Carbonates, allylic, coupling enol, alkylation

The more reactive ft -carbon atom of ketone a,/ -dianions can be regiospecifically coupled with alkyl halides to give first lithium enolates, which are then trapped by more reactive carbon electrophiles such as allylic halides. The first example shown in Table 8 deals with the sequential /1-alkylation and ce-allylation of a ketone a,/1-dianion1 13. Thus, the dianion underwent regioselective alkylation at the ft carbon with //-pentyl bromide and then allylation with allyl bromide at the a carbon. When an excess of allyl bromide is reacted with the a, ft -dianion, the diallylated product is obtained in a good yield, whereas a threefold excess of pentyl bromide only resulted in the formation of the ft-alkylation product. Similar consecutive alkyl/allyl-type reactions are also possible for ketone a,5-dianions14. 

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