3-aza[5]metacyclophanes: Synthesis and reactions

The synthesis of the dichloro substituted 3-aza[5]metacyclophane (6b) has b een achieved starting from the N-tosyl derivative (7) by a four-step proced ure consisting of dichlorocarbene addition, flash vacuum thermolysis, a sec ond dichlorocarbene addition, and base catalyzed elimination; similarly, th e monochloro analogue (6c) was prepared. Their structure was confirmed by X -Ray crystal structure determination which indicated that the deformation o f their benzene rings was only slightly stronger than that of the carbon an alogue 8,11-dichloro[5]metacyclophane (15b). H-1 NMR spectroscopy showed th at in solution, like in the crystal, both 6b and 6c occurred in the exo con formation exclusively. Contrary to expectation, the reactivity of 6b and 6c towards several dienophiles was clearly higher than that of 15b. Thermally , 6b was converted to the 1,2,4,5-tetrahydropyrrolo[3,2, 1-hi]indole (23b) by a remarkable intramolecular nucleophilic attack of the tosylamide nitrog en on the benzene ring.