Synthesis of 1,3,4-Trisubstituted Benzenes from Morita-Baylis-Hillman Adducts of α-Bromocinnamaldehyde via [5+1] Annulation Strategy
作者:Su Yeon Kim、Ko Hoon Kim、Jin Woo Lim、Jae Nyoung Kim
DOI:10.1002/bkcs.10577
日期:2015.12
important in organic synthesis. The Morita–Baylis–Hillman (MBH) adducts have been used as useful starting materials for this purpose. There have been reported numerous methods including [4+2] cycloaddition, 6π-electrocyclization, [3+3] annulation, and consecutive [3+1+2] annulation protocols. During our recent studies using the MBH adducts of cinnamaldehydes, we reasoned out that the synthesis of 1,3,4-trisubstituted
以区域选择性方式构建适当官能化的苯环在有机合成中很重要。Morita-Baylis-Hillman (MBH) 加合物已被用作用于此目的的有用起始材料。已经报道了许多方法,包括 [4+2] 环加成、6π-电环化、[3+3] 环化和连续 [3+1+2] 环化协议。在我们最近使用肉桂醛的 MBH 加合物的研究中,我们推断出 1,3,4-三取代苯 3 的合成可以通过 [5+1] 环化方案从 α-溴肉桂醛的 MBH 加合物的乙酸酯通过如方案 1 所示,伯硝基烷烃的顺序 SN20 反应、分子内 1,6 共轭加成和 HBr 和 HNO2 的消除。因此,起始材料 1a-d 由 α-溴肉桂醛制备,如方案 2 所示。MBH 反应在 1,4-二氮杂双环[2.2.2] 辛烷 (DABCO) 存在下进行,以良好至中等收率 (45–83%) 生成相应的 MBH 加合物,并且乙酰化后 (Ac2O/DMAP) 以良好的产率