Exclusively endo-selective lewis acid-vatalyzed hetero diels-alder reactions of (E)-1-phenylsuifonyl-3-alken-2-ones with vinyl ethers
作者:Eiji Wada、Wen Pei、Hiroshi Yasuoka、Uchou Chin、Shuji Kanemasa
DOI:10.1016/0040-4020(95)00980-9
日期:1996.1
producing 2,4-cis-3,4-dihydro-2H- pyrans in excellent yields, the configuration at 3-position depending upon the stereochemistry of the starting vinyl ethers. Reductive ring opening reactions of the 3,4-dihydro-2H-pyran cycloadducts with Et3SiH/TiCl4 lead to 6-alkoxy-l-phenylsulfonyl-2-hexanones, and the sulfonyl-stabilized carbanions derived from the 3,4-dthydro-2H-pyran cycloadducts are alkylated
(ê)-1-苯磺酰基-3-链烯-2-酮作为新杂1,3-二烯经历平滑路易斯酸如催化量的存在ZnI于此使用乙烯基醚类狄尔斯-阿尔德反应2,铕( fod)3和TiCl 2(i- PrO)2。该反应是绝对内选的,以优异的产率产生2,4-顺-3,4-二氢-2 H-吡喃,其3-位的构型取决于起始乙烯基醚的立体化学。3,4-二氢-2 H-吡喃环加合物与Et 3 SiH / TiCl 4的还原性开环反应生成6-烷氧基-1-苯基磺酰基-2-己酮,然后对衍生自3,4-dthydro-2 H-吡喃环加合物的磺酰基稳定的碳负离子进行烷基化,然后进行还原性脱磺酰化反应,得到2,4,6-三取代的3 ,4-二氢-2 H-吡喃衍生物。