6-溴-7-异丙基-1,10-二甲基-1,2,3,4-四氢蒽-1-羧酸的合成*
2013-03-26黄国保黄胜梅谢厚知潘英明王恒山
黄国保,雷 茜,黄胜梅,谢厚知,潘英明,王恒山
(广西师范大学化学化工学院药用资源化学与药物分子工程重点实验室,广西桂林 541004)
松香酸具有多个构型稳定且易改造的手性官能团,其衍生物已应用于催化[1,2]和手性分离[3,4]。近年来本课题组在松香基手性分离试剂的研制与开发利用方面都取得了较大进展[5~8]。最近我们发现松香异构化产物与α-(9-蒽基)-α-甲氧基乙酸和S-1-萘基甲氧基乙酸有很相似的手性骨架,因此该类松香异构化产物有很强的磁各向异性,有望提高手性选择的性能,预期其可能具有更高的NMR识别能力。
本文以脱氢松香酸(1)为原料,通过酯化、溴代、异构化、水解等反应合成了磁各向异性更强的6-溴-7-异丙基-1,10-二甲基-1,2,3,4-四氢蒽-1-羧酸(8,Scheme 1),其结构经1H NMR,13C NMR,MS和元素分析表征。8为新化合物。
1 实验部分
1.1 仪器与试剂
Scheme 1
WRS-1A型数字熔点仪(温度未校正);Perkin Elmer Model 341型旋光仪;AVANCE AV 500型超导核磁共振仪(CDCl3为溶剂,TMS为内标);BRUKER ESQUIRE HCT型质谱仪;Carlo Erba 1106型元素分析仪。
脱氢松香酸甲酯(2)[9],7-氧基脱氢松香酸甲酯 (3)[10]和 12-溴-7-羰基脱氢松香酸甲酯(4)[11]按文献方法合成;NBS,安耐吉化学试剂有限公司;CDCl3,硼氢化钠和氢氧化锂,百灵威化学试剂有限公司;工业一级松香和歧化松香,梧州松脂厂;其余所用试剂均为分析纯。
1.2 合成
(1)12-溴-7-羰基-5,8,11,13-松香四烯-18-羧酸甲酯(5)的合成
在反应瓶中加入 4 0.6 g(1.5 mmol),二氧化硒3 g(27 mmol),冰醋酸13 mL 和水 6.5 mL,搅拌至均匀,回流(135℃)反应10 h。冷却至室温,旋蒸脱溶,加入乙醚30 mL,过滤,滤液依次用5%碳酸钠溶液(20 mL)和饱和食盐水(20 mL)洗涤,无水硫酸钠干燥,浓缩后经硅胶柱层析[洗脱剂:A=V(石油醚)∶V(乙酸乙酯)=9∶1]纯化,甲醇重结晶得无色晶体 5 0.5 g,收率82.7%,m.p.76℃ ~78 ℃;1H NMR δ:1.27 ~1.32(dd,J=7.0 Hz,6H,16,17-H),1.56(s,3H,20-H),1.66(s,3H,19-H),1.94 ~ 2.00(m,2H,2-H),2.21 ~2.48(m,2H,3-H),2.93 ~2.96(m,2H,4-H),3.35 ~3.41(m,1H,15-H),3.74(s,3H,21-H),6.14(s,1H,8-H),7.71(s,1H,11-H),8.03(s,1H,14-H)。
(2)6-溴-7-异丙基-1,10-二甲基-1,2,3,4-四氢蒽-1-羧酸甲酯(7)的合成
在反应瓶中加入 5 0.7 g(1.7 mmol),七水合三氯化铈0.8 g(3 mmol),甲醇3.5 mL和四氢呋喃3.5 mL,搅拌至完全溶解;加入硼氢化钠80 mg(2 mmol),于室温反应15 min。加入乙醚20 mL,用饱和食盐水洗涤,无水硫酸钠干燥,减压蒸除溶剂得 12-溴-7-羟基-5,8,11,13-松香四烯-18-羧酸甲酯(6)粗品。加入无水二氯甲烷30 mL,冰浴下加入三氟化硼(0.68 g)的乙醚(1.2 mL)溶液,搅拌下于室温反应1 h。加入乙醚50 mL,依次用稀盐酸(30 mL)和饱和食盐水(30 mL)洗涤,无水硫酸钠干燥,旋蒸脱溶后经硅胶柱层析(洗脱剂:A=10∶1)反复纯化得黄色膏状物7 0.51 g,两步总产率 76.2%,m.p.102 ℃ ~103 ℃,[α]20D-23 °(c0.50,CHCl3);1H NMR δ:1.36 ~1.37(s,6H,16,17-H),1.66(s,3H,19-H),1.69(s,3H,20-H),1.90 ~2.20(m,4H,2,3-H),2.93 ~2.96(m,2H,4-H),3.45 ~3.51(m,1H,15-H),3.74(s,3H,21-H),7.56(s,1H,9-H),7.60(s,1H,8-H),8.25(s,1H,5-H)。
(3)8的合成
在反应瓶中加入7 0.8 g(2 mmol),混合溶剂[V(甲醇)∶V(四氢呋喃)∶V(水)=2 ∶2 ∶1]10 mL,搅拌使其完全溶解;加入LiOH·H2O 0.42 g,于室温反应10 h。过滤,滤液用10%NaH2PO4调至pH 4,用二氯甲烷(3×10 mL)萃取,合并萃取液,用饱和食盐水洗涤,无水硫酸钠干燥,旋蒸脱溶后经硅胶柱层析(洗脱剂:A=30∶1)纯化得白色固体 8 0.3 g,收率 65.2%,m.p.177.5 ℃ ~178.0 ℃,[α]20D- 16.9 °(c0.50,EtOH);1H NMR δ:1.28(s,3H,17-H),1.66(s,3H,19-H),1.69(s,3H,16-H),1.80 ~ 1.82(m,2H,2-H),1.92(m,2H,3-H),2.93~2.96(m,2H,4-H),3.43~3.46(m,1H,15-H),7.62(s,1H,9-H),7.64(s,1H,8-H),8.23(s,1H,5-H);13C NMR δ:14.85(C20),19.73(C3),23.33(C16,17),27.95(C19),28.25(C4),32.75(C15),34.68(C2),46.83(C1),122.85(C6),124.91(C9),126.10(C5),127.44(C13),130.23(C8),131.03(C10),131.25(C14),133.61(C7),139.84(C12),143.13(C1),178.50(C18);IR ν:3 436,2 961,2 868,1 698,1 464,1 401 cm-1;MSm/z:373{[M -H]+};Anal.calcd for C20H23O2Br:C 64.01,H 6.18;found C 64.15,H 6.06。
2 结果与讨论
8的1H NMR分析结果与其分子式(C20H23O2Br)一致:7.0~9.0处出现芳环上三个质子单峰,表明质子没有偶合;2.50处出现三个质子单峰,表明甲基连接在芳环上;异丙基的特征峰也很明显。在8的 IR谱中,3 436 cm-1处为羧基中OH 的伸缩振动峰,2 868 cm-1~2 961 cm-1为芳环C-H的伸缩振动吸收峰,1 698 cm-1处为羧基中 C=O的伸缩振动吸收峰,1 400 cm-1~1 464 cm-1为芳环骨架振动吸收峰。
综上分析结果表明8为预期产物6-溴-7-异丙基-1,10-二甲基-1,2,3,4-四氢蒽-1-羧酸。
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