7796-72-7Relevant articles and documents
A Synthesis of (±)-Aplydactone
Meier, Robin,Trauner, Dirk
, p. 11251 - 11255 (2016)
Aplydactone is an unusual brominated sesquiterpenoid isolated from the sea hare Aplysia dactylomela. Its highly strained skeleton contains two four- and three six-membered rings and features three adjacent quaternary carbon atoms. Although it is most likely of photochemical origin, attempts to generate it from a chamigrane precursor have failed thus far. In this work, we present a total synthesis of aplydactone that relies on two photochemical key steps that are not biomimetic but highly effective in establishing the two cyclobutane rings. Our synthesis also features an unusual Barbier-type cyclization and culminates in new radical conditions to install the sterically hindered secondary bromide of the natural product.
Intramolecular Hydrogen Atom Transfer Induced 1,2-Migration of Boronate Complexes
Wang, Dinghai,Jana, Kalipada,Studer, Armido
supporting information, p. 5876 - 5879 (2021/08/01)
Radical α-C-H functionalization of alk-5-enyl boronic esters with concomitant functionalization of the alkene moiety is reported. These cascades comprise perfluoroalkyl radical addition to the alkene moiety of a boronate complex, intramolecular hydrogen atom transfer (HAT), single electron oxidation, and 1,2-alkyl/aryl migration. The boronate complexes are readily generated in situ by reaction of the alkenyl boronic esters with alkyl or aryl lithium reagents. Products are formed in a divergent approach by varying carbon radical precursors as well as alkyl/aryl lithium donors, and reactions proceed under mild conditions upon UV irradiation.
Atmospheric Oxygen Mediated Radical Hydrothiolation of Alkenes
McCourt, Ruairí O.,Scanlan, Eoin M.
supporting information, p. 15804 - 15810 (2020/10/26)
A mild, metal-free, atmospheric oxygen-mediated radical hydrothiolation of alkenes (and alkyne) is reported. A variety of sulfur containing motifs including alkanethiols, thiophenols and thioacids undergo an atmospheric oxygen-mediated radical hydrothiolation reaction with a plethora of alkenes in good yield with excellent functional group compatibility, typically with short reaction times to furnish a range of functionalized products. Biomolecules proved tolerant to the conditions and the procedure is robust and easily executable requiring no specialized equipment. Concise mechanistic studies confirm the process proceeds through radical intermediates in a thiol-ene reaction manifold. The methodology offers an efficient “green” approach for thiol-ene mediated “click” ligation and a milder alternative to thermally initiated hydrothiolation processes.
A Sequential Acyl Thiol-Ene and Thiolactonization Approach for the Synthesis of δ-Thiolactones
McCourt, Ruairí O.,Scanlan, Eoin M.
supporting information, p. 3460 - 3464 (2019/05/10)
A novel strategy for the synthesis of δ-thiolactones from inexpensive and readily available ?-unsaturated esters has been developed. This strategy incorporates a radical acyl thiol-ene reaction as the key C-S bond forming step. Cyclization is achieved via a Steglich-type thiolactonization of 5-mercaptopentanoic acids. We report the facile and scalable synthesis of δ-thiolactones in moderate to good yield under mild reaction conditions with tolerance for a range of functional groups.
Pheromone synthesis. Part 264: Synthesis of the core 3-oxabicyclo[3.3.0]octane structures of gomadalactones A, B and C, the components of the contact sex pheromone of the white-spotted longicorn beetle, Anoplophora malasiaca
Mori, Kenji
, p. 3387 - 3398 (2019/05/15)
The core bicyclic cyclopentanelactone structures of gomadalactones A, B and C with α-hydroxyketone system were synthesized from (R)-pulegone, employing deconjugation of an α,β-unsaturated lactone as the key step. Comparison of the CD spectra of the synthetic compounds with those of the natural products confirmed the absolute configuration of the natural pheromone components as proposed in 2007. X-ray crystallographic analysis of the model compound of gomadalactone B core structure was carried out.
