66434-99-9Relevant academic research and scientific papers
C-H Alkenylation of Heteroarenes: Mechanism, Rate, and Selectivity Changes Enabled by Thioether Ligands
Gorsline, Bradley J.,Wang, Long,Ren, Peng,Carrow, Brad P.
supporting information, p. 9605 - 9614 (2017/07/24)
Thioether ancillary ligands have been identified that can greatly accelerate the C-H alkenylation of O-, S-, and N-heteroarenes. Kinetic data suggest thioether-Pd-catalyzed reactions can be as much as 800× faster than classic ligandless systems. Furthermore, mechanistic studies revealed C-H bond cleavage as the turnover-limiting step, and that rate acceleration upon thioether coordination is correlated to a change from a neutral to a cationic pathway for this key step. The formation of a cationic, low-coordinate catalytic intermediate in these reactions may also account for unusual catalyst-controlled site selectivity wherein C-H alkenylation of five-atom heteroarenes can occur under electronic control with thioether ligands even when this necessarily involves reaction at a more hindered C-H bond. The thioether effect also enables short reaction times under mild conditions for many O-, S-, and N-heteroarenes (55 examples), including examples of late-stage drug derivatization.
Highly Efficient Pd-Catalyzed Coupling of Arenes with Olefins in the Presence of tert-Butyl Hydroperoxide as Oxidant
Jia, Chengguo,Lu, Wenjun,Kitamura, Tsugio,Fujiwara, Yuzo
, p. 2097 - 2100 (2008/02/10)
(matrix presented) ArH : benznoid and non-benzenoid. R = H, CH3, Ph. R1 = Ph, CO2Et, COMe, CHO, CO2H, CN. The oxidative coupling of arenes with olefins has been performed efficiently in the presence of catalytic amounts of palladium acetate and benzoquinone (BQ) with tert-butyl hydroperoxide as the oxidant in up to 280 turnover numbers (TON). The catalytic system is especially active for the coupling of heterocycles such as furans and indole with activated olefins. The reaction is highly regio-and stereoselective, giving trans-olefins predominantly.
Michael addition of aromatic heterocyclic compounds to α,β-unsaturated ketones. 3-Oxoalkylation of furans, indoles and thiophenes.
Dujardin, Gilles,Poirier, Jean-Marie
, p. 900 - 909 (2007/10/02)
The Lewis-acid catalyzed Michael-type addition of aromatic heterocyclic compounds, such as furans, indoles and thiophenes, to α,β-unsaturated ketones (including methyl vinyl ketone) was performed in mild conditions in the presence of boron trifluoride etherate and an alcohol.Rosethiophene was prepared in a synthesis involving a few steps. - Keywords: Michael addition / boron trifluoride etherate / but-3-ene-2-one / 3-oxoalkylation / rosethiophene
Thermal Reactions of Epoxyenones and Epoxydienes in the Ionone Series
O'Sullivan, Anthony,Bischofberger, Norbert,Frei, Bruno,Jeger, Oskar
, p. 1089 - 1106 (2007/10/02)
On flash vacuum thermolysis at temperatures between 390 and 585 deg C, the epoxyenones 1-9 and the epoxydienes 10-12 undergo various types of reactions involving C-C and/or C-O bond cleavage in the oxirane ring.Thus, the compounds 1, 4-9, 11, and 12 were transformed to the divinyl ethers 13, 20, 21, 24, 25, 29, and 38 by a reversible homosigmatropic H-shift.On thermolysis of the epoxides 1-12, several products formed via carbonyl-ylide intermediates were also isolated.The extent of the formation of ylide products is clearly related to the conjugating ability of the functional groups neighboring the oxirane.Thus, the epoxides 3, 5, and 7-10 bearing a C(3)=C(4) bond, a 5-oxo function, a 3,4-epoxy or a 3,4-methano group, preferentially underwent reactions via a carbonyl-ylide intermediate.As a further reaction pathway, the epoxides 1-12 undergo cleavage of the C-O bonds of the oxirane, which, however, is presumably an acid-catalyzed rather than a thermal reacion.
Novel Bicycloannulation via Tandem Vinylation and Intramolecular Diels-Alder Reaction of Five-Membered Heterocycles: A New Approach to Construction of Psoralen and Azapsoralen
Hayakawa, Kenji,Yodo, Mitsuaki,Ohsuki, Satoru,Kanematsu, Ken
, p. 6735 - 6740 (2007/10/02)
trans-4-(Phenylsulfinyl)-3-buten-2-one (1) was found to undergo a new versatile addition-elimination reaction with five-membered compounds such as furans, pyrroles, imidazole, pyrazole, and 6-(dimethylamino)fulvene to give an excellent yield of the corresponding trans-4-aryl-3-buten-2-ones (3).The thermal reaction of the propargyl ethers 7a,b prepared from 3a,b gave a single intramolecular Diels-Alder adduct, 8a,b, in 59percent and 38percent yields, respectively.Treatment of 7a,b with t-BuOK in refluxing tert-butyl alcohol afforded another type of Diels-Alder adduct, 10a,b, in almost quantitative yields.This bicycloannulation strategy was applied to a new synthesis of psoralen which is of current interest due to its unique photoreactivity with DNA.The acid-catalyzed reaction of sulfoxide 12, prepared from ethyl acatoacetate in high yield, with furan gave 13 in 78percent yield.The intramolecular Diels-Alder reaction of the neopentyl acetal of 13 in the presence of Pd/C followed by acid hydrolysis afforded the tricyclic ketone 18 in 38percent yield.Baeyer-Villiger oxidation and dehydrogenation of 18 completed the synthesis of psoralen (11).Furthermore, hitherto unknown azapsoralen 20 was also synthesized by this method.
Zur vinylogen β-Spaltung von Enonen. UV.-Bestrahlung von 4-(3',7',7'-Trimethyl-2'-oxabicyclohept-3'-en-1'-yl)but-3-en-2-on
Murato, Kazuo,Wolf, Hans Richard,Jeger, Oskar
, p. 215 - 223 (2007/10/02)
On 1?,?*-excitation (λ=254 nm) in acetonitrile (E/Z)-2 is converted into the isomers 4-9 and undergoes fragmentation yielding 10; in methanol (E/Z)-2 gives 7-10 and is transformed into 11 by incorporation of the solvent. On 1?,?*-excitation (λ>347 nm; benzene-d6) (E)-2 is isomerized into (Z)-2, which is converted into the isomers 3 and further 4 by further irradiation. 1?,?*-Excitation (λ=254 nm; acetonitrile) of 4 gives 6 and (E)-9, whereas UV.-irradiation (λ=254 nm; acetonitrile-d3) of 5 yields (E)-7 and 8. On 1?,?*-excitation (λ=254 nm; acetonitrile) of (E/Z)-12 the compounds (E)-14 and (E)-15 are obtained.
