Synthesis of Cyclic and Bicyclic Enaminones from β-Amino Acids

Significance

β-Aminoynones, readily derived from the corresponding amino acids, are converted into 2,3-dihydro-4[1H]-pyridinones under mild conditions in 60-99% yields. The reaction proceeds via Michael addition of chloride and the detectable intermediate (NMR) undergoes methano­lysis and cyclization (proposed intermediate A) to form the final product. The yields and the reaction rates may be improved by using HCl or TMS-I as initial N-Boc deprotection reagents rather than TFA. Aminoynones derived from optically active as well as racemic amino acids were used in these transformations.