影像科学与光化学  2015, Vol. 33 Issue (4): 265-274   PDF (870 KB)    
引用本文
黄宏丽, 高国林, 杨超, 夏吾炯, 陈晓明. 紫外光介导合成1,2,4-三芳基-1,4-丁二酮反应研究[J]. 影像科学与光化学, 2015, 33(4): 265-274.  
HUANG Hongli, GAO Guolin, YANG Chao, XIA Wujiong, CHEN Xiaoming. Synthesis of 1,2,4-Triarylbutane-1,4-Diones Using UV Light Mediated[J]. Imaging Science and Photochemistry, 2015, 33(4): 265-274.  
紫外光介导合成1,2,4-三芳基-1,4-丁二酮反应研究
黄宏丽1, 高国林1, 杨超1 , 夏吾炯1, 陈晓明2     
1. 哈尔滨工业大学 基础与交叉科学研究院, 黑龙江 哈尔滨 150080;
2. 温州医科大学 检验医学院与生命科学学院, 浙江 温州 325035
收稿日期：2015-03-31，录用日期：2015-04-22
基金项目：中央高校基本科研业务费专项基金(HIT.NSRIF.2016046)和浙江省自然科学基金(LY12B02009)资助项目
通讯作者：杨超,E-mail：xyyang@hit.edu.cn, 陈晓明,E-mail：xmchen01@163.com
摘要：在紫外光照射下,安息香发生裂解产生苯甲酰基自由基,与α,α-二芳基烯丙醇的双键发生自由基加成并伴随1,2-芳基迁移,实现了双键的双官能团化;同时该反应为有效合成1,2,4-三芳基-1,4-丁二酮化合物提供了一条新途径。该方法具有操作简单、反应条件温和等优点。
关键词： 紫外光     1,2-芳基迁移     双官能团化     1,2,4-三芳基-1,4-丁二酮    
Synthesis of 1,2,4-Triarylbutane-1,4-Diones Using UV Light Mediated
HUANG Hongli1, GAO Guolin1, YANG Chao1 , XIA Wujiong1, CHEN Xiaoming2     
1. Academy of Fundamental and Interdisciplinary Sciences, Harbin Institute of Technology, Harbin 150080, Heilongjiang, P. R. China;
2. School of Laboratory Medicine & Life Science, Wenzhou Medical University, Wenzhou 325035, Zhejiang, P. R. China
Abstract: Benzoyl radical could be generated from photochemical cleavage reaction of benzoin, which then might add to C=C double bond of α,α-diaryl allylic alcohols followed by 1,2-aryl migration to realize the difunctionalization of alkenes. The reaction provided an efficient approach to synthesize 1,2,4-triarylbutane-1,4-diones. The procedure is highlighted by its operational simplicity and mild reaction conditions.
Key words: UV light     1,2-aryl migration     difunctionalization     1,2,4-triarylbutane-1,4-dione    

烯烃的双官能团化是一类非常重要的有机化学反应，它为构建化学结构的多样性和新颖性提供了可靠的保证[1,2,3]。一般来说，实现烯烃双官能团化的反应主要是由过渡金属催化实现的[4,5,6,7]。此外，多个课题组发展了以α,α-二芳基烯丙醇为底物，通过提供自由基加成/1,2-芳基迁移的串联过程，实现双键的官能团化的新方法，同时合成了α-芳基-β-取代的羰基化合物[8,9,10,11,12,13,14,15,16]。近年来，在绿色化学理念的推动下，以光作为介质，基于C-H活化直接实现烯烃双官能团化的合成方法引起了有机化学家的广泛关注[17,18,19,20,21]。

安息香是一种稳定且易于制备的α-羟基酮，在紫外光的照射下，易发生Norrish I型裂解光化学反应产生苯甲酰基自由基。2015年，本课题组报道了以安息香为自由基源，对α-芳基烯丙醇进行苯甲酰基自由基加成/1,2-芳基迁移的串联光化学反应的研究工作[22]。在此基础上，本文设计合成了多种不对称α,α-二芳基烯丙醇，在紫外光作用下与安息香衍生物进行反应，研究电子效应对反应选择性的影响。

