Reaction of the conjugate base of propenylpyrrolidonocarbene chromium pentacarbonyl complex with electrophiles

The conjugate base of pentacarbonyl(propenylpyrrolidinocarbene)chromium(0) I and II (e.g., R = H, D, Me, Et) is easily generated at -78° with LDA and reacts with electrophilic reagents RX to provide the corresponding addn. products and II in satisfactory to good yields. The a/g regioselectivity depends on the nature of the electrophile and is also discussed in comparison with the behavior of the anions of crotonamides.