Small-Ring Compounds. XLVI. Stabilized Cyclopropylcarbinyl Anions. A Retro Cyclopropylcarbinyl-Allylcarbinyl Rearrangement

Abstract

The cyclopropylcarbinyl anion is stabilized by a phenyl group attached to the carbinyl carbon toward ring opening, provided that potassium or sodium is the counterion. Replacement of potassium by lithium or magnesium in ether leads to immediate rearrangement and formation of the corresponding covalent allylcarbinyl organometallic compound. These rearrangements are reversible as can be demonstrated with diphenylcyclopropyl-carbinyllithium, which is stable in tetrahydrofuran but completely opened to y,y-diphenyllallylcarbinyllithium in diethyl ether. The retro rearrangement for this case can be achieved by simply adding tetrahydrofuran to the ether solution. The reaction of y,y-diphenylallylcarbinylmercuric bromide with potassium leads to ring closure with the formation of the corresponding cyclopropylcarbinylpotassium derivative.