34737-39-8Relevant academic research and scientific papers
A short access to (+)-ptilocaulin
Cossy, Janine,BouzBouz, Samir
, p. 5091 - 5094 (1996)
A short access to (+)-ptilocaulin involving a photoreductive cyclopropane ring opening of an optically active bicyclo(4.1.0)heptanone derivative is described.
Formation of contiguous quaternary and tertiary stereocenters by sequential asymmetric conjugate addition of grignard reagents to 2-substituted enones and mg-enolate trapping
Germain, Nicolas,Alexakis, Alexandre
, p. 8597 - 8606 (2015/06/02)
Herein a comprehensive study is provided on the asymmetric conjugate addition (ACA) of Grignard reagents to α-substituted cyclic enones. After the elucidation of the optimal experimental conditions, the scope of Grignard reagents and Michael acceptors was examined. Whereas secondary Grignards gave better enantioselectivities with 2-cyclopentenones, both linear and branched Grignard reagents were tolerated for the ACA to 2-methylcyclohexenone. The sequential ACA-enolate trapping, which leads to quaternary stereocenters, was then studied. Thus, many electrophiles have been tested, thereby giving rise to highly functionalized cyclic ketones with contiguous α-quaternary and β-tertiary centers. The present technique is believed to bring a new approach to versatile terpenoid-like skeletons of bioactive natural products. Straightforward derivatizations of enantioenriched saturated cyclic ketones further support the potential of the present methodology in synthesis.
Preparation of o-Fluorophenols from Nonaromatic Precursors: Mechanistic Considerations for Adaptation to Fluorine-18 Radiolabeling
Yasui, Norio,Mayne, Christopher G.,Katzenellenbogen, John A.
supporting information, p. 5540 - 5543 (2015/12/01)
The preparation of fluorine-18 labeled o-fluorophenols at high specific activity is challenging and requires use of [18F]fluoride ion as the radioisotope source. As a novel, alternative approach, we found that treatment of α-diazocyclohexenones with Selectfluor and Et3N·3HF followed by HF elimination and tautomerization afforded o-fluorophenols regioselectively and rapidly. To adapt this chemistry to 18F radiolabeling, using bromine electrophiles in place of Selectfluor gave the o-fluorophenol via an α-bromo-α-fluoroketone intermediate in lower but still reasonable yields.
Versatile CuI/Pd0 dual catalysis for the synthesis of quaternary α-allylated carbonyl compounds: Development, mechanistic investigations and scope
Nahra, Fady,Mace, Yohan,Boreux, Arnaud,Billard, Francois,Riant, Olivier
, p. 10970 - 10981 (2014/09/17)
We report herein a versatile cooperative dual catalysis reaction based on a CuI/Pd0 system. Mechanistic investigation shows that every component plays a crucial role in determining the reaction outcome. The reaction is successfully extended to various substrates; such as α,β-unsaturated ketones, malonates and coumarins. The strategy tolerates different substitution patterns and affords good yields for each family of substrates.
Copper/palladium-catalyzed 1,4 reduction and asymmetric allylic alkylation of α,β-unsaturated ketones: Enantioselective dual catalysis
Nahra, Fady,Mace, Yohan,Lambin, Dominique,Riant, Olivier
, p. 3208 - 3212 (2013/04/23)
Cooperative efforts: The catalytic coupling of the two organometallic intermediates is possible through a Cu/Pd-based dual catalysis (see scheme; LG=leaving group), in which the CuI catalytic cycle generates catalytically the starting material
Strictly regiocontrolled α-monosubstitution of cyclic carbonyl compounds with alkynyl and alkyl groups via Pd-catalyzed coupling of cyclic α-iodoenones with organozincs
Negishi, Ei-Ichi,Tan, Ze,Liou, Show-Yee,Liao, Baiqiao
, p. 10197 - 10207 (2007/10/03)
The conditions for the Pd-catalyzed cross coupling of cyclic α-iodoenones, such as 2-iodo-2-cyclohexenone, with alkynylzincs have been optimized. The use of tris(o-furyl)phosphine (TFP) as a ligand and DMF as a solvent has led to the formation of α-alkynylenones in excellent yields. This optimized procedure has been applied to the synthesis of (±)-harveynone and (±)-tricholomenyn A in high yields. Investigation of related α-alkylation reactions using alkylzincs has revealed the following. Methylzinc and primary alkylzinc derivatives readily undergo Pd-catalyzed cross coupling with α-iodoenones. Although (s-Bu)2Zn also undergoes Pd-catalyzed cross coupling, only the n-Bu-substituted products were obtained, α-Benzylation and α-homobenzylation can proceed satisfactorily, whereas allylzinc and propargylzinc derivatives undergo only addition to the carbonyl group. Although some promising results have been obtained in α-homoallylation and α-homopropargylation, these reactions need to be further improved. (C) 2000 Elsevier Science Ltd.
