新型螺环氧化吲哚曲酸衍生物的简便合成*

2014-06-23 16:22张庆王继宇陈俐娟张晓梅
合成化学 2014年3期
关键词:淡黄色吲哚纯度

张庆,王继宇,陈俐娟,张晓梅

(1.四川大学生物治疗国家重点实验室,四川成都 610041; 2.中国科学院成都有机化学研究所,四川成都 610041)

新型螺环氧化吲哚曲酸衍生物的简便合成*

张庆1,2,王继宇2,陈俐娟1,张晓梅2

(1.四川大学生物治疗国家重点实验室,四川成都 610041; 2.中国科学院成都有机化学研究所,四川成都 610041)

曲酸、靛红和氰基乙酸甲酯在碳酸氢钠催化下经三组分缩合反应合成了一系列新型的3,3'-螺环氧化吲哚曲酸衍生物,其结构经1H NMR,13C NMR和ESI-HR-MS表征。在最佳反应条件[甲醇为溶剂,1 eq.碳酸氢钠为催化剂,于室温反应24 h]下,收率最高为86%。

曲酸;靛红;螺环氧化吲哚;串联反应;合成

近年来,螺环氧化吲哚的合成引起了研究人员的兴趣,已有大量文献[1-11]报道采用不同方法合成一系列螺环氧化吲哚类化合物。

曲酸(1)5-位羟基具有弱酸性,能够与许多金属成盐,可以作为一种金属离子指示剂。通过对1的衍生,可以得到结构性能较稳定的曲酸衍生物,它们是大量天然产物及类似物的重要构建部分[12-14]。

本文首次报道在碳酸氢钠催化下,1,靛红衍生物(2a~2o)和氰基乙酸甲酯(3)在甲醇中经三组分缩合反应合成了一系列新型的螺环氧化吲哚曲酸衍生物(4a~4o,Scheme 1),其结构经1H NMR,13C NMR和ESI-HR-MS表征。并对反应条件进行了优化。在最佳反应条件[甲醇为溶剂,1 eq.碳酸氢钠为催化剂,于室温反应24 h]下,收率最高为86%。

1 实验部分

1.1 仪器与试剂

Buchi Melting Point B-545型电热数字显示熔点仪(温度未校正);Bruker-300型核磁共振仪(DMSO-d6为溶剂,TMS为内标);BrukerBioToF-Q型高分辨质谱仪;Water 2487型高效液相色谱仪[C-18柱,流动相:MeCN/0.1 mol·L-1H3PO4= 20/80~50/50,λ=254 nm]。

1,阿拉丁试剂有限公司;2a~2o和3,爱斯特医药技术有限公司;柱层析硅胶(200目~300 目)和薄层层析硅胶板,青岛海洋化工厂;其余所用试剂均为分析纯。

1.2 4合成(以4a为例)

在厚壁试管中依次加入1 42.6 mg(0.3 mmol),靛红(2a)44.1 mg(0.3 mmol),3 29.7 mg (0.3 mmol),NaHCO325.2 mg(0.3 mmol)和甲醇5 mL,搅拌下于室温反应24 h(TLC监测)。浓缩后经硅胶柱层析[洗脱剂:V(二氯甲烷)∶V(甲醇)=25∶1→15∶1→10∶1]纯化得4a。

用类似方法合成4b~4o。

4 a:淡黄色固体,收率85%,纯度98.83%,m.p.304℃~305℃;1H NMR δ:10.60(s,1H),8.03(s,2H),7.23~7.17(m,1H),7.10 (d,J=7.26 Hz,1H),6.92(d,J=7.47 Hz,1H),6.86(t,J=5.7 Hz,1H),6.32(s,1H),5.61(t,J=6.12 Hz,1H),4.08(dd,J=15.78 Hz,5.70 Hz,1H),3.97(dd,J=15.81 Hz,5.91 Hz,1H),3.29(s,3H);13C NMR δ: 177.1,169.4,168.3,167.1,159.8,147.9,142.4,136.4,133.5,128.9,123.4,122.0,111.4,109.4,73.8,59.0,50.5;HR-ESI-MS m/z:Calcd for C18H14N2O7Na{[M+Na]+}: 393.069 9,found 393.070 2。

