29414-55-9Relevant articles and documents
A Dinickel Catalyzed Cyclopropanation without the Formation of a Metal Carbene Intermediate
Maity, Arnab K.,Kalb, Annah E.,Zeller, Matthias,Uyeda, Christopher
supporting information, p. 1897 - 1902 (2020/11/30)
(NDI)Ni2 catalysts (NDI=naphthyridine-diimine) promote cyclopropanation reactions of 1,3-dienes using (Me3Si)CHN2. Mechanistic studies reveal that a metal carbene intermediate is not part of the catalytic cycle. The (NDI)Ni2(CHSiMe3) complex was independently synthesized and found to be unreactive toward dienes. Based on DFT models, we propose an alternative mechanism that begins with a Ni2-mediated coupling of (Me3Si)CHN2 and the diene. N2 extrusion followed by radical C?C bond formation generates the cyclopropane product. This model reproduces the experimentally observed regioselectivity and diastereoselectivity of the reaction.
Organocatalytic epoxidation and allylic oxidation of alkenes by molecular oxygen
Orfanidou, Maria,Petsi, Marina,Zografos, Alexandros L.
supporting information, p. 9172 - 9178 (2021/11/30)
Pyrrole-proline diketopiperazine (DKP) acts as an efficient mediator for the reduction of dioxygen by Hantzsch ester under mild conditions to allow the aerobic metal-free epoxidation of electron-rich alkenes. Mechanistic crossovers are underlined, explaining the dual role of Hantzsch ester as a reductant/promoter of the DKP catalyst and a simultaneous competitor for the epoxidation of alkenes when HFIP is used as a solvent. Expansion of this protocol to the synthesis of allylic alcohols was achieved by adding a catalytic amount of selenium dioxide as an additive, revealing a superior method to the classical application of t-BuOOH as a selenium dioxide oxidant.
Sustainable catalytic epoxidation of biorenewable terpene feedstocks using H2O2as an oxidant in flow microreactors
Bull, Steven D.,Cunningham, William B.,Plucinski, Pawel,Tibbetts, Joshua D.,Vezzoli, Massimiliano
supporting information, p. 5449 - 5455 (2021/08/16)
Solvent-free continuous flow epoxidation of the alkene bonds of a range of biorenewable terpene substrates have been carried out using a recyclable tungsten-based polyoxometalate phase transfer catalyst and aqueous H2O2 as a benign oxidant. These sustainable flow epoxidation reactions are carried out in commercial microreactors containing static mixing channels that enable common monoterpenes (e.g. untreated crude sulfate turpentine, limonene, etc.) to be safely epoxidized in short reaction times and in good yields. These flow procedures are applicable for the flow epoxidation of trisubstituted and disubstituted alkenes for the safe production of multigram quantities of a wide range of epoxides. This journal is
Sustainable catalytic protocols for the solvent free epoxidation and: Anti -dihydroxylation of the alkene bonds of biorenewable terpene feedstocks using H2O2 as oxidant
Cunningham, William B.,Tibbetts, Joshua D.,Hutchby, Marc,Maltby, Katarzyna A.,Davidson, Matthew G.,Hintermair, Ulrich,Plucinski, Pawel,Bull, Steven D.
supporting information, p. 513 - 524 (2020/02/13)
A tungsten-based polyoxometalate catalyst employing aqueous H2O2 as a benign oxidant has been used for the solvent free catalytic epoxidation of the trisubstituted alkene bonds of a wide range of biorenewable terpene substrates. This epoxidation protocol has been scaled up to produce limonene oxide, 3-carene oxide and α-pinene oxide on a multigram scale, with the catalyst being recycled three times to produce 3-carene oxide. Epoxidation of the less reactive disubstituted alkene bonds of terpene substrates could be achieved by carrying out catalytic epoxidation reactions at 50 °C. Methods have been developed that enable direct epoxidation of untreated crude sulfate turpentine to afford 3-carene oxide, α-pinene oxide and β-pinene oxide. Treatment of crude epoxide products (no work-up) with a heterogeneous acid catalyst (Amberlyst-15) results in clean epoxide hydrolysis to afford their corresponding terpene-anti-diols in good yields.
Synthetic studies on keramaphidin B: Formation of a macrocyclic ring by intramolecular Diels-Alder reaction
Nakada, Masahisa,Sekine, Daisuke,Shibata, Takahiro,Shimoda, Hiroki
, p. 3 - 11 (2020/01/28)
The possibility of constructing the macrocyclic ring of keramaphidin B via an intramolecular Diels-Alder (IMDA) reaction has been investigated. The IMDA reaction of a substrate possessing dihydropyridone and diene moieties, which were tethered by an alkyl chain including a linear triple bond, was found to proceed in the presence of SnCl4 at 80 °C.