Carbon-carbon bond formation by electrochemical catalysis in conductive microemulsions
Gao, Jianxin,Rusling, James F.,Zhou, De-Ling
, p. 5972 - 5977 (2007/10/03)
Bicontinuous microemulsions made from oil, water, and surfactants were examined as substitutes for organic solvents in carbon-carbon bond-forming reactions. Conjugated additions of primary alkyl iodides 3a-c to 2-cyclohexen-1-one (4) to give 3-alkyl cyclohexanones 5a-c and cyclization of 2-(4-bromobutyl)-2-cyclohexen-1-one (9) to 1-decalone (10) were mediated by the Co(I)L complex vitamin B12s generated at carbon cloth electrodes under mild conditions. Reaction of the Co(I)L nucleophile with the alkyl halides gives a Co-alkyl complex. Cleavage of the Co-alkyl complexes by using an electrode potential of -0.85 V (all vs SCE) and irradiation with visible light, or a potential of -1.45 V in the dark, were compared. Addition of the resulting alkyl radicals to the activated double bonds gave comparable yields of 3-alkylcyclohexanone 5a-c (70-80% using -0.85 V + light) and 1-decalone (90%, both cleavage modes) 10 in microemulsions and in DMF. Microemulsions containing hexadecyltrimethylammonium bromide (CTAB) gave remarkable stereoselectivity for the trans isomer of 10, while homogeneous DMF and a sodium dodecylsulfate (SDS) microemulsion gave little stereoselectivity.
SYNTHESES DE CYCLOHEXENONES α-SUBSTITUEES VIA LA THERMOLYSE DE CETOSULFOXYDES TERTIAIRES
Barillier, Daniel,Benhida, Rachid,Vazeux, Michel
, p. 83 - 96 (2007/10/02)
The sulfenylation-dehydrosulfenylation method, combined with carbon-carbon bond forming reactions, has been applied to the synthesis of some α-functionalized cyclohexenones 3.Hence, the sodium anion of the 2-methylthiocyclohexanone in THF reacts with primary, allyl and benzyl halides as well as with Michael acceptors to lead to the tertiary ketosulfides 1a-j.Further oxidation by NaIO4 and thermolysis in boiling toluene of the resulting sulfoxides 2 have been performed.The scope and limitations of this strategy are also discussed. Key Words: α-functionalized cyclohexenones; tertiary ketosulfides and ketosulfoxides; sulfenylation and deshydrosulfenylation; thermolysis.
A Stereoselective Organopalladium Route toward Perhydrohistrionicotoxin
Tanner, David,Sellen, Mikael,Baeckvall, Jan-E.
, p. 3374 - 3378 (2007/10/02)
An efficient stereocontrolled route to the spirocyclic alkaloid perhydrohistrionicotoxin (2) is described.The readily available 2-substituted 1,3-cyclohexadiene 4 was converted regio- and stereoselectively to the chloro acetate 5 by using organopalladium methodology.Chemoselective SN2' displacement of the chloride via a copper-catalyzed Grignard reaction furnished 6, thus establishing the correct relative configuration at two adjacent centers.Further elaboration to the δ-amino alkene 10 was followed by a completely stereoselective iodocyclization reaction which yielded azaspirocycle 11.This compound was transformed to depentylperhydrohistrionicotoxin (3) in essentially one operation, thus completing a formal total synthesis of the title alkaloid.The overall yield of 3 from 4 was 23percent for nine operations.An alternative route to advanced intermediate 8 was also developed, the key step being the coupling of enol triflate 15 with the appropriate lithium organocuprate reagent.