4 b:淡黄色固体,收率65%,纯度98.82%,m.p.261℃~262℃;1H NMR δ:8.09(s,2H), 7.34~7.28(m,1H),7.22(d,J=7.32 Hz,1H),7.13(d,J=7.74 Hz,1H),7.04(t,J= 7.47 Hz,1H),6.33(s,1H),5.60(t,J=6.15 Hz,1H),5.18(d,J=10.98 Hz,1H),5.12(d,J=11.01 Hz,1H),4.04(dd,J=16.02 Hz,6.12 Hz,1H),3.95(dd,J=15.69 Hz,6.06 Hz,1H),3.33(s,3H),3.27(s,3H);13C NMR δ:176.2,169.3,168.3,166.9,159.8,147.2,142.2,136.4,132.1,129.0,123.4,123.2,111.5,109.3,73.5,71.4,58.9,55.8,50.6; HR-ESI-MS m/z:Calcd for C20H18N2O8Na{[M+ Na]+}437.096 1,found 437.095 9。

4 c:淡黄色固体,收率86%,纯度99.1%,m.p.283℃~284℃;1H NMR δ:8.10(s,2H),7.30(t,J=7.71 Hz,1H),7.17(d,J=7.20 Hz,1H),7.10(d,J=7.62 Hz,1H),6.98(t,J= 7.44 Hz,1H),6.31(s,1H),5.59(t,J=6.18 Hz,1H),4.04(dd,J=15.87 Hz,6.15 Hz,1H),3.93(dd,J=15.63 Hz,5.91 Hz,1H),3.80~3.70(m,2H),3.24(s,3H),1.19(t,J=7.05 Hz,3H);13C NMR δ:174.9,169.3,168.2,167.0,159.9,147.6,142.6,136.3,132.8,128.9,123.2,122.4,111.3,108.3,73.3,58.9,50.4,34.5,12.1;HR-ESI-MS m/z: Calcd for C20H18N2O7Na{[M+Na]+}421.101 2,found 421.101 2。

4 d:白色固体,收率73%,纯度99.18%,m.p.275℃~276℃;1H NMR δ:8.11(s,2H),7.45~7.30(m,5H),7.25~7.19(m,2H),7.00~6.93(m,2H),6.34(s,1H),5.64(t,J=6.03 Hz,1H),5.10(d,J=15.75 Hz,1H),4.82(d,J=15.81 Hz,1H),4.04(dd,J=16.41 Hz,6.33 Hz,1H),3.94(dd,J=15.90 Hz,5.85 Hz,1H),3.18(s,3H);13C NMR δ:175.6,169.3,168.4,167.0,159.9,147.5,142.8,136.5,136.4,132.6,129.0,128.6,127.4,127.3,123.4,122.8,111.4,108.9,73.4,58.9,50.6,43.3;HR-ESI-MS m/z:Calcd for C25H20N2O7Na{[M+Na]+}483.116 8,found 483.116 8。

4 e:淡黄色固体,收率56%,纯度99.01%,m.p.271℃~272℃;1H NMR δ:8.14(s,2H),7.61(t,J=7.35 Hz,2H),7.51(d,J=7.29 Hz,1H),7.46~7.43(m,2H),7.27(d,J=7.14 Hz,1H),7.24(d,J=6.22 Hz,1H),7.04(t,J=7.57 Hz,1H),6.71(d,J=7.85 Hz,1H),6.35(s,1H),5.63(t,J=6.14 Hz,1H),4.16 (dd,J=15.99 Hz,6.21 Hz,1H),4.54(dd,J= 15.78 Hz,5.94 Hz,1H),3.38(s,3H);13C NMR δ:175.0,169.4,168.3,167.0,160.0,147.5,143.4,136.4,134.4,132.3,129.8,129.1,128.3,126.7,123.8,123.3,111.5,108.8,73.4,59.1,50.8;HR-ESI-MS m/z:Calcd for C24H18N2O7Na{[M+Na]+} 469.101 2,found 469.100 7。

