图图式1 传统与本研究合成羟嗪的方法
图式1. Traditional and our methods to get hydroxyzine
近年来在过渡金属催化下直接利用醇与胺进行氮烷基化的方法取得了长足的发展[4].此类方法与传统方法相比其优势在于生成的副产物仅为水, 可避免使用卤代物带来的环境问题, 且相应的醇往往比卤代物更易得, 因此成本也更加低廉.
羟嗪(Dihydrochloride, 1a, 图 1)是一种组胺受体拮抗剂, 对胆碱、肾上腺素与血清素激活受体存在抑制作用, 可用于精神疾病的治疗或镇静, 对由焦虑、紧张、激动而引起的情绪或精神障碍有较好的疗效[1, 2].羟嗪既可作药品, 另一方面也是合成二代抗组胺药西替利嗪(Cetirizine)的原料.因此此药物的合成一直广受关注, 其关键步骤为仲胺的烷基化反应, 传统方法是利用卤代物与仲胺在碱性条件下发生SN2反应实现(Scheme 1)[3], 在此过程中不可避免地使用了毒性较高的卤化物, 这些卤化物在制备和使用过程中均会带来一系列环境问题.
目前如Pd[5~7], Ru[8, 9], Ir[10, 11], Cu[12], Fe[13], Ni[14~16]等多种金属被利用在催化此类反应上, 极大地扩展了此方法在合成上的应用, 但不足的是这些金属成本较高[8~11], 条件要求苛刻[6], 催化剂难以制备[14], 或需要强碱不适用于工业生产[12, 13].Garcia等[15]在2009年偶然发现利用Raney Ni为催化剂乙醇为溶剂的条件下可以成功将伯胺乙基化, 但Garcia等的方法仅能够应用于伯胺与低级脂肪醇, 且必须用相应的醇作溶剂, 某种程度上限制了此方法的应用, Mehta等[16]在2014年对此方法进行了拓展, 但其底物多为苯胺与苄醇类化合物, 因此如何使用Raney Ni催化其它类型的氨与更复杂的醇进行烷基化反应, 发展出更加绿色高效的合成方法成为目前药物合成研究的热点.因此本研究使用Raney Ni催化氮烷基化方法合成抗组胺药物羟嗪, 同时对其反应条件进行优化, 拓展其底物范围, 提高此类方法在药物合成方面的应用价值.
本研究以4-氯二苯甲酮为原料, 利用文献报道的方法[17], 优化条件, 通过四步反应以80%的总收率成功得到关键中间体化合物2a (Scheme 2).
采用1, 4-二氧六环作为溶剂的收率高于二甲苯, 可能原因是1, 4-二氧六环的良好水溶性分散了反应产生的水, 进而对反应有促进作用, 而在此反应条件下将反应时间延长至8 h, 对收率的影响不大.因此我们以1, 4-二氧六环为溶剂, 反应时间4 h, 考察了缩乙二醇用量对反应的影响(表 2).
在最初的研究中, 按照文献条件[15]在室温下进行氮烷基化反应, 但并没有得到产物.可能的原因为仲胺与缩乙二醇位阻均较大, 室温难以提供反应所需的活化能.为了验证此推测, 将反应体系升温至110℃反应3 h, TLC监测原料点消失.但是由于使用大量高沸点的缩乙二醇(沸点: 245 ℃)同时作为反应物与溶剂参与反应, 产物难以分离纯化.为解决此问题减少缩乙二醇用量, 研究反应溶剂的影响, 我们引入溶剂对反应体系进行分散, 首先尝试了文献报道过的二甲苯作为溶剂[16], 但收率仅有43%~45%, 于是采用沸点相近且与水有良好互溶性的1, 4-二氧六环对反应体系进行分散, 反应结果如下表 1所示.
