda, Hironori; Yamada, S.; Hori, Yoji; Mino, Takashi; Sakamoto, Masami

doi:10.1039/c5ra90068a

“…Diastereoselective cyclization of (+)‐citronellal, catalysed by homogeneous aluminium complexes, was explored by Itoh et al from the company Takasago 91,92 . They reported an excellent diastereoselectivity for (−)‐isopulegol of 99.5%, with an overall yield of 95% with the 2‐cyclohexyl‐6‐phenylphenol ligand on a 100 g scale 91 . After hydrogenation with Raney‐Nickel, (−)‐menthol was obtained with 91% yield and 99.5% diastereomeric purity.…”

Section: Synthesis Routes Including Citronellalmentioning

confidence: 99%

Synthesis of (−)‐menthol: Industrial synthesis routes and recent development

Dylong

¹

,

Hausoul

²

,

Palkovits

³

et al. 2022

Flavour & Fragrance J

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Abstract(−)‐Menthol is one of the most popular aroma compounds worldwide. While in the past mostly extracted from mint plants, today (−)‐menthol synthesis from other raw materials is becoming more relevant. Common starting materials for menthol synthesis are m‐cresol, citral and myrcene, but also substrates like menthone, mono‐ and bicyclic terpenes and terpenoids have been used for this purpose in the past. As for many applications (−)‐menthol of high purity is required, asymmetric syntheses and enantiomeric resolution of obtained raw products are applied for menthol production. This review gives an overview on the most important synthetic menthol production processes of the companies Symrise, Takasago and BASF and relevant literature in the field of menthol synthesis with a focus on the last 20 years.

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“…The commercial processes were reported using non-environmentally friendly catalysts such as ZnBr 2 , BF 3 , SbCl 3 , TiCl 4 , etc with about 70% of yield [8,9]. The transformation of citronellal to isopulegol was also reported using SiO 2 , TiO 2 , ZrO 2 , FeF 3 -MgF 2 , 1.5%Pd-20%PW/SiO 2 , etc in organic solvents [8,10]. These processes gave up to 90% yield with inferior selectivity of key isomer (isopulegol) at high temperature (up to 250 o C), and H 2 pressure (5-50 bar).…”

Section: Introductionmentioning

confidence: 99%

Exploitation of Liquid CO2 Based Greener Process for Valorization of Citronellal-Rich Essential Oils Into Flavor Grade (−)-Menthol Using Novel Sn/Al-B-NaYZE Composites

Kumar

¹

,

Chanotiya

²

,

Bawitlung

³

et al. 2022

Waste Biomass Valor

2

0

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A two-step greener catalytic process has been developed for semi-synthesis of (-)-menthol from citronellal-rich essential oils such as Cymbopogon winterianus and Corymbia citriodora by using novel bi-acidic composites. These novel composites (Al-B-NaYZE or Sn-B-NaYZE) were prepared by impregnation of Sn-B and Al-B over NaYZE framework to increase the Lewis and Bronsted acidic sites. These composites were thoroughly characterized using TDP, FT-IR, UV, XRD, SEM, HRTEM, SA, and TGA. The composite Sn-B-NaYZE cyclized 99% of citronellal to isopulegol isomers with 99% selectivity in 45 min under liquid CO 2 medium, while composite Al-B-NaYZE is showing 95% selectivity towards isopulegol isomers. Sn-B-NaYZE was displayed ehnaced selectivity due to its higher acidic property as con rmed by the TPD analysis. The chiral study indicates that the Sn-B-NaYZE composite is giving highest selectivity (94%) towards (-)-isopulegol. (+)-Citronellal or citronellal oil was found as an ideal substate for (-)-menthol production. It observed that Sn-B molar ratio over base material NaY-Zeolite was played a mojor role for catalytic activity and selectivity towards (-)-isopulegol.Further, isopulegol isomers were reduced to 98% of menthol using 1%Pd/AC at 40 psi H 2 pressure in 1 h.Reaction mixture slowly frozen to -40 o C for trouble-free isolation of the crude menthol. Further, pharmaceutical and avor grade (-)-menthol was puri ed from the crude menthol through esteri cation process. This (-)menthol was found to 100% biobased on 14 C-radiocarbon-dating to authenticate as nature-identical. The composite has displayed high reusability up to ve times without signi cant loss in their activity. After isolation of menthol, the spent oil was enrich with oxygenated monoterpenoids, hence it was displayed signi cant antimicrobial activities. Statement Of NoveltyA two-step greener catalytic process has been developed for semi-synthesis of (-)-menthol from citronellal-rich essential oils using novel bi-acidic composites. The composite Sn-B-NaYZE cyclized 99% of citronellal to isopulegol isomers with 99% selectivity in 45 min under liquid CO 2 medium, while composite Al-B-NaYZE is showing 95% selectivity towards isopulegol isomers and this is due to higher acidic property of Sn-B-NaYZE.The chiral study indicates that the Sn-B-NaYZE composite is giving highest selectivity (94%) towards (-)isopulegol. Sn-B molar ratio over base material NaY-Zeolite have displayed a signi cant catalytic activity and selectivity towards (-)-isopulegol. This isopulegol isomers were reduced to 98% of menthol using 1%Pd/AC at 40 psi H 2 pressure in 1 h. Further, pharmaceutical and avor grade (-)-menthol was puri ed and this (-)-menthol was found to 100% biobased on 14 C-radiocarbon-dating to authenticate as nature-identical. After isolation of menthol, the spent oil was enrich with oxygenated monoterpenoids, hence it was displayed signi cant antimicrobial activities. The present study provides the eco-friendly greener process for direct valorization of citronellal rich esse...