4 f:淡黄色固体,收率66%,纯度99.58%,m.p.284℃~285℃;1H NMR δ:8.06(s,2H),7.31(t,J=7.77 Hz,1H),7.17(d,J=7.11 Hz,1H),7.06(d,J=7.74 Hz,1H),6.99(t,J= 7.29 Hz,1H),6.32(s,1H),5.59(t,J=6.00 Hz,1H),4.06(dd,J=15.57 Hz,6.06 Hz,1H),3.94(dd,J=15.60 Hz,6.00 Hz,1H),3.26(s,3H),3.21(s,3H);13C NMR δ:175.6,169.3,168.3,167.0,159.8,147.5,143.9,136.5,132.7,129.0,123.1,122.6,111.4,108.3,73.7,58.9,50.7,26.7;HR-ESI-MS m/z: Calcd for C19H16N2O7Na{[M+Na]+}407.085 5,found 407.085 6。

4 g:白色固体,收率73%,纯度99.09%,m.p.275℃~276℃;1H NMR δ:7.51(brs,1H),7.23~7.18(m,1H),7.02(d,J=6.37 Hz,1H),6.98~6.93(m,1H),6.80(d,J= 7.81 Hz,1H),6.40(s,1H),5.87~5.76(m,1H),5.30~5.19(m,2H),4.48~4.41(m,1H),4.24~4.17(m,1H),4.10(d,J=16.04 Hz,1H),4.01(d,J=16.85 Hz,1H),3.29(s,3H);13C NMR δ:176.1,171.3,169.0,167.5,160.0,148.3,142.4,136.9,132.5,130.9,129.1,123.4,123.1,117.6,111.3,108.9,74.1,59.5,50.77,42.8,29.5;HR-ESI-MS m/z:Calcd for C21H18N2O7Na{[M+Na]+} 433.101 2,found 433.101 0。

4 h:淡黄色固体,收率84%,纯度99.19%,m.p.281℃~282℃;1H NMR δ:10.62(s,1H),8.06(s,2H),7.14~7.10(m,1H),7.05~6.98(m,1H),6.85~6.81(m,1H),6.32(s,1H),5.60(t,J=6.12 Hz,1H),4.11~4.00(m,2H),3.30(s,3H);13C NMR δ: 177.2,169.4,168.3,167.1,159.8,158.1(d,J=235.9 Hz,1C),147.2,138.6,136.5,135.1 (d,J=7.7 Hz,1C),115.1(d,J=23.1 Hz,1C),111.6(d,J=24.8 Hz,1C),111.5,110.0 (d,J=8.0 Hz,1C),73.5,59.0,50.5;HRESI-MS m/z:Calcd for C18H13N2O7FNa{[M+ Na]+}411.060 4,found 411.060 1。

4 i:淡黄色固体,收率64%,纯度99.53%,m.p.294℃~295℃;1H NMR δ:8.10(s,2H),7.24~7.20(m,1H),7.18~7.11(m,1H),7.09~7.05(m,1H),6.33(s,1H),5.60(t,J=6.21 Hz,1H),4.06(dd,J=15.96 Hz,6.12 Hz,1H),3.96(dd,J=15.75 Hz,6.15 Hz,1H),3.28(s,3H),3.20(s,3H);13C NMR δ: 175.6,169.4,168.3,166.9,159.8,158.6(d,J=236.6 Hz,1C),146.8,140.2,136.7,134.3 (d,J=7.8 Hz,1C),115.1(d,J=23.1 Hz,1C),111.6(d,J=21.2 Hz,1C),111.4,109.2 (d,J=8.1 Hz,1C),73.4,59.0,50.7,26.9; HR-ESI-MS m/z:Calcd for C19H15N2O7FNa{[M+ Na]+}425.076 1,found 425.076 0。

4 j:淡黄色固体,收率71%,纯度99.43%,m.p.291℃~292℃;1H NMR δ:7.13~7.09 (m,1H),6.95(d,J=1.95 Hz,1H),6.76(d,J=8.22 Hz,1H),6.40(s,1H),4.14(d,J= 16.32 Hz,1H),4.05(d,J=16.23 Hz,1H),3.34(s,3H);13C NMR δ:171.3,169.0,139.9,136.9,134.8,129.0,127.9,124.0,111.4,110.7,73.4,59.6,50.7;HR-ESI-MS m/z: Calcd for C18H13N2O7ClNa{[M+Na]+}427.030 9,found 427.031 6。

