121642-38-4Relevant articles and documents
Unsaturated Carboxylic Acid Dienolates. Reaction with Substituted Cyclohexanones and Unsubstituted Cycloalkanones. Regio- and Stereoselectivity
Ballester, Pablo,Costa, Antonio,Garcia-Raso, Angel,Mestres, Ramon
, p. 21 - 32 (2007/10/02)
Regio- and stereo-selectivities for the reaction of lithium dienolates derived from crotonic and dimethylacrylic acids with substituted cyclohexanones (4)-(6) are found to depend on reaction time and temperature. α-Adducts resulting from equatorial attack predominate after a short time at -70 deg C, but axial approach and γ-addition are favoured by longer reaction time and higher temperature.Inversion of axial/equatorial stereoselectivity is observed for some cyclohexanones.For unsubstituted cycloalkanones, regioselectivity is dependent on ring size.This effect can be explained on the basis of Brown's "I-strain" rationalization.For C5-C12 ketones, γ-adducts are found when reactions are carried out above room temperature, but at 0 deg C, C5, C6, and C12 cycloalkanones yield α-isomers whereas mesocyclic ketones afford γ-isomers.