31398-79-5Relevant academic research and scientific papers
An improved method for the protection of carboxylic acids as 1,1-dimethylallyl esters
Sedighi, Minoo,Calimsiz, Selcuk,Lipton, Mark A.
, p. 9517 - 9518 (2006)
(Chemical Equation Presented) 1,1-Dimethylallyl (DMA) esters of various N-protected amino acids have been synthesized using prenyldimethyl-sulfonium tetrafluroborate, a reagent that can be readily made and stored, in conjunction with catalytic CuBr. These reactions were complete within several hours and afforded DMA esters in high yields. As has been previously shown in our group, DMA esters represent a palladium-labile proctecting group for carboxylic acids that resists nucleophilic attack as a tert-butyl ester would.
Gold-catalyzed intramolecular hydroarylation of olefins. Scope evaluation and preliminary mechanistic studies
Jean, Mickael,Van De Weghe, Pierre
supporting information; experimental part, p. 3509 - 3513 (2011/07/09)
We report a gold-catalyzed intramolecular hydroarylation of unactivated olefins using a combination of AuCl3/AgOTf as the catalytic system affording dihydrobenzopyrans, tetralins and tetrahydroquinolines in good yields. For our preliminary mechanistic studies, we have investigated the kinetic isotope effects with deuterated arene compounds and found that this catalytic hydroarylation is consistent with an electrophilic aromatic substitution process.
Irreversible catalytic ester hydrolysis of allyl esters to give acids and aldehydes by homogeneous ruthenium and ruthenium/palladium dual catalyst systems
Nakamura, Asami,Hamasaki, Akiyuki,Goto, Sachihiko,Utsunomiya, Masaru,Tokunaga, Makoto
supporting information; experimental part, p. 973 - 984 (2011/06/19)
An irreversible hydrolysis reaction of allyl esters (1) into carboxylic acids (2) and propanal (3) was achieved with a ruthenium/palladium (Ru/Pd) dual catalyst system. The optimized catalysts consists of a 1:1:1 mixture of (cyclopentadienyl)tris(acetonitrile)ruthenium hexafluorophosphate {[RuCp(MeCN)3] PF6}, bis(acetonitrile)palladium dichloride [PdCl2(MeCN)2] and 1,6-bis(diphenylphosphanyl)hexane (DPPHex). The reaction proceeds via isomerization of allyl esters to 1-propenyl esters and hydrolysis of them to give 2 and 3. The first isomerization step was virtually catalyzed by the Ru components and the second hydrolysis step was mainly catalyzed by the Pd components. The optimized bidentate phosphine (DPPHex) which has long alkylene chain effectively generates two vacant sites on the Ru centers by bridging coordination. When a chelating bidentate phosphine such as DPPE was employed, only one vacant site remained on the Ru center and resulted in a low activity. This chelating Ru complex of DPPE formed even in the presence of 2 equivalents of Ru or additional 1 equivalent of Pd. These differences in coordination behaviour between DPPHex and 1,2- bis(diphenylphosphanyl)ethane (DPPE) cause the differences of the catalytic activity in the first step. The phosphine coordination to Pd center slightly decreases the activity of second hydrolysis step but which was compensated by the increasing of the stability of Pd. On the whole, the optimized Ru/Pd dual catalyst system exhibited good performances on the irreversible hydrolysis of allyl esters.
Iridium-catalyzed hydrocarboxylation of 1,1-dimethylallene: Byproduct-free reverse prenylation of carboxylic acids
In, Su Kim,Krische, Michael J.
, p. 513 - 515 (2008/09/19)
Exposure of carboxylic acids 1a-12a to commercially available 1,1-dimethylallene in the presence of substoichiometric quantities of an iridium catalyst prepared in situ from [Ir(COd)Cl]2 and BIPHEP provides the corresponding 1,1-dimethylallyl (
A convenient, general synthesis of 1,1-dimethylallyl esters as protecting groups for carboxylic acids
Sedighi, Minoo,Lipton, Mark A.
