Alkynyl hydrazones are synthesized conveniently from 2-oxo-3-butynoates and hydrazine by suppressing the susceptible formation of pyrazoles. The resultant hydrazones are transformed into alkynyl diazoacetates under metal-free and mild oxidative conditions in excellent yields. Further, the alkynyl cyclopropane and propargyl silane carboxylates are synthesized in good yields by developing an unprecedented copper-catalyzed alkynyl carbene transfer reaction.

Asymmetric organocatalytic reactions of various electron-deficient racemic allenes with a wide variety of nucleophiles and electrophiles were reviewed. The literature on enantioselective functionalization of allenes that employs chiral phosphine, amine, phase transfer, bifunctional, and Brønsted acid catalysis is presented along with the mecha-nisms. In addition, the review emphasizes methods of obtaining enantioenriched allenes from racemic allenes via organocatalytic (dynamic) kinetic resolution techniques. The synthetic utility of the developed methodologies toward the target-orientated biologically active molecules is narrated along with the examples.