4 k:淡黄色固体,收率70%,纯度99.75%,m.p.298℃~299℃;1H NMR δ:10.75(s,1H),8.08(s,2H),7.39~7.36(m,2H),6.84~6.81 (m,1H),6.33(s,1H),5.61(t,J=6.09 Hz,1H),4.09(dd,J=15.69 Hz,5.88 Hz,1H),4.00 (dd,J=15.84 Hz,6.06 Hz,1H),3.32(s,3H);13C NMR δ:176.8,169.4,168.3,166.9,159.9,147.0,141.8,136.6,135.7,131.6,126.5,113.5,111.5,111.3,73.4,59.0,50.6;HR-ESIMS m/z:Calcd for C18H13N2O7BrNa{[M+Na]+} 470.980 4,found 470.980 4。

4 l:白色固体,收率75%,纯度99.53%,m.p.304℃~305℃;1H NMR δ:10.49(s,1H),8.04(s,2H),6.99(d,J=7.77 Hz,1H),6.92(s,1H),6.74(d,J=7.80 Hz,1H),6.32 (s,1H),5.62(t,J=6.12 Hz,1H),4.08(dd,J=15.72 Hz,6.03 Hz,1H),3.98(dd,J= 15.81 Hz,5.76 Hz,1H),3.30(s,3H),2.19 (s,3H);13C NMR δ:177.0,169.4,168.3,167.2,159.8,148.1,139.9,136.3,133.6,130.7,129.1,124.0,111.4,109.1,73.9,59.1,50.5,20.6;HR-ESI-MS m/z:Calcd for C19H16N2O7Na{[M+Na]+}407.085 5,found 407.084 8。

4 m:淡黄色固体,收率74%,纯度97.74%,m.p.214℃~215℃;1H NMR δ:11.35(s,1H),8.21~8.18(m,1H),8.14(s,2H),7.07 (d,J=8.55 Hz,1H),6.33(s,1H),5.60(t,J=6.15 Hz,1H),4.08(dd,J=15.96 Hz,6.18 Hz,1H),3.99(dd,J=15.66 Hz,6.09 Hz,1H),3.32(s,3H);13C NMR δ:177.7,169.4,168.2,166.7,160.0,148.9,146.2,142.5,136.8,134.3,126.2,119.5,111.6,109.5,73.0,59.0,50.6;HR-ESI-MS m/z:Calcd for C18H13N3O9Na{[M+Na]+}438.054 9,found 438.055 2。

4 n:淡黄色固体,收率63%,纯度99.23%,m.p.293℃~294℃;1H NMR δ:10.79(s,1H),8.07(s,2H),7.17(d,J=7.92 Hz,1H),6.96~6.93(m,1H),6.87(d,J=1.74 Hz,1H),6.33(s,1H),5.62(t,J=6.15 Hz,1H),4.09(dd,J=15.81 Hz,6.18 Hz,1H),4.01 (dd,J=15.81 Hz,6.12 Hz,1H),3.32(s,3H);13C NMR δ:177.1,169.3,168.3,167.0, 159.8,147.2,143.9,136.5,132.9,132.3,125.0,121.7,111.5,109.4,73.4,59.0,50.6; HR-ESI-MS m/z:Calcd for C18H13N2O7ClNa{[M +Na]+}427.030 9,found 427.030 7。

4 o:淡黄色固体,收率66%,纯度98.13%,m.p.313℃~314℃;1H NMR δ:7.19~7.16 (m,1H),6.94~6.87(m,2H),6.43(s,1H),4.20(d,J=16.17 Hz,1H),4.10(d,J=16.05 Hz,1H),3.38(s,3H);13C NMR δ:171.2,169.1,169.1,167.5,159.9,147.7,139.0,136.8,134.5,129.1,123.6,121.9,114.9,111.4,73.5,59.6,50.7;HR-ESI-MS m/z: Calcd for C18H13N2O7ClNa{[M+Na]+}427.030 9,found 427.031 4。

