4743-73-1Relevant academic research and scientific papers
Novel carbonyl-dependent regioselective allylation via diethylzinc- mediated umpolung of π-allylpalladium
Kimura, Masanari,Ogawa, Yoshimi,Shimizu, Masamichi,Sueishi, Masayuki,Tanaka, Shuji,Tamaru, Yoshinao
, p. 6903 - 6906 (1998)
Palladium-catalyzed allylation of carbonyls (1.1 - 1.5 mmol) with allylic esters 3a-d (1 mmol) in the presence of Pd(PPh3)4 (0.05 mmol) and Et2Zn (2.4 mmol) in THF at room temperature shows marked carbonyl-dependent regioselectivity, providing α-allylation products 5 with benzaldehyde and γ-allylation products 6 with acetone and ethyl acetate.
Diethylzinc-mediated allylation of carbonyl compounds catalyzed by [(NHC)(PR3)PdX2] and [(NHC)Pd(η3-allyl)Cl] complexes
Flahaut, Alexandre,Toutah, Krimo,Mangeney, Pierre,Roland, Sylvain
experimental part, p. 5422 - 5432 (2010/06/15)
[(NHC)(PR3)PdX2] complexes (NHC = N-heterocyclic carbene) are active precatalysts in the palladium-catalyzed allylation of carbonyl compounds with allylic acetates and diethylzinc. A comparative study examining the catalytic activity of a series of six of these complexes was carried out with allyl and cinnamyl acetates. [(IMeSMe)(PPh3)PdI 2] was found to be the most versatile precatalyst (IMesMe = 1-mesityl-3-methylimidazol-2-ylidene) and the scope of the reaction was investigated with this complex. [(IMeSMe)(PPh3)-PdI2] catalyzes the allylation of aromatic (except 4-nitrobenz-aldehyde) and aliphatic aldehydes (including enolizable aldehydes) with cinnamyl acetate to give the corresponding homoallylic alcohols in 57-98 % yields and dlastereoselectivities ranging from 70:30 to 92:8. The allylation of acetone also takes place under the same conditions, leading to the expected adduct in 63 % yield. The reaction with cyclohexenyl acetate proceeds at room temperature to afford the homoallylic alcohols in 40-78% yields with excellent diastereoselec-tivities (>98:2), but is limited to aromatic aldehydes. An experimental study concerning the mechanism, of the transformation was also carried out. We first demonstrated that the phosphane ligand was not essential for the reaction to take place. [(NHC)Pd(allyl)Cl] complexes are active precatalysts and lead to similar yields in the presence or in the absence of PPh3. Transmetalation of [(NHC)Pd(allyl)Cl] complexes with diethyl- or dimethylzinc, which is a determining step for the mechanism, was studied by 1H NMR spectroscopy. The reaction of [(IPr)Pd(allyl)Cl] with dimethylzinc affords rapidly [(IPr)Pd(η3-allyl)(Me)] but no detectable trace of allylzinc species [IPr = 1, 3-bis(2, 6-diisopropylphenyl)imidazol-2-ylidene]. [(IPr)Pd(η3-allyl)(Me)] was found to be a nucleophilic species able to react smoothly at room temperature with an aldehyde in the absence of zinc to form the corresponding homoallylic alcohol.
Arene-catalysed lithiation of phenyl- and 1,1-diphenylcyclopropane: synthetic applications
Gómez, Cecilia,Lillo, Victor J.,Yus, Miguel
, p. 4655 - 4662 (2007/10/03)
The reaction of phenylcyclopropane (1) with an excess of lithium and a catalytic amount of DTBB (2.5% molar) in THF at room temperature, followed by treatment with an electrophile [Me3SiCl, PhMe2SiCl, t-BuCHO, PhCHO, Me2CO
Epoxide formation by ring closure of the cinnamyloxy radical
Amaudrut, Jerome,Wiest, Olaf
, p. 1251 - 1254 (2007/10/03)
(equation presented) Ar = 4-nitrobenzene The cinnamyloxy and oxiranyl benzyl radicals were generated by photolysis of alkyl 4-nitrobenzenesulfenates. The yet unprecedented epoxide ring formation from a primary alkoxy radical was observed. Experimental evidence supports the fact that the mode of ring opening of the oxiranyl carbinyl radical system is thermodynamically driven. B3LYP/6-31G* calculations indicate that the closed form of the radical is ～5 kcal/mol more stable than the open one.
On the Regioselectivity of Coupling of Substituted Allyl Radicals. Steric Versus FMO Control
Pasto, Daniel J.,L'Hermine, Gael
, p. 3259 - 3272 (2007/10/02)
The photo-induced decomposition of substituted-homoallylic 4-nitrobenzenesulfenates produces substituted allyl radicals which undergo dimerization and coupling with the 4-nitrobenzenethiyl radical.The regioselectivity of the dimerization of the allyl redi
