DEMONSTRATION OF A STABILIZED PYRAMIDAL NITROGEN (SP(3)) IN AN ACYCLIC SYSTEM BY H-1-NMR-SPECTROSCOPY - A STRONG REPULSIVE INTERACTION BETWEEN THE LONE ELECTRON-PAIR AND A PHENYL RING

Condensation of butanone-2 and 4-methylpentanone-2 with -(9',10'-dihyd roanthracene-9',10'-diyl)succinimide gives only one isomeric form of h ydrazones which are assigned E-configuration. With an excess of sodium borohydride in methanol, one of the carbonyls of the hydrazone is red uced to -CHOH and the -N = CCH3R is transformed into -NH-CHCH3R. Highl y shielded N'-alkyl protons in H-1 NMR indicate that N'-alkyls are rig ht over the cage phenyl ring, which would result from the non-invertin g pyramidal geometry of the exocyclic nitrogen. A strong repulsion bet ween the lone electron pair of Nsp(3)- and the pi-electrons of the phe nyl ring has been attributed to the restricted inversion of pyramidal nitrogen. Diastereomeric nature of the methyl protons indicates two co nformations about Nsp(3)-Csp(3) bond which have been shown in the popu lation ratio of 1:2. The -OH group of the pyrrolidine ring has been pr oposed to be exo-to the cage. 5-Acetoxy-N'-acetyl, derivative exhibits restricted relation about the N-N bond and a preferred conformation w ith the N'-alkyl in syn-orientation, which supports the proposed stere ochemistry of the -OH group.