Olefinic alkyllithiums deprotonation

Addition of alkyllithium to cyclobutanones and transmetallation with VO(OEt)Cl2 is considered to give a similar alkoxide intermediates, which are converted to either the y-chloroketones 239 or the olefinic ketone 240 depending on the substituent of cyclobutanones. Deprotonation of the cationic species, formed by further oxidation of the radical intermediate, leads to 240. The oxovanadium compound also induces tandem nucleophilic addition of silyl enol ethers and oxidative ring-opening transformation to produce 6-chloro-l,3-diketones and 2-tetrahydrofurylidene ketones. (Scheme 95)... 

Most, perhaps all, of the reactions that simple alkenes undergo are also available to allenes. By virtue of their strain and of the small steric requirement of the sp-hybrid-ized carbon atom, the reactions of allenes usually take place more easily than the corresponding reactions of olefins. Because the allenes can also be chiral, they offer opportunities for control of the reaction products that are not available to simple alkenes. Finally, some reaction pathways are unique to allenes. For example, deprotonation of allenes with alkyllithium reagents to form allenyl anions is a facile process that has no counterpart in simple alkenes. These concepts will be illustrated by the discussion of cyclization reactions of allenes that follows. 

---