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.
Remote sp3 C–H Amination of Alkenes with Nitroarenes
作者:Jichao Xiao、Yuli He、Feng Ye、Shaolin Zhu
DOI:10.1016/j.chempr.2018.04.008
日期:2018.7
Direct installation of a functional group at remote, unfunctionalized sites in an alkyl chain is a synthetically valuable but rarely reported process. The remote relay hydroarylamination of distal and proximal olefins, and of olefin isomeric mixtures, has been achieved through NiH-catalyzed alkene isomerization and sequential reductive hydroarylamination with nitroarenes. This provides an attractive
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
Cobalt‐Catalyzed Asymmetric 1,4‐Reduction of
<i>β,β‐</i>
Dialkyl
<i>α</i>
,
<i>β</i>
‐Unsaturated Esters with PMHS
作者:Dongpo Lu、Peng Lu、Zhan Lu
DOI:10.1002/ejoc.202100856
日期:2021.9.14
A cobalt-catalyzed asymmetric reduction of β,β-dialkyl α,β-unsaturatedesters with polymethylhydrosiloxane (PMHS) was reported to deliver the corresponding esters containing a chiral trialkyl carbon center at β-position with up to 97 % yield and 98 % ee. The chiral tridentate ligand oxazoline iminopyridine (OIP) could perform well for the asymmetric reduction instead of chiral bidentate ligands. This
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
Asymmetric Hydrogenation of Allylic Alcohols Using Ir–N,P-Complexes
作者:Jia-Qi Li、Jianguo Liu、Suppachai Krajangsri、Napasawan Chumnanvej、Thishana Singh、Pher G. Andersson
DOI:10.1021/acscatal.6b02456
日期:2016.12.2
γ-disubstituted and β,γ-disubstituted allylicalcohols were prepared and successfully hydrogenated using suitable N,P-based Ir complexes. High yields and excellent enantioselectivities were obtained for most of the substrates studied. This investigation also revealed the effect of the acidity of the N,P–Ir-complexes on the acid-sensitive allylicalcohols. DFT ΔpKa calculations were used to explain the effect of