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| Entry | Solvent | Time/h | Temperature/℃ | Yieldb/% |
| 1 | Diethylene glycol | 15 | 20 | - |
| 2 | Xylene | 4 | 110 | 43 |
| 3 | Xylene | 6 | 110 | 45 |
| 4 | 1, 4-Dioxane | 4 | 110 | 78 |
| 5 | 1, 4-Dioxane | 8 | 110 | 80 |
| aReaction conditions: compound 2a 2 mmol, compound 4a 20 mmol, Raney Ni 1.2 g, solvent 10 mL, under N2; bisolated yields. | ||||
| Entry | Time/h | Amount of 2a/4a(mmol) | Yieldb/% |
| 1 | 4 | 2/2 | 31 |
| 2 | 4 | 2/3 | 53 |
| 3 | 4 | 2/6 | 68 |
| 4 | 4 | 2/8 | 78 |
| 5 | 6 | 2/10 | 75 |
| 6 | 6 | 2/20 | 80 |
| aReaction conditions: Raney Ni 1.2 g, 1, 4-dioxane 10 mL, 110 ℃, under N2; bisolated yields. | |||
由表 2可发现, 当缩乙二醇用量为底物1~3 equiv.时收率仅有31%~68% (Entries 1~3), 而其用量为底物4 equiv.倍收率达到稳定(78%), 再提高缩乙二醇用量对收率影响不大(Entries 5, 6), 因此以4 equiv.的缩乙二醇为最优条件对底物进行拓展.
在最佳反应条件下, 利用不同醇和哌嗪类化合物反应, 进一步考察了反应对底物的普适性, 结果如表 3所示.结果显示长链醇与仲胺在此反应条件下均能取得60%以上收率(Entries 2~8), 随着链长的增加产率略有下降.二醇类化合物能顺利反应且未发生二取代(Entries 1, 9, 10), 其中包括另一种抗组胺药物去氯羟嗪(Decloxizine, Entry 10, 1k).苄醇类底物较之脂肪醇底物收率略高, 在79%~86%之间(Entries 11~14), 我们首次利用此方法高收率地得到抗组胺药物美克洛嗪(Meclizine, Entry 12, 1l)、布克利嗪(buclizine, Entry 13, 1m)与钙离子通道阻滞剂洛美利嗪(Lomerizine, Entry 14, 1n).
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| Entry | Product | R1 | R2 | R3 | Yieldb/% |
| 1 | 1a | Cl | H | ![]() |
78 |
| 2 | 1b | Cl | H | ![]() |
81 |
| 3 | 1c | Cl | H | ![]() |
78 |
| 4 | 1d | Cl | H | ![]() |
73 |
| 5 | 1e | Cl | H | ![]() |
71 |
| 6 | 1f | Cl | H | ![]() |
66 |
| 7 | 1g | Cl | H | ![]() |
79 |
| 8 | 1h | Cl | H | ![]() |
80 |
| 9 | 1i | Cl | H | ![]() |
73 |
| 10 | 1j | H | H | ![]() |
80 |
| 11 | 1k | Cl | H | ![]() |
86 |
| 12 | 1l | Cl | H | ![]() |
84 |
| 13 | 1m | Cl | H | ![]() |
83 |
| 14 | 1n | F | F | ![]() |
79 |
| aReaction conditions: Raney Ni 1.2 g, compound 2 2 mmol, compound 4 8 mmol, 1, 4-dioxane 10 mL, 110℃, under N2, 4 h; bisolated yields. | |||||
根据以往有关Ni催化氮烷基化的机理报道[14, 17]与实验结果, 我们推测了反应的机理为“借氢”(Borrowing Hydrogen)机理(Scheme 3).首先, Raney-Ni从相应的醇中“借氢”, 形成[MH2], 而醇转化为相应的醛.随后, 醛在[MH2]存在下与仲胺发生还原胺化反应, 生成目标产物.
本研究首次利用相对环保的新型氮烷基化方法合成了抗组胺药物羟嗪(Dihydrochloride, 1a), 优化了反应条件, 发展了一种催化剂易得, 简单高效, 普适性好的合成此类化合物的新方法, 且成功地利用此方法高收率合成了抗组胺药物去氯羟嗪(Decloxizine, 1j)、美克洛嗪(Meclizine, 1l)、布克利嗪(Buclizine, 1m)与钙离子通道阻滞剂洛美利嗪(Lomerizine, 1n).极大地拓展了此方法在药物合成方面的应用, 探索出一条更加简便, 相对绿色地合成此类药物的通用方法.
1H NMR (400 MHz)和13C NMR (100 MHz)采用Bruker AV 400核磁共振仪测定, 所用溶剂为CDCl3, TMS为内标物; HRMS (ESI)采用Thermo Scientific LTQ Orbitrap Discovery高分辨质谱仪; 熔点用X-5显微熔点仪测定.本实验所用柱层析硅胶为青岛海洋化工有限公司生产(100~200目); 实验所用试剂均为市售分析化试剂.
