炔醛参与的直接Mannich反应*
2013-03-26黄涌澜董理进卢晓霞
黄涌澜,董理进,王 超,卢晓霞,孙 健
(1.中国科学院成都生物研究所天然产物研究中心,四川成都 610041;2.中国科学院大学,北京 100049)
Mannich反应是一类重要的常规有机反应,在形成C-C键的同时形成C-N键,可方便合成β-氨基羰基类化合物,如 β-氨基酮、酸及酯[1,2]。这些产物是重要的有机合成中间体,广泛应用于材料化学[3,4]和药物化学[5,6]等领域。
直接Mannich反应通常以酮作为亲核试剂即Mannich供体,以醛和胺原位反应生成的亚胺作为亲电试剂即Mannich受体。过去几十年来,已发展出了多种类型的Mannich供体[7],但能直接用于Mannich反应的受体却基本局限于芳香醛及脂肪醛与胺形成的亚胺[8]。α,β-不饱和醛由于易与胺发生Michael加成而极少用于α,β-不饱和醛的Mannich受体。目前,仅有几例α,β-不饱和醛参与的直接Mannich反应的文献报道[9~11],而炔醛参与的直接Mannich反应目前尚未见文献报道。
本文首次报道了在布朗斯特酸催化下,芳基炔醛参与的直接Mannich反应,较高收率地合成了一系列新型的含有炔基的β-氨基酮化合物(4a~4g)。最佳反应条件为:以乙酸(0.08 mmol)为催化剂,THF(2 mL)为溶剂,芳基炔醛(1a~1c,0.4 mmol),脂肪胺(2a,2d,2e,0.8 mmol)与酮(3a,3f,3g,0.8 mmol)于室温反应48 h,4a~4g收率68% ~89%。
Scheme 1
1 实验部分
1.1 仪器与试剂
Avance Brucker-600 MHz 型 核 磁 共 振 仪(CDCl3为溶剂,TMS为内标);Bio ToF-Q型高分辨质谱仪。
HSGF254型薄层板硅胶,200目~300目,青岛海洋化工厂;其余所用试剂均为分析纯。
1.2 4 的合成(以4a)为例
在厚壁试管中加入苯基丙炔醛(1a)52 mg(0.4 mmol)和 THF 2 mL,搅拌使其溶解;依次加入醋酸4.8 μL(0.08 mmol),苄胺(2a)88 μL(0.8 mmol)及甲基异丙基酮(3a)96 μL(0.8 mmol),于室温反应48 h。减压浓缩后经硅胶柱层析[洗脱剂:V(石油醚)∶V(乙酸乙酯)=15∶1]纯化得4a。用类似方法合成4b~4g。
4a:淡黄色固体,收率 85%;1H NMR δ:7.36~ 7.38(m,2H),7.22 ~ 7.28(m,7H),7.18(t,J=7.2 Hz,1H),4.00(d,J=12.9 Hz,1H),3.76(d,J=13.0 Hz,1H),3.70(s,1H),2.00(s,3H),1.19(s,3H),1.16(s,3H);13C NMR δ:211.72,139.63,131.75,128.68,128.36,128.33,128.23,127.18,123.12,88.08,85.63,56.67,52.09,51.92,25.35,23.35,19.04;HR-MS(ESI):Calcd for C21H23NONa{[M+Na]+}328.167 2,found 328.167 8。
4b:淡黄色液体,收率 76%;1H NMR δ:7.38(s,1H),7.30 ~ 7.35(m,4H),7.25(d,J=6.8 Hz,1H),6.57(d,J=3.0 Hz,1H),6.40(s,1H),4.05(d,J=13.0 Hz,1H),3.78 ~3.82(m,2H),2.07(s,3H),1.26(s,3H),1.22(s,3H);13C NMR δ:211.42,143.29,139.40,136.83,128.66,128.30,127.19,114.86,110.82,92.49,75.84,56.78,52.02,51.76,25.31,23.33,19.07;HR-MS(ESI):Calcd for C19H21NO2Na{[M+Na]+}318.147 0,found 318.147 8。
4c:白色固体,收率 89%;1H NMR δ:7.36(d,J=7.4 Hz,2H),7.32(t,J=7.4 Hz,2H),7.25(d,J=7.0 Hz,1H),7.04(d,J=8.2 Hz,1H),6.93(s,1H),6.81(d,J=8.3 Hz,1H),4.08(d,J=13.0 Hz,1H),3.90(s,6H),3.83(d,J=13.0 Hz,1H),3.77(s,1H),2.08(s,3H),1.27(s,3H),1.24(s,3H);13C NMR δ:211.82,149.38,148.59,139.59,128.58,128.23,127.07,124.96,115.20,114.32,110.96,86.31,85.43,56.60,55.90,55.88,52.01,51.90,25.27,23.29,18.93;HR-MS(ESI):Calcd for C23H27NO3Na{[M+Na]+}388.188 9,found 388.189 6。
4d:淡黄色液体,收率 79%;1H NMR δ:7.01(d,J=8.2 Hz,1H),6.90(s,1H),6.79(d,J=8.3 Hz,1H),3.88(s,6H),3.78(s,1H),2.94(m,1H),2.55(dd,J=11.4 Hz,7.0 Hz,1H),2.19(s,3H),1.35 ~1.41(m,4H),1.32(s,3H),1.24(s,3H),0.91(t,J=9.0 Hz,3H);13C NMR δ:212.05,149.40,148.67,124.93,115.43,114.44,111.06,87.00,84.97,57.73,55.93,51.99,48.25,32.01,25.54,23.29,20.43,19.00,13.95;HR-MS(ESI):Calcd for C20H29NO3Na{[M+Na]+}354.2045,found 354.204 8。
