Allyl- and benzylindium reagents. Carboindation of carbon-carbon and carbon-nitrogen triple bonds

The reaction of unactivated simple terminal alkynes 1 with allylindiums in THF proceeded smoothly to give the corresponding allylation products 2 in g ood to high yields. This result is in marked contrast to that of the reacti on carried out in DMF, where the allylation of unactivated alkynes was very sluggish. The allylic group of the reagent was attached to the internal ca rbon of the triple. bond, and indium was attached to the less substituted t erminal carbon, except for the case of TMS substituted acetylenes 1j and 1k in which the allyl group went to the less substituted carbon of the triple band. The reaction of unactivated simple terminal and certain internal ace tylenes with benzylindium in THF proceeded smoothly to afford the correspon ding benzylation products 18 in good to high yields. The benzyl group was a ttached to the less substituted unhindered carbon of the triple bond, and i ndium was attached to the more sterically congested carbon. The reaction of activated nitriles 3 with allylindiums in THF at 70 degrees C gave the cor responding allylation-enamination products 4 in high to excellent yields. T his reaction provides a useful method for the synthesis of highly functiona lized enamines, which are not easily available via conventional methods. Th e mechanisms on the above three indation reactions are discussed.