将4-氯二苯氯甲烷(7, 5.4 g, 22.8 mmol), 无水哌嗪(3.1 g, 36.1 mmol), 碳酸钾(6.3 g, 45.6 mmol), 苄基三乙基溴化铵(BTEAB) (0.3 g)和KI (0.3 g)溶于乙腈60 mL中, 升温至80 ℃反应8 h, TLC监测反应完全.冷却至室温, 过滤, 用乙酸乙酯(5 mL×2)洗涤滤饼, 减压浓缩滤液, 加入50 mL水, 用2 mol/L盐酸调pH至2, 用乙酸乙酯(30 mL×3)萃取.水层用10% NaOH溶液调到pH为10, 再用乙酸乙酯(50 mL×3)萃取, 合并有机相, 无水硫酸钠干燥, 减压浓缩, 用V(乙酸乙酯):V(石油醚)=1:1进行重结晶, 得淡黄色固体1-(4-氯二苯甲基)哌嗪(2a) 5.75 g, 产率为88%.m.p.62~70 ℃; 1H NMR (CDCl3) δ: 7.36~7.09 (m, 9H), 4.12 (s, 1H), 2.81 (t, J=6 Hz, 4H), 2.35~2.27 (m, 4H); 13C NMR (100 MHz, CDCl3) δ: 142.09, 141.31, 132.52, 129.26, 128.65, 128.59, 127.91, 127.14, 75.98, 53.23, 46.23.以上数据与文献[18]报道一致.
将4-氯二苯甲醇(6, 6.0 g, 27.4 mmol)溶于25 mL浓盐酸中, 加入无水CaCl2(3.65 g, 32.9 mmol), 升温至90 oC反应3 h, TLC监测反应完全.加入25 mL水, 再用二氯甲烷(30 mL×3)萃取三次, 合并有机相, 有机相依次用饱和NaCl溶液洗涤, 无水Na2SO4干燥, 减压浓缩得无色油状物4-氯二苯氯甲烷(7) 6.2 g, 产率为96%.1H NMR (CDCl3) δ: 7.54~7.40 (m, 9H), 6.21 (s, 1H).1H NMR数据与文献[18]报道一致.
将4-氯二苯甲酮(5.0 g, 23.1 mmol)溶于甲醇, 置于冰浴中搅拌, 分批加入硼氢化钠(1.05 g, 27.7 mmol)后, 移至常温反应1 h, TLC监测反应完全.加碎冰淬灭反应, 减压蒸除大部分甲醇, 加水, 用乙酸乙酯萃取, 合并有机相, 用饱和NaCl溶液洗涤、无水Na2SO4干燥, 过滤, 减压蒸除溶剂, 得白色固体4-氯二苯甲醇(6) 4.80 g, 产率为95%.m.p.58~60 ℃; 1H NMR (400 MHz, CDCl3) δ: 7.34~7.29 (m, 9H), 6.79 (s, 1H), 2.29 (br, 1H).以上数据与文献[18]报道一致.
1-二(4-氟苯基)甲基-4-(2, 3, 4-三甲氧基苯甲基)哌嗪(1n)[20]:得黄色油状物741 mg, 收率79%.1H NMR (CDCl3) δ: 7.34~7.26 (m, 4H), 6.97~6.92 (m, 5H), 6.61 (d, J=8 Hz, 1H), 4.18 (s, 1H), 3.87 (s, 3H), 3.86 (s, 3H), 3.84 (s, 3H), 3.49 (s, 2H), 2.49~2.37 (m, 8H); 13C NMR (CDCl3) δ: 161.75 (d, J=245 Hz), 152.88, 152.62, 142.20, 138.36, 138.33, 129.24 (d, J=8 Hz), 125.26, 115.32 (d, J=21 Hz), 106.89, 74.52, 61.19, 60.78, 56.31, 55.95, 53.04, 51.80; HRMS calcd for C27H31F2N2O3 [M+H]+: 469.2303, found 469.2303.