show abstract

Exploitation of liquid CO2 based greener process for valorization of citronellal rich essential oils into flavor grade (-)-menthol using novel Sn/Al-B-NaYZE composites

Kumar

¹

,

Chanotiya

²

,

Bawitlung

³

et al. 2022

Preprint

0

View full text Add to dashboard Cite

A two-step greener catalytic process has been developed for semi-synthesis of (-)-menthol from citronellal-rich essential oils such as Cymbopogon winterianus and Corymbia citriodora by using novel bi-acidic composites. These novel composites (Al-B-NaYZE or Sn-B-NaYZE) were prepared by impregnation of Sn-B and Al-B over NaYZE framework to increase the Lewis and Bronsted acidic sites. These composites were thoroughly characterized using TDP, FT-IR, UV, XRD, SEM, HRTEM, SA, and TGA. The composite Sn-B-NaYZE cyclized 99% of citronellal to isopulegol isomers with 99% selectivity in 45 min under liquid CO2 medium, while composite Al-B-NaYZE is showing 95% selectivity towards isopulegol isomers. Sn-B-NaYZE was displayed ehnaced selectivity due to its higher acidic property as confirmed by the TPD analysis. The chiral study indicates that the Sn-B-NaYZE composite is giving highest selectivity (94%) towards (-)-isopulegol. (+)-Citronellal or citronellal oil was found as an ideal substate for (-)-menthol production. It observed that Sn-B molar ratio over base material NaY-Zeolite was played a mojor role for catalytic activity and selectivity towards (-)-isopulegol. Further, isopulegol isomers were reduced to 98% of menthol using 1%Pd/AC at 40 psi H2 pressure in 1 h. Reaction mixture slowly frozen to -40oC for trouble-free isolation of the crude menthol. Further, pharmaceutical and flavor grade (-)-menthol was purified from the crude menthol through esterification process. This (-)-menthol was found to 100% biobased on 14C-radiocarbon-dating to authenticate as nature-identical. The composite has displayed high reusability up to five times without significant loss in their activity. After isolation of menthol, the spent oil was enrich with oxygenated monoterpenoids, hence it was displayed significant antimicrobial activities.

show abstract

Correction: Highly selective aluminium-catalysed intramolecular Prins reaction for l-menthol synthesis

Abstract: Correction for ‘Highly selective aluminium-catalysed intramolecular Prins reaction for l-menthol synthesis’ by H. Itoh et al., RSC Adv., 2014, 4, 61619–61623.

Cited by 3 publications

References 0 publications

Synthesis of (−)‐menthol: Industrial synthesis routes and recent development

Synthesis of (−)‐menthol: Industrial synthesis routes and recent development

Exploitation of Liquid CO2 Based Greener Process for Valorization of Citronellal-Rich Essential Oils Into Flavor Grade (−)-Menthol Using Novel Sn/Al-B-NaYZE Composites

Exploitation of liquid CO2 based greener process for valorization of citronellal rich essential oils into flavor grade (-)-menthol using novel Sn/Al-B-NaYZE composites

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