Condensation of Crotonic and Tiglic Acid Dianions with Aldehydes and Ketones

Article abstract of DOI:10.1021/jo00197a019

The lithium dianions of crotonic and tiglic acids reacted with n-heptanal, benzaldehyde, isobutyraldehyde, 2,2-dimethyl-3,3-dimethoxypropionaldehyde, acetone, and cyclopentanone at -78 deg C, room temperature, and 65 deg C to give α- and γ-condensation products.The kinetically controlled pathway gives largely or entirely the β-hydroxy acid from condensation at the α-carbon, but at higher temperature the reaction is reversible leading to the more stable δ-hydroxy α,β-unsaturated acid.In addition to the reaction temperature, steric effects associated with both the carbonyl electrophile and the acid dianion were found to influence the α:γ ratio of condensation products.