1-[(4-氯苯基)苯基甲基]-4-丙基哌嗪(1b):得淡黄色油状物533 mg, 产率81%.1H NMR (CDCl3) δ: 7.35~7.27 (m, 4H), 7.21~7.08 (m, 5H), 4.12 (s, 1H), 2.37 (br, 8H), 2.21 (t, J=8 Hz, 2H), 1.46~1.35 (m, 2H), 0.81 (t, J=8 Hz, 3H); 13C NMR (CDCl3) δ: 142.28, 141.48, 132.49, 129.22, 128.64, 128.59, 127.87, 127.13, 75.57, 60.73, 53.46, 51.87, 20.06, 12.03; HRMS calcd for C20H26ClN2 [M+H]+: 329.1785, found 329.1786.
1-[(4-氯苯基)苯甲基]-4-[(4-羟基)丁基]哌嗪(1i):得黄色油状物524 mg, 收率73%.1H NMR (CDCl3) δ: 7.71~7.33 (m, 4H), 7.28~7.16 (m, 5H), 4.19 (s, 1H), 3.54~3.52 (m, 2H), 2.47~2.39 (m, 10H), 1.69~1.65 (m, 4H); 13C NMR (CDCl3) δ: 142.16, 141.33, 132.58, 129.10, 128.71, 128.64, 127.73, 127.20, 75.46, 62.64, 58.36, 53.10, 51.40, 32.67, 25.42; HRMS calcd for C21H28ClN2O [M+H]+: 359.1890, found 359.1890.
1-[(4-氯苯基)苯基甲基]-4-丁基哌嗪(1c):得淡黄色油状物535 mg, 收率78%.1H NMR (CDCl3) δ: 7.42~7.34 (m, 4H), 7.28~7.16 (m, 5H), 4.20 (s, 1H), 2.45 (br, 8H), 2.35 (m, 2H), 1.50~1.43 (m, 2H), 1.35~1.28 (m, 2H), 0.90 (t, J=8 Hz, 3H); 13C NMR (CDCl3) δ: 142.24, 141.44, 132.51, 129.20, 128.66, 128.61, 127.85, 127.15, 75.50, 58.45, 53.42, 51.72, 28.89, 20.83, 14.09; HRMS calcd for C21H28ClN2 [M+H]+: 343.1941, found 343.1941.
1-二苯甲基-4-(2-(2-羟基乙氧基)乙基)哌嗪(1j)[19]:得无色油状物546 mg, 收率80%.1H NMR (CDCl3) δ: 7.33 (d, J=8 Hz, 4H), 7.18 (t, J=8 Hz, 4H), 7.08 (t, J=8 Hz, 2H), 4.14 (s, 1H), 3.60~3.53 (m, 4H), 3.52~3.50 (m, 2H), 2.50 (t, J=4 Hz, 2H), 2.37 (br, 8H); 13C NMR (CDCl3) δ: 142.82, 128.51, 127.88, 126.94, 76.28, 72.49, 67.48, 62.04, 57.99, 53.58, 51.66; HRMS calcd for C21H29N2O2 [M+H]+: 341.2229, found 341.2230.
1-[(4-氯苯基)苯甲基]-4-[(3-甲苯基)甲基]-哌嗪(1l)[19]:得黄色油状物657 mg, 收率84%.1H NMR (CDCl3) δ: 7.33~7.26 (m, 4H), 7.20~7.08 (m, 7H), 7.04~6.97 (m, 3H), 4.14 (s, 1H), 3.42 (s, 2H), 2.41 (br, 8H), 2.25 (s, 3H); 13C NMR (CDCl3) δ: 142.21, 141.42, 137.82, 137.59, 132.51, 130.09, 129.24, 128.63, 128.57, 128.09, 127.89, 127.27, 127.14, 126.47, 75.45, 63.04, 53.30, 51.72, 21.41; HRMS calcd for C25H28ClN2 [M+ H]+: 391.1941, found 391.1941.
1-(4-叔丁苄基)-4-(4-氯代二苯甲基)哌嗪(1m)[19]:得淡黄色油状物720 mg, 收率83%.1H NMR (CDCl3) δ: 7.33~7.08 (m, 14H), 4.14 (s, 1H), 3.44 (s, 2H), 2.42~2.35 (m, 8H), 1.23 (s, 9H); 13C NMR (CDCl3) δ: 150.01, 142.19, 141.40, 132.49, 129.24, 129.07, 128.62, 128.56, 127.90, 127.12, 125.51, 125.10, 75.45, 62.62, 53.24, 51.74, 34.47, 31.40; HRMS calcd for C28H34ClN2 [M+H]+: 433.2411, found 433.2411.