Scalable Microwave-Assisted Johnson-Claisen Rearrangement with a Continuous Flow Microwave System
Egami, Hiromichi,Tamaoki, Souma,Abe, Masato,Ohneda, Noriyuki,Yoshimura, Takeo,Okamoto, Tadashi,Odajima, Hiromichi,Mase, Nobuyuki,Takeda, Kazuhiro,Hamashima, Yoshitaka
supporting information, p. 1029 - 1033 (2018/08/03)
We demonstrated the rapid Johnson-Claisen rearrangement of allyl alcohol and triethyl orthoacetate with a continuous flow apparatus combined with a microwave reactor. The reaction could be carried out without solvent, and only a catalytic amount of acetic acid was sufficient to promote the reaction under microwave irradiation conditions. To confirm the optimal reaction conditions found experimentally, we performed Design of Experiments (DoE) by the Nelder-Mead method and a least-squares method regarding the amount of acetic acid and the flow rate. Consequently, the highest yield of the desired γ,δ-unsaturated ester was obtained, and the productivity at the reaction step of the continuous process was 89.5 g/h under the optimal conditions, suggesting that 2.1 kg of the product would be theoretically obtained in 1 day. We also investigated the Johnson-Claisen rearrangement using other allylic alcohols, and the corresponding products were obtained in good to high yields per unit of time.
Rhodium-Catalyzed Cyclization of O,ω-Unsaturated Alkoxyamines: Formation of Oxygen-Containing Heterocycles
Escudero, Julien,Bellosta, Véronique,Cossy, Janine
supporting information, p. 574 - 578 (2018/02/21)
O,ω-Unsaturated N-tosyl alkoxyamines undergo unexpected RhIII-catalyzed intramolecular cyclization by oxyamination to produce oxygen-containing heterocycles. Mechanistic studies show that an aziridine intermediate seems to be responsible for the formation of the heterocycles, possibly via a RhV species.
Enantioselective Synthesis of (+)-Peganumine A
Piemontesi, Cyril,Wang, Qian,Zhu, Jieping
supporting information, p. 11148 - 11151 (2016/10/11)
A gram-scale enantioselective total synthesis of (+)-peganumine A was accomplished in 7 steps from commercially available 6-methoxytryptamine. Key steps included (a) a Liebeskind-Srogl cross-coupling; (b) a one-pot construction of the tetracyclic skeleton from an ω-isocyano-γ-oxo-aldehyde via a sequence of an unprecedented C-C bond forming lactamization and a transannular condensation; (c) a one-pot organocatalytic process merging two achiral building blocks into an octacyclic structure via a sequence of enantioselective Pictet-Spengler reaction followed by a transannular cyclization. This last reaction created two spirocycles and a 2,7-diazabicyclo[2.2.1]heptan-3-one unit with excellent control of both the absolute and relative stereochemistry of the two newly created quaternary stereocenters.
An efficient ring-closing metathesis reaction based approach to 1,2,2-trimethylcyclopentanemethanol. Formal synthesis of (±)-herbertene and (±)-cuparenes
Srikrishna,Satyanarayana
, p. 2465 - 2468 (2007/10/03)
A formal synthesis of the aromatic sesquiterpenes (±)-herbertene and (±)-cuparenes is accomplished via an efficient synthesis of 1,2,2-trimethylcyclopentanemethanol employing a combination of Claisen rearrangement and ring-closing metathesis reactions.
Reaction of orthoesters with alcohols in the presence of acidic catalysts: A study
Sampath Kumar,Joyasawal, Sipak,Reddy,Pawan Chakravarthy,Krishna,Yadav
, p. 1686 - 1692 (2007/10/03)
Allylic and benzylic alcohols are converted into corresponding unsymmetrical ethers when reacted with various orthoesters in the presence of montmorillonite KSF at ambient temperature. A detailed study has been undertaken to examine the mechanism and generality of these reactions with regard to various acidic catalysts, which reveal interesting competitive reactions mainly O-acetylation, together with trace amount of dimerized product. The type of the side product and their relative quantity depends upon the nature of the catalyst employed. Furthermore, the low yields of the Claisen rearrangement product obtained from allylic alcohols under heating is rationalized due to the formation of some of these products.
