Asymmetric catalysis in fragrance chemistry: a new synthetic approach to enantiopure Phenoxanol®, Citralis® and Citralis Nitrile®
摘要:
A new approach to the synthesis of the single stereomers of the fragrances Phenoxanol (R), Citralis (R) and Citralis Nitrile (R) is reported. The key step of the synthesis is the asymmetric hydrogenation of (Z)- or (E)-3-methyl-5-phenyl-pent-2-en-1-ol, which leads to the single enantiomers of Phenoxanol (R) from which both enantiomers of Citralis (R) are obtained by oxidation. Treatment of these compounds with hydroxylamine finally led to Citralis Nitrile (R) without any loss of enantiopurity. The odour profiles of the single enantiomers of these fragrances are reported as well. (c) 2007 Elsevier Ltd. All rights reserved.
Iron-Catalyzed Tunable and Site-Selective Olefin Transposition
作者:Xiaolong Yu、Haonan Zhao、Ping Li、Ming Joo Koh
DOI:10.1021/jacs.0c08631
日期:2020.10.21
earth-abundant iron-based complex, a base and a boryl compound promote efficient and controllable alkene transposition. Mechanistic investigations reveal that these processes likely involve in situ formation of an iron-hydride species which promotes olefin isomerization through sequential olefin insertion/β-hydride elimination. Through this strategy, regiodivergent access to different products from
CC 双键的催化异构化是必不可少的化学转化,用于提供更高价值的类似物,在化学工业中具有重要用途。尽管在该领域取得了进展,但仍然迫切需要一种通用催化解决方案,能够精确控制环状和非环状体系中的 C=C 键迁移位置,以提供二取代和三取代烯烃。在这里,我们展示了催化量的合适的地球丰富的铁基络合物、碱和硼基化合物促进有效和可控的烯烃转位。机理研究表明,这些过程可能涉及原位形成铁氢化物物种,该物种通过顺序烯烃插入/β-氢化物消除促进烯烃异构化。通过这个策略,
Chemoselective Biohydrogenation of Alkenes in the Presence of Alkynes for the Homologation of 2‐Alkynals/3‐Alkyn‐2‐ones into 4‐Alkynals/Alkynols
作者:Danilo Colombo、Elisabetta Brenna、Francesco G. Gatti、Maria Chiara Ghezzi、Daniela Monti、Fabio Parmeggiani、Francesca Tentori
DOI:10.1002/adsc.201900177
日期:——
activated alkene bonds by ene‐reductases (ERs) is completely chemoselective, because of the mechanism of the reaction. Thus, we investigated the use of ERs belonging to the Old Yellow Enzyme family for the reduction of α,β‐unsaturated aldehydes with a conjugated C≡C triple bond at the γ position. This reaction was exploited as the key step for the development of an effective homologation route to convert
copper-catalyzed coupling reaction of 2-pyridinesulfonates with Grignardreagents revealed that reactions with catalytic Cu(OTf)2 were completed in <40 min. The results differed from those of the previous CuI-catalyzed reactions of tosylates in the presence of additives (LiOMe and TMEDA) for 12–24 h. It was shown that the preferred coordination of the leaving group to the reagents accelerated the reaction
Asymmetric conjugate addition of alkylzirconium reagents to α,β-unsaturated thioesters: access to fragrances and acyclic stereochemical arrays
作者:Zhenbo Gao、Stephen P. Fletcher
DOI:10.1039/c7cc05433e
日期:——
Copper-catalyzed asymmetric conjugateaddition of alkylzirconium species to α,β-unsaturated thioesters is reported. A variety of functioanlized alkyl nucleophiles were introduced with yields around 70% and ee’s over 92%. The method was applied to the straightforward syntheses of the commercially important fragrances phenoxanol (both enantiomers 97% ee), and hydroxycitronellal (98% ee). The 1,4-addition