1-[(4-氯苯基)苯基甲基]-4-[(2-甲基)丙基]哌嗪(1d):得无色油状物501 mg, 收率73%.1H NMR (CDCl3) δ: 7.35~7.27 (m, 4H), 7.21~7.08 (m, 5H), 4.12 (s, 1H), 2.34 (br, 8H), 2.02 (d, J=4 Hz, 2H), 1.72~1.56 (m, 1H), 0.81 (d, J=4 Hz, 6H); 13C NMR (CDCl3) δ: 142.38, 141.57, 132.45, 129.24, 128.62, 128.55, 127.89, 127.08, 75.61, 66.93, 53.77, 51.94, 25.36, 21.00; HRMS calcd for C21H28ClN2 [M+H]+: 343.1941, found 343.1943.
辅助材料(Supporting Information) 化合物6, 7的1H NMR, 化合物2a, 1a~1n的1H NMR和13C NMR.这些材料可以免费从本刊网站(http://sioc-journal.cn/)上下载.
1-[(4-氯苯基)苯甲基]-4-苄基哌嗪(1k):得无色油状物649 mg, 收率86%.1H NMR (CDCl3) δ: 7.33~7.08 (m, 14H), 4.14 (s, 1H), 3.46 (s, 2H), 2.42~2.36 (m, 8H); 13C NMR (CDCl3) δ: 142.23, 141.43, 137.93, 132.50, 129.30, 129.24, 128.63, 128.57, 128.20, 127.89, 127.13, 127.06, 75.47, 63.05, 53.28, 51.80; HRMS calcd for C24H26ClN2 [M+H]+: 377.1785, found 377.1785.
1-[(4-氯苯基)苯基甲基]-4-戊基哌嗪(1e):得无色油状物507 mg, 收率71%.1H NMR (CDCl3) δ: 7.43~7.34 (m, 4H), 7.28~7.14 (m, 5H), 4.19 (s, 1H), 2.44 (br, 8H), 2.31 (t, J=8 Hz, 2H), 1.48~1.43 (m, 2H), 1.34~1.23 (m, 4H), 0.88 (t, J=8 Hz, 3H); 13C NMR (CDCl3) δ: 142.28, 141.48, 132.49, 129.22, 128.65, 128.59, 127.87, 127.13, 75.56, 58.84, 53.51, 51.88, 29.88, 26.62, 22.66, 14.10; HRMS calcd for C22H30ClN2 [M+H]+: 357.2098, found 357.2098.
称量Raney Ni (1.2 g, 湿重)于50 mL单颈瓶中, 用1, 4-二氧六环(10 mL×3)洗涤, 弃去上清液, 加入30 mL 1, 4-二氧六环, 化合物2(2 mmol), 相应的醇类化合物4(8 mmol), N2保护下升温至110 ℃回流反应.回流4 h后冷却至室温, 在N2保护下减压过滤, 反应瓶壁及滤饼用1, 4-二氧六环(30 mL×3)洗涤, 滤液减压除去溶剂, 所得油状液体, 经柱层析得到目标化合物1a~1n.
1-[(4-氯苯基)苯基甲基]-4-[(2-甲氧基)乙基]哌嗪(1g):得无色油状物545 mg, 收率79%.1H NMR (CDCl3) δ:7.35~7.27 (m, 4H), 7.21~7.09 (m, 5H), 4.13 (s, 1H), 3.42 (t, J=4 Hz, 2H), 3.25 (s, 3H), 2.51 (t, J=4 Hz, 2H), 2.45~2.36 (m, 8H); 13C NMR (CDCl3) δ: 142.19, 141.40, 132.50, 129.22, 128.63, 128.58, 127.87, 127.14, 75.44, 70.08, 58.89, 57.87, 53.81, 51.61; HRMS calcd for C20H26ClN2O[M+H]+: 345.1734, found 345.1734.
1-[(4-氯苯基)苯基甲基]-4-[(2-乙氧基)乙基]哌嗪(1h):得黄色油状物575 mg, 收率80%.1H NMR (CDCl3) δ: 7.35~7.27 (m, 4H), 7.21~7.07 (m, 5H), 4.13 (s, 1H), 3.50~3.46 (m, 2H), 3.40 (q, J=6 Hz, 2H), 2.54~2.36 (m, 10H), 1.10 (t, J=6 Hz, 3H); 13C NMR (CDCl3) δ: 142.21, 141.42, 132.51, 129.21, 128.64, 128.58, 127.86, 127.14, 75.48, 68.13, 66.44, 57.86, 53.88, 51.70, 15.15; HRMS calcd for C21H28ClN2O[M+H]+: 359.1890, found 359.1889.
