SYNTHESES OF SOME CHLORONORBORNANES . AN IMPROVED SYNTHESIS OF 1,4-DICHLORONORBORNANE

1,4,7,7-Tetrachloronorbornane (9), prepared by reduction of 1,2,3,4,7,7-hexachloronorbornene (2) with hydrogen over palladized charcoal, is conveniently further reduced to 1,4-dichloronorbornane (1) by the action of diphenyltin dihydride in diglyme at 110-120°. This represents an improved synthesis of 1 (54% over-all, compared with 22% over-all yield by Wilcox's published2 procedure). Partial reduction of 9 to 1,4,7-trichloronorbornane (10), uncontaminated by 1, has been effected by using lithium aluminum hydride-lithium hydride in refluxing tetrahydrofuran and by using tri-n-butyltin hydride in refluxing methylcyclohexane. The difference in appearance between the nmr spectrum of 9 in benzene and in pyridine is rationalized in terms of a specific solvation interaction between the substrate and the pyridine-ring nitrogen in the collision complex. The dipole moments of 1, 9, and 10 have been measured (1.32, 3.30, and 2.83 D, respectively). © 1969, American Chemical Society. All rights reserved.