A study of some-strained azabicyclic compounds & their rearrangement reactions.

The barriers to nitrogen inversion were determined for several l-methyl-2-azabicyclo [2.1.1] heptyl systems. The rearrangement chemistry of the N-chloro derivative was investigated. This underwent silver-ion catalysed solvolysis to afford 4-methoxymethyl-2-methyl-l-pyrroline and also rearranged in the presence of alumina with retention of chlorine to give 2-methyl-2-chloro-l-azabicyclo [2.1.1] hexane, a novel ring system. The hydrochloride salt of this chlorine-retaining product rearranged with aqueous base to afford 4-hydroxymethyl-2-methyl-l-pyrroline. A study of 1,2,3,4-tetrafluoro-9,10-dihydroanthracen- 9,10-imines showed that electronic influences exhibit subtle effects on the mode of kinetically-controlled chlorination at the 11-position and on the preferred orientation of the chlorine substituent under conditions of thermodynamic control. The influence of aryl substituents on the rate of aryl participation during silver-ion catalysed solvolysis was also investigated. The heterolytic rearrangement of 9-chloro-l, 4-dimethyl- 2,3-dihydronapthalen-1, 4-imines required the use of novel solvolytic conditions. Unlike their l,4-dihydro analogues, these preferred rearrangement to benzo (f)-5H-azepines which themselves underwent an extensive series of rearrangements. Investigation of 7-chloro-l,7-diazabicyclo [2.2.1] heptane provided evidence that the effect of raising the barrier to nitrogen inversion by electronegative substituents arose predominantly from lone pair - lone pair repulsions. The 15N NMR signals of a variety of systems containing the 7- azabicyclo [2.2.1] heptyl skeleton were observed downfield of the most shielded examples reported for several classes of amine. X-ray crystallographic studies of two 9-chloro-2,3- dihydronapthalen-1, 4-imines, each possessing a different stereochemistry at nitrogen, showed that the position of the chlorine atoms exerts influence on the structure of the remainder of the 7-azabicyclo [2.2.l] heptyl skeleton.