Synthesis of 1,2-diaminotruxinic δ-cyclobutanes by BF<sub>3</sub>-controlled [2 + 2]-photocycloaddition of 5(4<i>H</i>)-oxazolones and stereoselective expansion of δ-cyclobutanes to give highly substituted pyrrolidine-2,5-dicarboxylates
作者:Sonia Sierra、Rosa López、Enrique Gómez-Bengoa、Larry R. Falvello、Esteban P. Urriolabeitia
DOI:10.1039/d3ob00284e
日期:——
(465 nm) in the presence of the photosensitizer [Ru(bpy)3](BF4)2 (2.5 mol%) and the Lewis acid BF3·OEt2 (2 equiv.) in deoxygenated methanol at room temperature affords the corresponding 1,2-diaminotruxinic cyclobutane bis-amino esters 2a–2u stereoselectively as the δ-isomer. Characterization of cyclobutanes 2 shows that the photocycloaddition takes place by the coupling of two Z-oxazolones in a head-to-head
在光敏剂 [ Ru ( bpy ) 3 ] (BF 4 ) 2 (2.5 mol% ) 存在下用蓝光 (465 nm) 照射 ( Z )-4-arylidene- 5(4 H ) -oxazolones 1a –1u ) 和路易斯酸 BF 3 ·OEt 2(2 当量)在室温下脱氧甲醇中得到相应的 1,2-二氨基环丁烷双氨基酯2a–2u立体选择性作为 δ 异构体。环丁烷2的表征表明,光环加成是通过两个Z-恶唑酮在头对头 1,2-反方式。BF 3添加剂的O-或/和N-键促进了偶联取向的这种变化。在存在 NaOMe(1/1 摩尔比)的情况下,在甲醇中加热时, δ-环丁烷2会发生扩环,以区域和立体选择性方式生成密集取代的吡咯烷-2,5-二羧酸盐3 。已经使用 DFT 方法阐明了环丁烷到吡咯烷扩环的机理。