2-{2-[4-(4-氯苯基)苯甲基-1-哌嗪基]乙氧基}-乙醇(1a)[19]:得淡黄色油状物585 mg, 产率78%.1H NMR (CDCl3) δ: 7.42~7.34 (m, 4H), 7.28~7.14 (m, 5H), 4.20 (s, 1H), 3.68~3.64 (m, 4H), 3.63~3.59 (m, 2H), 2.59~2.44 (m, 10H); 13C NMR (CDCl3) δ: 142.25, 141.43, 132.56, 129.13, 128.71, 128.64, 127.77, 127.19, 75.50, 72.48, 67.42, 62.03, 57.94, 53.50, 51.53; HRMS calcd for C21H28ClN2O2 [M+H]+: 375.1839, found 375.1839.
1-[(4-氯苯基)苯基甲基]-4-己基哌嗪(1f):得无色油状物490 mg, 收率66%.1H NMR (CDCl3) δ: 7.42~7.34 (m, 4H), 7.28~7.14 (m, 5H), 4.19 (s, 1H), 2.44 (br, 8H), 2.31 (t, J=8 Hz, 2H), 1.47~1.44 (m, 2H), 1.27 (s, 6H), 0.88 (t, J=8 Hz, 3H); 13C NMR (CDCl3) δ: 142.27, 141.47, 132.50, 129.22, 128.64, 128.58, 127.87, 127.12, 75.55, 58.86, 53.50, 51.86, 31.81, 27.36, 26.86, 22.62, 14.08; HRMS calcd for C23H32ClN2[M+H]+: 371.2254, found 371.2254.
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表 1 反应条件优化a
Table 1. Optimization of the reaction conditions
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| Entry | Solvent | Time/h | Temperature/℃ | Yieldb/% |
| 1 | Diethylene glycol | 15 | 20 | - |
| 2 | Xylene | 4 | 110 | 43 |
| 3 | Xylene | 6 | 110 | 45 |
| 4 | 1, 4-Dioxane | 4 | 110 | 78 |
| 5 | 1, 4-Dioxane | 8 | 110 | 80 |
| aReaction conditions: compound 2a 2 mmol, compound 4a 20 mmol, Raney Ni 1.2 g, solvent 10 mL, under N2; bisolated yields. | ||||
表 2 反应物比例的影响a
Table 2. The influence of the ratio of reactants
| Entry | Time/h | Amount of 2a/4a(mmol) | Yieldb/% |
| 1 | 4 | 2/2 | 31 |
| 2 | 4 | 2/3 | 53 |
| 3 | 4 | 2/6 | 68 |
| 4 | 4 | 2/8 | 78 |
| 5 | 6 | 2/10 | 75 |
| 6 | 6 | 2/20 | 80 |
| aReaction conditions: Raney Ni 1.2 g, 1, 4-dioxane 10 mL, 110 ℃, under N2; bisolated yields. | |||
表 3 底物的拓展a
Table 3. Substrate scope
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| Entry | Product | R1 | R2 | R3 | Yieldb/% |
| 1 | 1a | Cl | H | ![]() |
78 |
| 2 | 1b | Cl | H | ![]() |
81 |
| 3 | 1c | Cl | H | ![]() |
78 |
| 4 | 1d | Cl | H | ![]() |
73 |
| 5 | 1e | Cl | H | ![]() |
71 |
| 6 | 1f | Cl | H | ![]() |
66 |
| 7 | 1g | Cl | H | ![]() |
79 |
| 8 | 1h | Cl | H | ![]() |
80 |
| 9 | 1i | Cl | H | ![]() |
73 |
| 10 | 1j | H | H | ![]() |
80 |
| 11 | 1k | Cl | H | ![]() |
86 |
| 12 | 1l | Cl | H | ![]() |
84 |
| 13 | 1m | Cl | H | ![]() |
83 |
| 14 | 1n | F | F | ![]() |
79 |
| aReaction conditions: Raney Ni 1.2 g, compound 2 2 mmol, compound 4 8 mmol, 1, 4-dioxane 10 mL, 110℃, under N2, 4 h; bisolated yields. | |||||
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