2 结果与讨论

2.1 反应条件优化

以合成4a为模板反应,考察催化剂、溶剂和反应温度对反应的影响,寻找最佳反应条件,结果见表1。由表1可见,以MeOH为溶剂,于25℃反应24 h的条件下(No.1~No.12),最佳的催化剂为NaHCO3。以NaHCO3(1 eq.,No.12)为催化剂时,收率较高(85%)。因此,选择无机碱NaHCO3为催化剂;进一步考察溶剂对反应的影响(No.12~No. 21),当采用其他极性较弱溶剂时,1溶解度小,大部分不反应。溶解度高的乙醇为溶剂时,所得产物有两种,有30%发生了酯交换。催化剂用量对反应的影响(No.22~No.25)结果表明,当催化剂用量1.0 eq.时,反应效果较好,减少或增加催化量,收率均下降。随后,尝试升高反应温度以进一步提高收率。实验结果(No.26~No.27)表明,温度升高对收率无影响,反应液颜色加深,杂质增多,分离提纯难度加大,收率降低。

综上所述,合成4a的最佳反应条件为:甲醇为溶剂,1 eq.NaHCO3为催化剂,于室温反应24 h。

2.2 底物扩展

在最佳反应条件下,考察反应对底物的普适性,实验结果见表2。由表2可见,该反应有较好的底物适应性,靛红N上连有H或Et时收率较高(No.1和No.3),而连有MOM,甲基或烯丙基时收率中等(No.2,No.6和No.7)。当N上保护基为Ph和Bn时反应不能进行,但是催化剂为有机碱三乙胺时,收率分别为56%和73%。靛红的苯环上取代基不管是吸电子还是供电子,反应收率均为中等(No.8~No.15)。

表1 反应条件优化*Table 1Process optimization of reaction

2.3 反应历程

推测该反应历程为:靛红和氰基乙酸甲酯在碱的催化下发生Knoevenagel反应,然后再和曲酸发生Michael加成反应并进行分子内环化、互变异构得螺环化合物(Scheme 2)。

表2 底物扩展*Table 2Substrate scope of cascade reaction

有趣的是,当以苯环4-位取代的靛红(2p:4-Br 或2q:4-Cl)参与反应时,二者则分别与1发生了aldol反应,而3并未参与反应。分析认为,该反应体系中Knoevenagel反应和aldol反应是竞争反应,由于靛红4-位的取代基对相邻羰基有较大的位阻效应,从而导致1首先进攻羰基碳经aldol反应生成5p(Chart 1){淡黄色固体,收率71%,m.p.191℃~192℃;1H NMR δ:12.77~12.64(brm,1H),10.20(brs,1H),7.15~7.09(m,1H),7.04(d,J=7.89 Hz,1H),6.80(d,J=7.41 Hz,1H),6.09(s,1H),5.39(brs,1H),3.97(d,J=15 Hz,1H),3.90(d,J=14.97 Hz,1H);13C NMR δ: 180.5,178.0,163.0,156.5,144.2,141.4,131.0,130.9,125.3,119.7,108.9,107.9,81.3,59.6;HR-ESI-MS m/z:Calcd for C14H10NO6BrNa{[M+Na]+}389.958 9,found 389.959 4}和5q (Chart 1){淡黄色固体,收率84%,m.p.185℃~186℃;1H NMR δ:12.71(brt,J=5.09 Hz 1H),10.15(brs,1H),7.20(t,J=8.04 Hz,1H),6.89(d,J=8.16 Hz,1H),6.77(d,J=7.71 Hz,1H),6.09(s,1H),5.42(brt,J=7.29 Hz,1H),3.98(d,J=14.97 Hz,1H),3.90(d,J= 14.97 Hz,1H);13C NMR δ:180.6,178.0,163.1,156.4,144.1,141.6,131.0,130.8,129.5,122.3,108.5,107.9,80.6,59.6;HRESI-MS m/z:Calcd for C14H10NO6ClNa{[M+Na]+} 346.009 4,found 346.009 6}。

3 结论

首次报道碳酸氢钠催化曲酸、靛红及氰基乙酸甲酯在温和条件下经三组分一锅反应简便合成新型3,3-位螺环氧化吲哚类化合物,最高收率为86%。

该方法具有反应条件温和、操作简单、收率良好等优点。该研究结果为进一步合成氧化吲哚类化合物方法奠定了良好的基础。

[1]Chen M H,Pollard P P,Patchett A A,et al.Synthesis and biological activities of spiroheterocyclic growth hormone secretagogues[J].Bioorg Med Chem Lett,1999,9:1261-1266.

[2]Behera R K,Behera A K,Pradhan R,et al.Short synthesis of 3-prenylcounarins by an unusual prenylation[J].Synth Commun,2006,36:3729-3742.

