作者:A. Köver、H.M.R. Hoffmann
DOI:10.1016/s0040-4020(01)86211-6
日期:——
respectively. Pinofuran (1) also reacted with allyl cations, giving [4+3] cycloadducts 19 and 20. All cycloadditions were π-facially selective, attack occurring exclusively from the face anti to the gem-dimethyl grouping. Further, in the case of cycloadduct 19, extended attack was slightly preferred over compact attack (19ββ : 19αα = 3:2) (α, β, refer to the tetrahydropyranone moiety).
应变pinofuran(合成1)和methylpinofuran(2)通过许多方法分析。通往1的优选途径是通过单保护的(Z)-烯二醇8,其通过Z-选择性LiNEt 2诱导的衍生自被保护的均烯丙基醇3(nopol )的环氧化物而获得。由1,4-二酮14制备甲基呋喃呋喃(2),其是通过将乙烯基格里纳德1,4-加成到品醋丙酮(12)中,然后进行臭氧分解而获得的。吡喃呋喃1和2与乙炔二羧酸二甲酯进入Diels-Alder加成反应,分别得到15和16。吡呋喃(1)也与烯丙基阳离子反应,得到[4 + 3]环加合物19和20。所有的环加成都是π面选择性的,仅发生在反面与宝石-二甲基基团发生的结合。此外,在环加成的情况下19,延长攻击被略微优于紧凑攻击(19ββ:19 αα= 3:2)(α,β,请参阅四氢吡喃酮部分)。