Intramolekulare Cycloadditionen in der Reihe der Binaphthyle

Abstract

Intramolecular cyloadditions of binaphtyl compoundsThree new bridged ketones, 7,8 and 9, have been isolated in 44%, 3% and 19% yields respectively (Scheme 2) by heating 2,2′‐bis‐allyloxy‐1,1′‐binaphthyl (5) at 215° for 16 hours. These compounds could be epimerized about C(16) by bases, and in particular 9 yielded the new epimer 10. The structures of the alcohols obtained by reduction of the keto group are also given (Scheme 2). The constitution of all compounds was derived from spectroscopic data, chiefly from their 1H‐NMR, spectra (tab. 2, 3 and fig. 1). The assignments were based on the observed long‐range coupling constant between H(endo)‐C(16) and H(endo)‐C(5) in 7 and 10 and on the analysis of chemical shifts and coupling constants in both the ketones and their derivatives. Moreover, the structures of the compounds investigated have been proved by x‐ray analysis of ketone 8 (chap. 3, fig. 2). The thermal conversion of binaphthylether 5 to the bridged ketones proceeds via an intramolecular Diels‐Alder reaction, followed by Claisen rearrangement (Scheme 8). On heating, the bis‐beta‐methylallyl ether 20 yielded the ketone 21 and a small amount of the ether 23 (Schemes 5 and 7). Ether 23 and binaphthyl monoallyl ether 26 were converted thermally to the bridged ketones 31 (Scheme 7) and 27 (Scheme 6) respectively. In addition, 26 underwent an intramolecular ene‐reaction to give the spiroketone 28 (Schemes 6 and 9). The structures of these compounds were also established, mainly by analysis of their 1H‐NMR. spectra.