Syntheses and reactions of multifunctional carbanions "ynolate anions"

Ynolates are carbanions having a triple bond in place of the double bond in enolate anions. Ynolates are ketene anion equivalents, thus ynolates introduce a ketene unit into substrates and the resulting products possess high reactivity. This allows ynolates to undergo unique reaction sequences. For the past 20 years, several methods for the generation of ynolates and their reactions have been developed. Recently, we have developed a highly efficient method for their generation and new rections such as olefination, tandem [2+2] cycloaddition-Dieckmann condensation, syntheses of β-lactams. In this review, an overview of the syntheses and the reactions of ynolates, especially focusing our recent results, are described.