Complete Control of Regioselectivity in the Intramolecular [2 + 2] Photocycloaddition of 2-Alkenyl-3(2<i>H</i>)-furanones by the Length of the Side Chain
作者:Thorsten Bach、Michael Kemmler、Eberhardt Herdtweck
DOI:10.1021/jo0264372
日期:2003.3.1
The 2-(omega-alkenyl)-substituted 2-methyl-3(2H)-furanones 2a and 2b were prepared from biacetyl (3) in four reaction steps and in overall yields of 20% and 21%, respectively. They underwent a clean intramolecular [2 + 2] photocycloaddition upon irradiation at lambda = 350 nm. Whereas compound 2a reacted in the expected manner and yielded 7-oxabicyclo[3.2.1.0(3,6)]octane 7 (87% yield), the regioselectivity
在四个反应步骤中,由联乙酰(3)制备2-(ω-烯基)-取代的2-甲基-3(2H)-呋喃酮2a和2b,总产率分别为20%和21%。他们在λ= 350 nm的辐射下进行了干净的分子内[2 + 2]光环加成反应。尽管化合物2a以预期的方式反应并产生了7-氧杂双环[3.2.1.0(3,6)]辛烷7(87%的产率),但是化合物2b的光环加成中的区域选择性被完全颠倒了。反应产生具有不寻常的9-氧杂双环[4.2.1.0(3,8)]壬烷骨架的化合物8(92%产率),其结构通过单晶X射线晶体学确定。