79605-63-3Relevant articles and documents
Interactions of cationic palladium(II)- and platinum(II)-η3- allyl complexes with fluoride: Is asymmetric allylic fluorination a viable reaction?
Hintermann, Lukas,Laeng, Florian,Maire, Pascal,Togni, Antonio
, p. 1397 - 1412 (2007/10/03)
The complex cations [M(η3-R2All)(PPFPz{3-tBu})] + (M = PdII, R2All = 1,3-diphenylallyl, 1,3-dicyclohexylallyl, indenyl; M = PtII, R2All = 1,3-diphenylallyl; PPFPz-{3-tBu} = 3-tert-butyl-1-{1-[2-diphenylphosphanyl- ferrocenyl]ethyl}-1H-pyrazole) have been prepared as salts with PF 6- or SbF6-. They have been characterized by NMR spectroscopy in solution and by X-ray crystallography in the solid state. Their reactions with sources of nucleophilic and "naked" fluoride have been investigated by multinuclear NMR spectroscopy. The PdII complexes did not undergo any nucleophilic substitution with concomitant release of allyl fluorides. The dicyclohexylallyl fragment was released as a 1,3-diene by elimination, but with other allyl complexes nonspecific decomposition reactions predominated. The complex [Pt(η3-1,3-Ph2C3H3)-(PPFPz{3- tBu})]PF6 underwent an anion exchange with Me4NF to give [Pt(1,3-Ph2C3H3)(PPFPz{3-tBu})]F which existed as a mixture of interconverting allyl isomers in solution at ambient temperature. For the bromide salt, [Pt(η3-1,3-Ph 2C3H3)(PPFPz{3-tBu})]Br, allyl isomerization was slow at ambient temperature. Precursors of Pt0 reacted with bromo-1,3-diphenylprop-2-ene to give [Pt2(μ-Br) 2(η3-1,3-Ph2All)2] and precursors of Pd0 underwent oxidative additions with bromo- and fluoro-1,3-diphenyl-2-propene to give 1,3-diphenylallyl complexes of Pd II. Therefore, the nucleophilic attack of fluoride on the allyl fragment of PdII complexes is endergonic, and the high energy barrier of this step is difficult to overcome in a catalytic allylic fluorination reaction. Wiley-VCH Verlag GmbH & Co. KGaA, 2006.
A Tellurium Transposition Route to Allylic Alcohols: Overcoming Some Limitations of the Sharpless-Katsuki Asymmetric Epoxidation
Dittmer, Donald C.,Discordia, Robert P.,Zhang, Yanzhi,Murphy, Christopher K.,Kumar, Archana,et al.
, p. 718 - 731 (2007/10/02)
Good yields of enantiomeric allylic alcohols can be obtained in high enantiomeric excess (ee) by combining Sharpless-Katsuki asymmetric epoxidation process (SAE) with tellurium chemistry.The advantages of the tellurium process are as follows: (1) the 50percent yield limitation on the allylic alcohol in the Sharpless kinetic resolution (SKR) can be overcome; (2) allylic tertiary alcohols which are unsatisfactory substrates in the SKR can be obtained in high optical purity; (3) optically active secondary allylic alcohols with tertiary alkyl substituents (e.g. tert-butyl) at C-1 can be obtained in high ee; (4) optically active sterically congested cis secondary alcohols can be obtained in high ee; and (5) the nuisance of the slow SAE of some vinyl carbinols can be avoided.The key step in the reaction sequence is either a stereospecific 1,3-transposition of double bond and alcohol functionalities or an inversion of the alcohol configuration with concomitant deoxygenation of the epoxide function in epoxy alcohols.Trans secondary allylic alcohols can be converted to cis secondary allylic alcohols by way of erythro epoxy alcohols (glycidols); threo glycidyl derivatives are converted to trans secondary allylic alcohols.These transformations are accomplished by the action of telluride ion, generated in situ from the element, on a glycidyl sulfonate ester.Reduction of elemental Te is conveniently done with rongalite (HOCH2SO2Na) in an aqueous medium.This method is satisfactory when Te2- is required to attack at primary carbon site of a glycidyl sulfonate.In cases where Te2- is required to attack a secondary carbon site, reduction of the tellurium must be done with NaBH4 or LiEt3BH.Elemental tellurium is precipitated during the course of the reactions and can be recovered and reused.
Telluride-mediated stereospecific conversion of racemic E-allylic alcohols to homochiral Z-allylic alcohols; transposition of primary and secondary allylic alcohols via glycidol derivatives
Discordia, Robert P.,Murphy, Christopher K.,Dittmer, Donald C.
, p. 5603 - 5606 (2007/10/02)
Racemic trans-secondary allylic alcohols can be converted to homochiral cis-secondary allylic alcohols by means of a telluride-mediated transposition reaction applied to the homochiral glycidol obtained from a Sharpless kinetic resolution. (+)-Linalool is obtained in>95% enantiomeric excess from geraniol, an example of a transposition of a primary allylic alcohol to a homochiral tertiary alcohol.