1 实验部分 1.1 试剂与仪器

本论文中所用试剂均为分析纯，若非特殊说 明均未进一步处理而直接使用。无水无氧反应中使用的四氢呋喃、苯、二氯甲烷、乙腈等溶剂均经过严格的除水脱氧处理。

1HNMR (400 MHz)和 13CNMR (100 MHz)： Bruker AVANCE III 400核磁共振谱仪，内标为TMS；HRMS (ESI)：Agilent 1200-6520 Q-TOF高分辨液质联用仪；GC-MS：Agilent 7890A-5975C气质联用仪；紫外光源：RPR-200光反应器，350 nm。

1.2 实验方法 1.2.1 化合物1a的合成[23]

无水无氧处理，氮气保护下，向50 mL圆底烧瓶中，加入0.55 g二苯甲酮的无水THF溶液 (20 mL)。将上述反应装置放入冰水浴，抽取2.3 mL氯乙烯基镁溶液，逐滴滴加到烧瓶中。溶液由无色变为紫色，最后变为黄色。烧瓶在冰水浴中反应30 min，后恢复至室温反应3 h。TLC监测反应完全，饱和的氯化铵溶液淬灭反应，乙酸乙酯萃取3次，合并浓缩有机相，用柱层析手段分离纯化产物，洗脱剂为石油醚/乙酸乙酯 = 18/1，得到1a (0.57 g)，产率90%。

1,1-Diphenylprop-2-en-1-ol (1a )[22]: 无色油状物。1HNMR (400 MHz,CDCl3): 7.36 (d,J=7.6 Hz,4H),7.30 (t,J=7.6 Hz,4H),7.24 (t,J=7.6 Hz,2H),6.48 (dd,J=16.8,10.8 Hz,1H),5.30 (d,J=16.8 Hz,1H),5.29 (d,J=10.8 Hz,1H),2.34 (s,1H,—OH)。 1.2.2 α,α-二芳基烯丙醇化合物的合成[15]

化合物1b~f的合成路线，如图1所示。以化合物 1b的合成为例：向50 mL圆底烧瓶中，依次加入0.6 g镁屑和半粒碘单质，冷凝，无水无氧处理，氮气保护。抽取6 mL溴苯溶液 (1.4 g溴苯，20 mL无水THF)滴加到烧瓶中，吹风机加热引发反应。引发后，将剩余的溴苯溶液逐滴滴加到烧瓶中，滴加速度使反应液保持微沸状态。待反应瓶冷却至室温，可得到溴苯格氏试剂。

图1 不对称α,α-二芳基烯丙醇化合物的合成 Synthesis of unsymmetrical α,α-diaryl allylic alcohols

无水无氧处理，氮气保护下，向50 mL圆底烧瓶中，加入0.6 g对叔丁基苯甲醛的THF (25 mL)溶液。冰浴下，抽取6 mL上述溴苯格氏试剂，逐滴滴加到反应瓶中。30 min后，去掉冰浴，室温反应3 h。TLC检测反应完全，氯化铵溶液淬灭反应，乙酸乙酯萃取。柱层析分离粗产物得到0.63 g 4-叔丁基二苯甲醇，产率71%。将得到的无色油状物溶于18 m L CH2Cl2中，经PCC氧化得到对叔丁基二苯基甲酮0.5 g，产率80%。将4-叔丁基二苯基甲酮与氯乙烯基镁发生格氏反应，得到1b (0.48 g)，产率87%。

1-(3-tert-Butylphenyl)-1-phenylprop-2-en-1-ol (1b):无色油状物。1HNMR (400 MHz,CDCl3):7.40~7.38 (m,2H),7.34~7.33(m,2H),7.32~7.29 (m,3H),7.29~7.23 (m,2H),6.50 (dd,J=16.8,10.4 Hz,1H),5.32(dd,J=16.8,1.2 Hz,1H),5.29 (dd,J=10.4,1.2 Hz,1H),2.28 (s,1H,—OH),1.30 (s,3×CH3,9H); 13CNMR (100 MHz,CDCl3): 150.1,145.7,143.6,142.7,128.1,127.1,126.8,126.6,125.1,113.6,79.2,34.4,31.3;HRMS (ESI):[M-H2O + H]+ calcd for C19H+21:249.1643,found: 249.1637。

