28525-63-5Relevant academic research and scientific papers
Enantioselective Bromolactonization of Trisubstituted Olefinic Acids Catalyzed by Chiral Pyridyl Phosphoramides
Nishikawa, Yasuhiro,Hamamoto, Yuhta,Satoh, Rika,Akada, Naho,Kajita, Shuhei,Nomoto, Marina,Miyata, Megumi,Nakamura, Madoka,Matsubara, Chinatsu,Hara, Osamu
supporting information, p. 18880 - 18885 (2018/12/04)
Enantioselective bromolactonization of trisubstituted olefinic acids producing synthetically useful chiral lactones with two contiguous asymmetric centers has remained mainly unexplored except for the 6-exo cyclization mode. In this work, the 5-exo- and 6
Controlling 6-endo-selectivity in oxidation/bromocyclization cascades for synthesis of aplysiapyranoids and other 2,2,6,6-substituted tetrahydropyrans
Brücher, Oliver,Bergstr??er, Uwe,Kelm, Harald,Hartung, Jens,Greb, Marco,Svoboda, Ingrid,Fuess, Hartmut
supporting information; experimental part, p. 6968 - 6980 (2012/09/07)
A cascade, composed of (i) oxovanadium(V)-catalyzed oxidation of bromide by tert-butyl hydroperoxide and (ii) stereoselective 6-endo-bromocyclization, affords 3-bromo-2-aryl-2,6,6-trimethyltetrahydropyrans from styrene-type tertiary alkenols in synthetically useful yields. (E)-Alkenols add the bromo- and the alkoxy substituent anti-selectively across the double bond, indicating a bromonium ion-mechanism for the ring closure. 6-endo-control of the alkenol cyclization thereby arises from the polar effect of the aryl substituent. Two methyl substituents bound to the alkene terminus are not similarly able to favor 6-endo-cyclization, because strain arising from methyl group repulsion, as the bromonium-activated π-bond and the hydroxyl oxygen approach, directs bromocyclization of tertiary prenyl-type substrates toward tetrahydrofuran formation. A hexasubstituted bromotetrahydropyran prepared from the oxidation/bromocyclization cascade served as starting material for synthesis of racemic aplysiapyranoid A, in a sequence of free radical and polar functional group interconversion.
Selenium-catalyzed regioselective cyclization of unsaturated carboxylic acids using hypervalent iodine oxidants
Singh, Fateh V.,Wirth, Thomas
supporting information; experimental part, p. 6504 - 6507 (2012/02/02)
A new and convenient selenium-catalyzed regioselective cyclization of γ, δ-unsaturated carboxylic acids to the corresponding 3, 6-dihydro-2Hpyran- 2-ones is described. The cyclization products have been obtained in good to excellent yields using diphenyl diselenide as a catalyst and [bis(trifluoroacetoxy)iodo]benzene as a stoichiometric oxidant 2011 American Chemical Society.
Preparation and reactions of Mn2(CO)9(η1-aldehyde) complexes
Bullock, R. Morris,Rappoli, Brian J.
, p. 1659 - 1669 (2007/10/02)
The reaction of HMn(CO)5 with RMn(CO)5 (R = CH3,p-CH3C6H4, or CH2CH2CH=C(Ph)CH3) gives Mn2-(CO)9(η1-RCHO) complexes. It is suggested that these Mn2(CO)9(η1-aldehyde) complexes may provide a model for a previously unobserved intermediate in the formation of aldehydes from the hydroformylation of olefins. The η1-aldehyde ligand is weakly bound to the manganese, as evidenced by its facile displacement by ligands such as CO, PPh3, and CH3CN. The kinetics of the reaction of HMn(CO)5 with (CO)5Mn(CH2CH2CH=C(Ph)CH3) were studied by 1H NMR at 25 °C in C6D6. The reaction is first-order in the manganese alkyl complex, and the rate of the reaction decreases slightly with increasing concentration of HMn(CO)5. A negligible isotope effect (kH/kD = 1.04 ± 0.09) was found for the reaction of (CO)5Mn(CH2CH2CH= C(Ph)CH3) with DMn(CO)5. The reaction of Mn2(CO)9(η1-CH3CHO) with excess HMn(CO)5 takes several days at room temperature and produces ethanol and the manganese cluster complex Mn3(CO)9(μ3-OEt)2(μ 2-OEt).
A New Approach to Aromatic Substitution - para-Specific Alkylation of Acetophenone by Alkyl Radicals in Strongly Acidic Media
Din, Laily Bin,Meth-Cohn, Otto,Walshe, Nigel D. A.
, p. 781 - 786 (2007/10/02)
Acetophenone in 25percent oleum is substituted by various alkyl radicals specifically in the para-position.The radicals used include cyclohexyl, 3-chloro-1-methylpropyl, 3-bromo-1-methylpropyl, 4-chloro-1-methylbutyl, 4-bromo-1-methylbutyl, 5-bromo-1-methylpentyl, 5-acetoxy-1-methylpentyl, 3-carboxy-1-methylpropyl, 4-carboxy-1-methylbutyl and 5-carboxy-1-methylpentyl.They were all generated by hydrogen atom abstraction at the radical position by dimethylaminium radicals, generated in turn from protonated dimethylchloramine and ferrous sulphate.Yields were generally poor to moderate but utilised simple conditions and cheap reagents.
