84473-25-6Relevant articles and documents
Conjugative interaction in styrenes
Von Doering,Benkhoff, Johannes,Carleton, Peter Smart,Pagnotta, Marco
, p. 10947 - 10955 (2007/10/03)
Conjugative interactions of the carbon-carbon double bond are fundamental in organic chemistry. In this work, equilibria are established among conjugated and unconjugated isomers of two β-substituted styrenes, 1-phenylbut-1-ene and 1-phenyl-3-methylbut-1-ene, and one α,β-disubstituted styrene, 2-phenyl-5-methylhex-2-ene, over a range of temperatures (the van't Hoff method) in hexamethylphosphoric triamide and potassium tert-butoxide. From the trans styrenes of the first two sets, an enthalpy of conjugative interaction of phenyl vis-a-vis alkyl (ΔΔH(ConjInter/Alk)) = -2.5 ± 0.2 kcal/mol [-5.1 kcal/mol defined as phenyl vis-a-vis hydrogen (ΔΔH(ConjInter/H))] is observed, while the cis styrenes reveal an attenuated ΔΔH(ConjInter/Alk) of -1.1 kcal/mol (ΔΔH(ConjInter/H)) = -2.7 kcal/ mol). The α-methyl group in the third set also leads to a reduced conjugative interaction. Entropy plays an important role in determining positions of equilibrium. Free energies of conjugation are reported for several sterically hindered o-methyl-substituted styrenes.
Alkylation of Allylic Derivates. 4. On the Mechanism of Alkylation of Allylic N-Phenylcarbamates with Lithium Dialkylcuprates
Goering, Harlan L.,Kantner, Steven S.,Tseng, Chung Chyi
, p. 715 - 721 (2007/10/02)
Alkylation of allylic N-phenylcarbamates by deprotonation, complexation with CuI in THF, and addition of 1 equiv of RLi results in syn γ-alkylation in both cyclic and acyclic systems.This procedure gives higher stereo- and regiospecificity than when allylic N-phenylcarbamates are reacted with 3 equiv of etheral LiCuR2.A mechanism is presented which incorporates an intramolecular oxidative addition leading to a ?-allyl complex (3) which undergoes reductive elimination to give the syn γ-alkylation product.