An effective synthesis of acid-sensitive epoxides via oxidation of terpenes and styrenes using hydrogen peroxide under organic solvent-free conditions
Kon, Yoshihiro,Hachiya, Houjin,Ono, Yutaka,Matsumoto, Tomohiro,Sato, Kazuhiko
experimental part, p. 1092 - 1098 (2011/05/14)
An efficient epoxidation process for various terpenes and styrenes using a hydrogen peroxide-tungsten catalytic system with organic solvent-and halide-free conditions was developed. In the presence of the catalytic system, Na 2WO4, PhP(O)(OH)2, and [Me(n-C 8H17)3N]HSO4, and under weak acidic conditions, hydrogen peroxide successfully epoxidized -pinene to -pinene oxide in 95% selectivity at 91% conversion, while the previously published conditions utilizing NH2CH2P(O)(OH)2 as a promoter provided no epoxide. Georg Thieme Verlag Stuttgart.
A strategy for the synthesis of well-defined iron catalysts and application to regioselective diene hydrosilylation
Wu, Jessica Y.,Stanzl, Benjamin N.,Ritter, Tobias
supporting information; experimental part, p. 13214 - 13216 (2010/12/19)
We report the development of a well-defined Fe catalyst and its application to the regio-and stereoselective 1,4-hydrosilylation of 1,3-dienes. To the best of our knowledge, this is the first example of accessing a characterized low-valent Fe catalyst by controlled reductive elimination from a readily accessible Fe precatalyst.
Epoxidation of olefins by β-bromoalkoxydimethylsulfonium ylides
Majetich, George,Shimkus, Joel,Li, Yang
supporting information; experimental part, p. 6830 - 6834 (2011/03/18)
Olefins can be converted to their respective epoxides in a one-pot procedure by dissolving the olefin in anhydrous DMSO, adding NBS to the reaction mixture to generate a β-bromoalkoxydimethylsulfonium ylide, and then adding DBU to the reaction mixture. A large variety of alkenes were successfully epoxi-dized with yields largely dependent on the structure of the alkene. Most importantly, the facial selectivity of this one-pot process is the opposite of that observed when using traditional epoxidizing reagents. Electron-poor alkenes are not epoxidized under these conditions.
An effective catalytic epoxidation of terpenes with hydrogen peroxide under organic solvent-free conditions
Kon, Yoshihiro,Ono, Yutaka,Matsumoto, Tomohiro,Sato, Kazuhiko
scheme or table, p. 1095 - 1098 (2009/09/25)
A catalytic system that operates well for the epoxidation of α-pinene, a very challenging substrate, at near-neutral pH and ambient temperature without organic solvent was developed. With hydrogen peroxide as a terminal oxidant, combination of Na2WO4, PhP(O)(OH) 2, and [Me(n-C8H17)3N]HSO 4 successfully catalyzed the epoxidation of α-pinene to give α-pinene oxide in 95% selectivity at 91% conversion, while the previously published conditions that use NH2CH2P(O)(OH)2 as a promoter provide no epoxide. The method is also well applicable to the epoxidation of the other acidsensitive terpenes. Georg Thieme Verlag Stuttgart.
Zeolite NaY-promoted monocyclization of epoxy polyene terpenes: A unique route for the direct synthesis of incompletely cyclized naturally occurring terpenols
Tsangarakis, Constantinos,Raptis, Christos,Arkoudis, Elias,Stratakis, Manolis
supporting information; experimental part, p. 1587 - 1600 (2009/07/30)
A variety of epoxy polyene terpenes cyclize readily by confinement within zeolite NaY to form primarily products of monocyclization. The monocyclization pathway is highly predominant, irrespectively of the side chain of the epoxy terpene, while the monocyclic products possess regioselectively an exomethylenic double bond. The selective monocyclization in the case of epoxyfarnesyl acetate, epoxyfarnesylacetone or 2,3-epoxysqualene, provides a direct route to the synthesis of a variety of natural products, such as elengasidiol, farnesiferols B-D, achilleol A, camelliol C and to four farnesylacetone-derived metabolites isolated from the brown algae Cystophora monoliformis. The optical rotation of achilleol A derived from the cyclization of (S)-2,3-epoxysqualene matches with that of the natural product, thus the absolute configuration of achilleol A was established as 1S,3R. From the mechanistic point of view, the NaY-promoted cyclization of 9,10-epoxygeranylacetone, selectively deuterium labelled at the C-10 methyl group, is >97% stereoselective with respect to the topicity of the gem-dimethyl group. This result is in agreement with a concerted mechanism. Finally, we have proved through labelling experiments, for the first time, that the biomimetic transformation of epoxy polyene terpenes to 2,3,4-trimethylcyclohexanones upon acid catalysis is a highly stereoselective process. Thus, the less hindered gem-methyl group on the epoxide functionality becomes α- to the carbonyl in the final isomerized product.
