カチオン環化共2量化反応 : [3.n] シクロファン類の合成
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概要
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Divinyl monomers like 1, 3-bis (<I>p</I>-vinylphenyl) propane were treated by trifluoromethanesulfonic acid in dry benzene to generate cyclic cations which were trapped in situ by a comonomer and subsequently deprotonated to afford cyclocodimers or 1-methyl-3-styryl [3.n] cyclophanes (n>2). The process, so-called cationic cyclocodimerization, is reviewed here. Several cyclophanes such as [3.n] paracyclophane, [3.n] metacyclophane, [3. n] biphenylophane, [3. n] paracyclo (1.4) naphthalenophane, [3.n](1, 4)-, (1, 5)-, and (2, 6) naphthalenophane derivatives were prepared by this method. Syntheses of monomers, reaction conditions, comonomer properties, and its extension to cationic cyclization toward [3.n.3.n] paracyclophanes are outlined.<BR>Cyclophanes obtained can be converted easily to several cyclophanes possessing a functional group at a bridge. Using those cyclophane derivatives, acetolysis of cyclophanylmethyl tosylates and rearrangement of cyclophanylcarbenes were studied. The former showed the strong participation of neighboring [3.3] paracyclophanyl group, because the group has the highest electron donating nature among [n.m] paracyclophanes with the almost ideal structural environment for solvolysis. The latter showed the strain effect of [3.n] paracyclophanyl groups on the fates of the carbenes.<BR>Consequently, the cationic cyclocodimerization can give a series of [3.n] cyclophanes which are useful for systematic investigations of reaction intermediates with a stereochemical guide namely a methyl group at C-1 position.
- 社団法人 有機合成化学協会の論文