SMALL RING SYSTEMS FORM ISOCYANIDES .I. REACTION OF ISOCYANIDES WITH HEXAFLUOROBUTYNE-2

The use of the characteristic α,α-addition reaction of isocyanides as a method for the formation of a small membered ring system has been investigated. In inert solvents, isocyanides react with 2 mol of hexafluorobutyne-2 to produce cyclopropenylketenimine derivatives. None of the simple 1:1 adducts (the anticipated imino-cyclopenone derivatives) were detected. The cyclopropenylketenimines were easily hydrolyzed to the corresponding cyclopropenylamides and reduced to cyclopropane derivatives. When isocyanides were allowed to react with hexafluorobutyne-2 in ethanol as solvent, two different 1:1:1 adducts (isocyanide: butyne: ethanol) were obtained, a ketenimine and a conjugated imino ester. The structure of these 1:1:1 adducts imply the prior formation of a 1:1 intermediate that may have predominant carbene or carbanion character. © 1969, American Chemical Society. All rights reserved.