4e:淡黄色固体,收率 67%;1H NMR δ:7.02(d,J=8.2 Hz,1H),6.90(s,1H),6.79(d,J=8.3 Hz,1H),5.90 ~ 5.83(m,1H),5.23(d,J=17.1 Hz,1H),5.11(d,J=10.2 Hz,1H),3.88(s,6H),3.81(s,1H),3.53(m,1H),3.28(m,1H),2.18(s,3H),1.27(s,3H),1.25(s,3H);13C NMR δ:211.95,149.36,148.59,136.36,129.96,124.92,116.57,115.23,114.30,110.95,86.46,85.24,56.60,55.89,51.88,50.74,29.66,25.54,23.27,19.07;HR-MS(ESI):Calcd for C19H25NO3Na{[M+Na+}338.173 2,found 338.173 7。
4f:淡黄色固体,收率 84%,d/r=3/4;1H NMR δ:7.41(d,J=7.51 Hz,1H),7.24 ~7.36(m,3H),7.01,7.06(d,J=8.3 Hz,1H),6.90,6.94(s,1H),6.79,6.81(d,J=8.3 Hz,2H),4.08,4.13(d,J=13.1 Hz,1H),3.88,3.90(s,6H),3.79,3.97(s,1H),1.50 ~2.39(m,8H),1.22,1.27(s,3H);13C NMR δ:213.67,214.19,149.34,149.47,148.62,148.70,139.72,140.32,128.43,128.65,128.26,126.91,127.09,125.02,125.08,115.40,115.56,114.52,111.02,112.09,86.05,86.68,85.42,85.59,55.97,54.04,55.31,52.97,53.21,51.76,52.30,38.68,39.28,34.62,37.89,26.58,27.72,21.02,20.92,20.95,18.55;HR-MS(ESI):Calcd for C25H29NO3Na{[M+Na]+}414.204 5,found 414.204 0。
4g:淡黄色固体,收率68%,d/r=21/1;1H NMR δ:7.38(d,J=7.5 Hz,2H),7.32(t,J=7.5 Hz,2H),7.24(d,J=7.2 Hz,1H),7.01(dd,J=8.3 Hz,1.7 Hz,1H),6.90(d,J=1.6 Hz,1H),6.79(d,J=8.3 Hz,1H),4.11(d,J=13.3 Hz,1H),3.88(d,J=1.2 Hz,6H),3.85(d,J=13.3 Hz,1H),3.63(s,1H),2.34 ~2.35(m,2H),2.31(m,1H),2.22(m,1H),2.00(m,1H),1.80(m 2H),1.22(s,3H);13C NMR δ:221.62,149.44,148.65,139.99,128.34,127.01,124.98,115.31,114.50,111.03,87.01,85.09,55.98,55.93,54.93,52.95,51.85,38.40,33.21,29.69,19.54,18.93;HR-MS(ESI):Calcd for C24H27NO3Na{[M+Na]+}400.188 9,found 400.188 7。
2 结果与讨论
2.1 反应条件优化
以合成4a为模板,考察催化剂和溶剂对反应的影响,寻找最佳反应条件。
1a 0.4 mmol,2a 0.8 mmol,3a 0.8 mmol,其余反应条件同1.2,考察催化剂和溶剂对反应的影响,结果见表1。从表1可见,乙酸的催化效果最佳(Entry 8~Entry 13),收率达85%(Entry 8)。从表1还可见,以乙酸为催化剂时,溶剂对反应的影响较大(Entry 1~Entry 8),除 1,4-二氧六环,DMF和甲苯能获得中等收率外,其余溶剂反应收率均很低(Entry 1~Entry 4),最佳溶剂为THF。
表1 催化剂和溶剂对合成4a收率的影响*Table 1 Effect of catalyst and solvent on synthesizing 4a
2.2 扩展底物
在最优条件下,对底物进行拓展,合成了4b~4g。由此可见,在乙酸催化下,1a,呋喃丙炔醛(1b)和3,4-二甲氧基苯基丙炔醛(1c)均能顺利与2a和3a发生Mannich反应,获得较高收率的产物。除了3a外,2-甲基环己酮(3f)也能参与反应获得不错的收率,产物4f为非对映异构体,其d/r=3/4。有趣的是,2-甲基环戊酮(3g)参与同样的反应,获得了高达20/1的非对映异构体比例(d/r=20/1)。此外,除了苄胺之外,其他脂肪胺如正丁胺和烯丙胺也能获得不错的收率。
3 结论
首次报道了炔醛参与的直接Mannich反应。在乙酸催化下,芳基丙炔醛与几种酮和脂肪胺反应生成了含炔基的β-氨基酮新化合物。该反应条件温和,操作简单,收率良好,不仅为含炔基β-氨基酮类化合物的合成提供了便利的途径,也为进一步实现炔醛的不对称Mannich反应奠定了良好的基础。
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