, p. 1473 - 1475 (2007/10/03)
(Chemical Equation Presented) Carboxylic acids were converted in high yield to their 1,1-dimethylallyl (DMA) esters in two steps. Palladium-catalyzed deprotection of DMA esters was shown to be compatible with tert-butyl, benzyl, and Fmoc protecting groups, and Fmoc deprotection could be carried out selectively in the presence of DMA esters. DMA esters were also shown to be resistant to nucleophilic attack, suggesting that they will serve as alternatives to tert-butyl esters when acidic deprotection conditions need to be avoided.
Unsymmetrical Ketone Synthesis via a Three-Component Connection Reaction of Organozincs, Allylating Agents, and Carbon Monoxide
Yasui, Kengo,Fugami, Keigo,Tanaka, Shuji,Tamaru, Yoshinao
, p. 1365 - 1380 (2007/10/02)
A wide variety of organozincs (diethylzinc, alkylzinc halides, and organozincs 2, 5, and 9a-e, functionalized with ester and nitrile groups) undergo a three-component connection reaction with carbon monoxide and allylic benzoates or phosphates 1a-h to furnish unsymmetrical ketones, e.g., 3, 6, and 10, in good yields uder 1 atm of carbon monoxide at ambient temperature by the catalysis of tetrakis(triphenylphosphine)palladium in THF/HMPA.The regio- and stereoselectivities of the present carbonylation show marked contrast to those reported for the palladium-catalyzed carbonylation of usymmetrical allylic substrates.For example, the reaction of crotyl benzoate with octylzinc iodide provides all the possible stereo- and regioisomers, i.e., cis- and trans-2-butenyl and 1-methyl-2-propenyl octyl ketones in comparable amounts.The carbonylative coupling of carvyl phosphates, trans- and cis-1h, and γ-zincio ester 5 is stereospecific and proceeds with inversion of configuration at the allylic stereocenters to furnish cis- and trans-6h, respectively, as single diastereomers.In the absence of HMPA, the reaction feature changes dramatically and lactones 12 and 13 (composed of organozincs, carbon monoxide, and allylating agents in the ratios of 1:1:2 and 2:1:1, respectively) and symmetrical keto diesters 14 (composed of 2 mol of organozincs and 1 mol of carbon monoxide) are formed in varying ratios depending on the reaction conditions.Synthetic scope of the unsymmetrical ketones and mechanistic rationale for these unique and unprecedented reaction behaviors are discussed.
Regiochemistry of alkylation of benzoate and hydrogen dibenzoate anions with 1,1-dimethylallyl and 3,3-dimethylallyl dimethylsulfonium salts. Influence of copper (I)
Gauchet, F.,Julia, M.,Mestdagh, H.,Rolando, C.
, p. 268 - 274 (2007/10/02)
The tertiary allylic sulfonium salt 1,1-dimethylallyl dimethylsulfonium tetrafluoroborate 1 has been synthesized via methylation of (1,1-dimethylallyl) methylsulfide, in order to study its reactivity towards substitution in comparision with the primary isomer.Substitution by a benzoate group is remarkably sensitive to the nature of the nucleophile: whereas the reaction of potassium benzoate with 1 gives a 50:50 mixture of primary and tertiary esters, potassium hydrogen dibenzoate leads exclusively to the tertiary ester.In the presence of copper (I) the tertiary benzoate is the only product obtained with both nucleophiles, as in the case of the corresponding primary sulfonium salt: this result is consistent with the involvement of a ?-allyl copper intermediate common to both isomers.
ALKYLATION DES IONS CARBOXYLATES PAR LES SELS DE SULFONIUM: INFLUENCE DES SELS DE CUIVRE
Badet, B.,Julia, M.,Ramirez-Munoz, M.,Sarrazin, C. A.
, p. 3111 - 3126 (2007/10/02)
Sulfonium salts are extremely powerful alkylating agents, particularly in the two-phase technique both solid-liquid and liquid-liquid.Alkylation of carboxylate salts by sulfonium salts does not show very large dependence on ratio of reactivities of various groups attached to the sulfur and mixtures of esters are often obtained.In the presence of copper(I) salts, there is a strong acceleration of the reaction of allylic sulfonium salts and it becomes very selective in favour of the unsaturated residues.Prenyl sulfonium salts, which react very eficiently through the α-position in the absence of copper salts, give exclusively tertiary esters when a catalytic amount of copper bromide is present.
