[n]Metacyclophanes 2 (n = 8-15), [n.n]metacyclophanes 3 (n = 2,5-10), and [5.5.5]metacyclophane 4 were obtained by reacting dianion 1 from 2,6-dimethylanisole with alpha,omega-dihalides. The favored conformations of these cyclophanes were deduced from their NMR spectra and molecular mechanics calculations. An X-ray study showed dimeric cyclophane 3 (n = 9) to crystallize in essentially the conformation calculated to be of lowest energy. The methoxyl groups move through the large ring rapidly on the NMR time scale when the ring is larger than 18-membered for monomeric cyclophanes 2, 16- or 17-membered for dimeric cyclophanes 3, and in trimeric cyclophane 4 with its 24-membered ring.
Syntheses of cyclic diselenides through diselenolates and the following deselenation reactions by means of three ways were studied. The preparation of the cyclic diselenides in the presence of excess sodium borohydride gave thirty-eight diselenides containing diselena[3.3]cyclophanes and alicyclic diseleno compounds in high yields in addition to two triple-bridged selenacyclophanes. Photodeselenation
[2.2]Metacyclophanes(=MCPs) which carry hydroxy, methoxy or methyl group at the inner position exhibited a stronger reactivity toward diazonium salts than the corresponding phenol, anisole or toluene, respectively. Such a reactivity was also estimated in connection with the UV spectra of the azo benzene component.
Medium-Sized Cyclophanes. 43.<sup>1</sup> First Evidence for <i>anti</i>−<i>syn</i>-Ring Inversion under the Nitration of 5,13-Di-<i>tert</i>-butyl-8,16-dimethoxy[2.2]metacyclophane
Nitration of 5,13-di-tert-butyl-8,16-dimethoxy[2.2]MC (metacyclophane = MCP) (1) with various nitrating reagents led to ipso-nitration at the tert-butyl group to give 5-tert-butyl-8,16-dimethoxy-13-nitro[2.2]MCP (2), as well as the corresponding 8,16-epoxy[2.2]MCP (4) arising from intramolecular condensation reaction via anti-syn-ring inversion of the nitration intermediate. This novel intramolecular condensation reaction to afford 8,16-epoxy[2.2]MCP (4) was also observed in the presence of Nafion-H under chlorobenzene reflux. The mechanism of the ipso-nitration as well as the present novel intramolecular condensation reaction is also discussed.
BATES, ROBERT B.;GANGWAR, SANJEEV;KANE, VINAYAK V.;SUVANNACHUT, KESSARA;T+, J. ORG. CHEM., 56,(1991) N, C. 1696-1699
作者:BATES, ROBERT B.、GANGWAR, SANJEEV、KANE, VINAYAK V.、SUVANNACHUT, KESSARA、T+