54795-99-2Relevant academic research and scientific papers
Palladium-catalyzed cross-coupling of aryl and alkenyl boronic acids with alkenes via oxidative addition of a carbon-boron bond to palladium(0)
Cho, Chan Sik,Uemura, Sakae
, p. 85 - 92 (1994)
Arylboronic acids react with alkenes in acetic acid at 25 deg C in the presence of a catalytic amount of palladium(II) acetate together with sodium acetate to give the corresponding aryl-substituted alkenes in high yields.Alkenylboronic acids react with alkenes under similar conditions to give the corresponding conjugated dienes stereospecifically, but the product yields are lower, compared with those from arylboronic acids.Similar treatment of sodium tetraphenylborate (NaBPh4) with alkenes also affords the corresponding phenylated alkenes in high yields together with biphenyl and benzene as side products.Oxidative addition of a carbon-boron bond to palladium(0), formed in situ, to give an organopalladium(II) species is assumed to be the key step of these cross-coupling reactions. Key words: Boronic acid; Aryl; Alkenyl; Alkene; Palladium; Oxidative addition
Conformations and Rotational Barriers of 1,3-Diphenylallyllithium Compounds
Boche, Gernot,Buckl, Klaus,Martens, Diether,Schneider, Dieter R.
, p. 1135 - 1171 (2007/10/02)
The phenyl substituents of the 1,3-diphenylallyl anions 10 (gegenion lithium, solvent tetrahydrofuran) can exist in the exo,exo-, endo,exo- and/or endo,endo-conformations.We have investigated the influence of substituents R at C2 on the equilibria of these solvent separated ion pairs.While 10a (R = H) is the only one to exist predominantly in the exo,exo-conformation, and in 10b and c (R = CH3 and CN, respectively) the endo,exo-conformers predominate, in 10d, e and f (R = C2H5, C6H5 and iPr, respectively) there is increasing preference for the endo,endo-conformation, which in 10g (R = tBu) is the dominant (>/= 95percent) conformation.A vast congestion in the endo,endo-conformation is avoided by a rotation of the phenyl rings out of the plane of the allyl carbon atoms, and an expansion of the sp2 angles in the allyl moiety.The rotational barriers around the allyl anion bonds decrease from 19.1 kcal*mol-1 (10a) to 12.5 kcal*mol-1 (10f).Since this trend parallels to the above mentioned shift of the equilibria, it is due to ground state effects.The rotational barriers are only slightly (10a,b) if at all influenced by gegenion effects, which is in sharp contrast to the parent allyl "anion".Therefore, the rotational barriers of the allyl anions 10 are qualified for a comparison with the corresponding radicals and cations.Furthermore, with ΔG(excit)273 deg C = 19.1 kcal*mol-1 as a lower limit value for the rotational barrier of the parent allyl anion, one can estimate that the true value of this species must be close to barriers calculated with STO-3G and 4-3l-G programs (ca. 26 kcal*mol-1).
