Allylindation of Cyclopropenes in Organic and Aqueous Media: Switching the Regio- and Stereoselectivity Based on the Chelation with a Hydroxyl Group and the Crystal Structure of the Cyclopropylindium Product

Hydroxy‐bearing cyclopropenes react with allylindium reagents to undergo clean allylindation both in organic and aqueous media, in which the chelation of the hydroxyl group to indium plays the central role. The regio‐ and stereoselectivity have been regulated both by the location of the hydroxyl group in the molecules and the reaction solvents. In particular, the allylindation in water shows marked differences from that in organic solvents; the regio‐ and stereoselectivity have totally been reversed compared with those in organic solvents. Unusually stable cyclopropylindium compounds have been isolated from the reaction of 1‐(ω‐hydroxyalkyl)cyclopropenes and the structure has fully been established by X‐ray crystallography. Simply by changing organic solvents to water, the regio‐ and stereoselectivity in the allylindation of hydroxy‐bearing cyclopropenes (see scheme) have been totally reversed. The selectivities can also be switched by changing the location or protection of the hydroxyl groups.