63064-14-2Relevant academic research and scientific papers
1,2- Vs 1,4-Regioselectivity of Lithiated Phenylacetonitrile toward α,βUnsaturated Carbonyl Compounds. 2. Relation between the Regioselectivity and the Structure of the Species in Solution
Strzalko, Tekla,Seyden-Penne, Jacqueline,Wartski, Lya,Corset, Jacques,Castella-Ventura, Martine,Froment, Francoise
, p. 3295 - 3301 (2007/10/03)
In THF and THF-toluene media, the reaction of lithiated phenylacetonitrile (1) with benzylide-neacetone (5), at low temperature, led to the same ratio of 1,2- and 1,4-adducts after 5 or 30 min of reaction time. The concentrations of the monomeric bridged ion pair 2 preferentially formed in THF and of the dimer of ion pairs 4 predominating in media that favor association such as THF-toluene solvent mixtures were measured from the IR-integrated intensities of the v (C≡N) bands. These concentrations were quantitatively related to the concentrations of the 1,2- and 1,4-adducts, respectively. All these results evidence the kinetic control of this reaction. Intermediate complexes that take into account the peculiar geometries of the monomer 2 and the dimer 4 are proposed to interpret the different regioselectivities observed with 5. This study is extended to cyclic α-enones and cinnamaldehyde. Similar trends hold for the former, while cinnamaldehyde always leads to 1,2-addition. The formation of intermediate complexes allows us to rationalize the cinnamaldehyde behavior but is insufficient to explain the 1,4-addition with cyclic α-enones lying in an s-trans conformation.