[3]Abdel-Rahman A H,Keshk E M,Hanna M A,et al.Synthesis and evaluation of some new spiro indolinebased heterocycles as potentially active antimicrobial agents[J].Bioorg Med Chem,2004,12:2483-2488.

[4]Ding K,Lu Y,Nikolovska-Coleska Z,et al.Structure-based design of spiro-oxindoles as potent,specific small-molecule inhibitors of the MDM2-p53 interaction [J].J Med Chem,2006,49:3432-3435.

[5]Edmondson S,Danishefsky S J,Sepp-lorenzinol L,et al.Total synthesis of spirotryprostatin A,leading to the discovery of some biologically promising analogues [J].J Am Chem Soc,1999,121:2147-2155.

[6]Jiang X,Cao Y,Wang Y,et al.A unique approach to the concise synthesis of highly optically active spirooxazolines and the discovery of a more potent oxindoletype phytoalexin analogue[J].J Am Chem Soc,2010,132:15328-15333.

[7]Tan B,Candeias N R,Barbas C F.Core-structure-motivated design of a phosphine-catalyzed[3+2]cycloaddition reaction:Enantioselective syntheses of spirocyclopenteneoxindoles[J].J Am Chem Soc,2011,133:4672-4675.

[8]Han Y Y,Han W Y,Hou X,et al.FeCl3-catalyzed stereoselective construction of spirooxindole tetrahydroquinolines via tandem 1,5-hydride transfer/ring closure [J].Org Lett,2012,14:4054-4057.

[9]Chen W B,Pei Q L,Wu Z J,et al.Highly enantioselective construction of spiro[4H-pyran-3,3'-oxindoles]through a domino knoevenagel/michael/cyclization sequence catalyzed by cupreine[J].Org Lett,2010,12: 3132-3135.

[10]Liu X L,Han W Y,Zhang X M,et al.Highly efficient and stereocontrolled construction of 3,3'-pyrrolidonyl spirooxindoles via organocatalytic domino Michael/cyclization reaction[J].Org Lett,2013,15: 1246-1249.

[11]Liao Y H,Wu Z J,Han W Y,et al.Organocatalytic enantioselective stereoablative hydroxylation of 3-halooxindoles:An effective method for the construction of enantioenriched 3-substituted 3-hydroxy-2-oxindoles [J].Chemistry——A European Journal,2012,18: 8916-8920.

[12]P A Wender,F E McDonald.Studies on tumor promoters.9.A second-generation synthesis of phorbol [J].J Am Chem Soc,1990,112:4956-4958.

[13]P A Wender,J L Mascarenas.Studies on tumor promoters.11.A new[5+2]cycloaddition method and its application to the synthesis of BC ring precursors of phorboids[J].J Org Chem,1991,56:6267-6269.

[14]Wang J Y,Zhang Q,Zhang H,et al.Organocatalytic enantioselective Michael addition of a kojic acid derivative to nitro olefins[J].Org Biomol Chem,2012,10: 2950-2954.

Facile Synthesis of Spiro[4H-pyran-3,3'-oxindoles]
kojic Acid Derivatives

ZHANG Qing1,2,WANG Ji-yu2,CHEN Li-juan1,ZHANG Xiao-mei2

(1.State Key Laboratory of Biotherapy,Sichuan University,Chengdu 610041,China; 2.Chengdu Institute of Organic Chemistry,Chinese Academy of Sciences,Chengdu 610041,China)

A series of novel spiro[4H-pyran-3,3'-oxindoles]kojic acid derivatives were synthesized by three-component condensation of kojic acid,methyl cyanoacetate and isatins in the presence of sodium bicarbonate.The structures were characterized by1H NMR,13C NMR and ESI-HR-MS.Under the optimum reaction conditions at rt for 24 h using methanol as the solvent and NaHCO3(1 eq.)as the catalyst,the yield was up to 86%.

kojic acid;isatins;spirooxindoles;cascade reaction;synthesis

O621.3

A

1005-1511(2014)03-0335-06

2013-11-05;

2014-03-20

张庆(1980-),女,汉族,四川成都人,硕士研究生,助理研究员,主要从事有机合成研究。

张晓梅,博士,研究员,E-mail:xmzhang@cioc.ac.cn

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