22767-77-7Relevant articles and documents
A facile and convenient sequential homobimetallic catalytic approach towards β-methylstyrenes. A one-pot Stille cross-coupling/isomerization strategy
Simonetti, Sebastian O.,Larghi, Enrique L.,Kaufman, Teodoro S.
, p. 3735 - 3743 (2014/06/09)
An efficient one-pot synthetic approach towards β-methylstyrenes is reported. The transformation, based on sequential homobimetallic catalysis, involves a Stille cross-coupling reaction between aryl halides and allyltributylstannane, followed by an in situ palladium-catalyzed conjugative isomerization. The reaction was optimized, and the best results were obtained with 10 mol% Pd(PPh3)2Cl2, 8.0 equiv. LiCl, and 0.5 equiv. PPh3 in diglyme at 130 °C for 12 h. It was demonstrated that the reaction tolerates a wide variety of functional groups. This journal is the Partner Organisations 2014.
One-step method for the synthesis of aryl olefins from aryl aldehydes and aliphatic aldehydes
Borate, Hanumant B.,Gaikwad, Supriya H.,Kudale, Ananada S.,Chavan, Subhash P.,Pharande, Shrikant G.,Wagh, Vitthal D.,Sawant, Vikram S.
supporting information, p. 1528 - 1530 (2013/03/28)
A conceptually new one-step reaction affording unexpected aryl olefinic product from aromatic aldehyde, aliphatic aldehyde and malononitrile in the presence of acetic acid-ammonium acetate under mild reaction conditions without using any metal catalyst is reported. This novel reaction was used to prepare a number of substituted aryl olefins including new molecules.
Wittig reaction: Role of steric effects in explaining the prevalent formation of Z olefin from nonstabilized ylides
Baccolini, Graziano,Delpivo, Camilla,Micheletti, Gabriele
, p. 1291 - 1302 (2012/11/13)
For understanding the mechanism involved in the Wittig reaction, it is important to know the factors which influence the stability of 1,2-oxaphosphetane intermediates with pentacoordinate phosphorus; in these intermediates, the steric factor plays a predominant role. Studying the Wittig reaction between nonstabilized ylides and different aldehydes, we noted that the stereochemical outcome driving toward Z-olefin formation was influenced only by different steric factors. The proposed mechanism differs from those previously reported because it underlines the fundamental role of the two cis/trans oxaphosphetane intermediates with the oxygen atom in equatorial position.
Cross-coupling of aromatic bromides with allylic silanolate salts
Denmark, Scott E.,Werner, Nathan S.
scheme or table, p. 16382 - 16393 (2009/05/08)
The sodium salts of allyldimethylsilanol and 2-butenyldimethylsilanol undergo palladium-catalyzed cross-coupling with a wide variety of aryl bromides to afford allylated and crotylated arenes. The coupling of both silanolates required extensive optimization to deliver the expected products in high yields. The reaction of the allyldimethylsilanolate takes place at 85°C in 1,2-dimethoxyethane with allylpalladium chloride dimer (2.5 mol %) to afford 73-95% yields of the allylation products. Both electron-rich and sterically hindered bromides reacted smoothly, whereas electron-poor bromides cross-coupled in poor yield because of a secondary isomerization to the 1-propenyl isomer (and subsequent polymerization). The 2-butenyldimethylsilanolate (E/Z, 80:20) required additional optimization to maximize the formation of the branched (γ-substitution) product. A remarkable influence of added alkenes (dibenzylideneacetone and norbornadiene) led to good selectivities for electron-rich and electron-poor bromides in 40-83% yields. However, bromides containing coordinating groups (particularly in the ortho position) gave lower, and in one case even reversed, selectivity. Configurationally homogeneous (E)-silanolates gave slightly higher γ-selectivity than the pure (Z)-silanolates. A unified mechanistic picture involving initial γ-transmetalation followed by direct reductive elimination or σ-π isomerization can rationalize all of the observed trends.
Trimethyl phosphite as a trap for alkoxy radicals formed from the ring opening of oxiranylcarbinyl radicals. Conversion to alkenes. Mechanistic applications to the study of C-C versus C-O ring cleavage
Ding, Bangwei,Bentrude, Wesley G.
, p. 3248 - 3259 (2007/10/03)
Trimethyl phosphite, (MeO)3P, is introduced as an efficient and selective trap in oxiranylcarbinyl radical (2) systems, formed from haloepoxides 8-13 under thermal AIBN/n-Bu3SnH conditions at about 80 °C. Initially, the transformations of 8-13, in the absence of phosphite, to allyl alcohol 7 and/or vinyl ether 5 were measured quantitatively (Table 1). Structural variations in the intermediate oxiranylcarbinyl (2), allyloxy (3), and vinyloxycarbinyl (4) radicals involve influences of the thermodynamics and kinetics of the C-O (2 → 3, k1) and C-C (2 → 4, k2) radical scission processes and readily account for the changes in the amounts of product vinyl ether (5) and allyl alcohol (7) formed. Added (MeO)3P is inert to vinyloxycarbinyl radical 4 and selectively and rapidly traps allyloxy radical 3, diverting it to trimethyl phosphate and allyl radical 6. Allyl radicals (6) dimerize or are trapped by n-Bu3SnH to give alkenes, formed from haloepoxides 8, 9, and 13 in 69-95% yields. Intermediate vinyloxycarbinyl radicals (4), in the presence or absence of (MeO)3P, are trapped by n-Bu3SnH to give vinyl ethers (5). The concentrations of (MeO)3P and n-Bu3SnH were varied independently, and the amounts of phosphate, vinyl ether (5), and/or alkene from haloepoxides 10, 11, and 13 were carefully monitored. The results reflect readily understood influences of changes in the structures of radicals 2-4, particularly as they influence the C-O (k1) and C-C (k2) cleavages of intermediate oxiranylcarbinyl radical 2 and their reverse (k-1, k-2). Diversion by (MeO)3P of allyloxy radicals (3) from haloepoxides 11 and 12 fulfills a prior prediction that under conditions closer to kinetic control, products of C-O scission, not just those of C-C scission, may result. Thus, for oxiranylcarbinyl radicals from haloepoxides 11, 12, and 13, C-O scission (k1, 2 → 3) competes readily with C-C cleavage (k2, 2 → 4), even though C-C scission is favored thermodynamically.
New photochemical rearrangements and extrusion reactions of aromatic compounds induced by an intramolecular [2+2] photocycloaddition between a naphthalene and a resorcinol moiety
Hoffmann, Norbert
, p. 7933 - 7941 (2007/10/03)
An intramolecular [2+2] photocycloaddition between a naphthalene and a resorcinyl moiety was followed by an acid catalyzed rearrangement leading to tricyclic tetrahydrofuran derivatives. The reaction was efficient when the irradiation was carried out at 300nm. For the first time, an extrusion of a RCOCH3 (R=H or alkyl) fragment from the tetrahydrofuran ring was observed when the tricyclic tetrahydrofuran derivatives were irradiated at 254nm. Reaction rate and yield depended on the substitution pattern. In particular, significantly different quantum yields were measured in the case of different diastereoisomers.
NiCl2(dppe)-Catalyzed Geminal Dialkylation of Dithioacetals and Trimethylation of Ortho Thioesters
Tzeng, Yih-Ling,Yang, Ping-Fan,Mei, Nai-Wen,Yuan, Tien-Min,Yu, Chun-Chi,Luh, Tien-Yau
, p. 5289 - 5293 (2007/10/02)
NiCl2(dppe)-catalyzed cross-coupling of cinnamaldehyde dithioacetals gave the corresponding geminal dimethylation products in excellent yields.Allylic ortho thioesters afforded regioselectively the corresponding trimethylation products.The reaction may occur via an 18-electron ?-allyl intermediate, which undergoes facile reductive elimination to afford the geminal dimethylation product.Benzylic dithioacetals having an ortho amino group gave 2-isopropylanilines exclusively.The reaction of benzylic dithioacetals with EtMgBr under the same conditions yielded geminal diethylation products.
DIRECT PREPARATION OF SUBSTITUTED OLEFINS FROM EPOXIDES UTILIZING LITHIUM TETRAALKYLCERATE
Ukaji, Yutaka,Fujisawa, Tamotsu
, p. 5165 - 5168 (2007/10/02)
Alkylated olefins were directly synthesized in good yields by the deoxygenation reaction of epoxides with concomitant introduction of the alkyl group using lithium tetraalkylcerate.Styreneoxide and (1-naphtyl)ethyleneoxide gave terminal olefins, while ethyleneoxide replaced by alphatic substituent, 1,2-epoxy-4-phenylbutane, afforded internal olefin.The utility of the present method was demonstrated in the one-step synthesis of a sesquiterpene, dehydro-α-curcumene.