1-(3-Methoxyphenyl)-1-phenylprop-2-en-1-ol (1c)[16]: 无色油状物。1HNMR (400 MHz,CDCl3):7.38 (d,J=7.6 Hz,2H),7.29 (t,J=7.6 Hz,2H),7.23 (d,J=7.6 Hz,1H),7.19 (d,J=7.6 Hz,1H),6.99 (d,J=1.6 Hz,1H),6.93 (dd,J=7.6,0.8 Hz,1H),6.77 (dd,J=7.6,1.6 Hz,1H),6.48 (dd,J=17.2,10.8 Hz,1H),5.29 (dd,J=17.2,1.2 Hz,1H),5.27 (dd,J=10.8,1.2 Hz,1H),3.75 (s,OCH3,3H),2.43 (s,—OH,1H)。

1-Phenyl-1-o-tolylprop-2-en-1-ol (1d)[16]: 无色油状物。1HNMR (400 MHz,CDCl3): 7.57~7.55 (m,1H),7.29 (d,J = 8.0 Hz,4H),7.25~7.19 (m,3H),7.13~7.11 (m,1H),6.52 (dd,J=17.2,10.8 Hz,1H),5.26 (d,J=10.8 Hz,1H),5.24 (d,J=17.2 Hz,1H),2.72 (s,—OH,1H),2.03 (s,CH3,3H)。

1-(2-Chlorophenyl)-1-phenylprop-2-en-1-ol (1e)[16]: 无色油状物。1HNMR (400 MHz,CDCl3):7.70 (dd,J= 7.6,2.0 Hz,1H),7.35~7.25 (m,8H),6.60 (dd,J=17.2,10.8 Hz,1H),5.34 (dd,J = 10.8,1.2 Hz,1H),5.33 (dd,J=17.2,1.2 Hz,1H),3.23 (s,—OH,1H)。

1-(2,5-Dimethoxyphenyl)-1-phenylprop-2-en-1-ol (1f): 无色油状物。1HNMR (400 MHz,CDCl3): 7.32 (dd,J=7.6,1.6 Hz,2H),7.28 (t,J=7.6 Hz,2H),7.22 (t,J= 7.6 Hz,1H),6.84 (dd,J= 8.8,1.2 Hz,2H),6.79 (dd,J= 8.8,2.8 Hz,1H),6.38 (dd,J= 17.2,10.8 Hz,1H),5.28 (dd,J= 10.8,1.2 Hz,1H),5.06 (dd,J= 17.2,1.2 Hz,1H),4.80 (s,—OH,1H),3.74 (s,OCH3,3H),3.57 (s,OCH3,3H); 13CNMR (100 MHz,CDCl3):153.5,151.3,145.7,142.5,135.3,127.7,126.8,126.5,115.7,115.0,113.4,112.3,79.5,56.3,55.6; HRMS (ESI): [M-H2O + H]+ calcd for C17H17O+2: 253.1228,found: 253.1231。

1.2.3 安息香衍生物2b~f的合成

安息香2b~f的合成与安息香2a类似[24]。在15 mL封管中，加入0.45 g 维生素B1、1 mL H2O 和3.5 mL乙醇，摇匀溶解后将烧瓶置于冰水浴中冷却。用10 %的氢氧化钠溶液调pH=9~10。加入3 mL 对甲氧基苯甲醛，密封。水浴温度75 ℃，反应6 h，冷却析出浅黄色固体。乙酸乙酯萃取，柱层析手段分离纯化产物，洗脱剂为石油醚/乙酸乙酯=6/1，得到2b (0.98 g)，产率61%。

2-Hydroxy-1,2-bis(4-methoxyphenyl)ethanone (2b): 无色固体。1HNMR (400 MHz,CDCl3): 7.89 (d,J=8.8 Hz,2H),7.24 (d,J=8.8 Hz,2H),6.85 (d,J=8.8 Hz,2H),6.84 (d,J=8.8 Hz,2H),5.85 (d,J= 5.8 Hz,1H),4.57 (d,J= 5.8 Hz,1H,—OH),3.81 (s,OCH3,3H),3.75 (s,OCH3,3H); 13CNMR (100 MHz,CDCl3): 197.3,163.9,159.6,131.8,131.5,129.0,126.3,114.5,113.9,75.2,55.4,55.2; HRMS (ESI): [M+Na]+ calcd for C16H16NaO+4: 295.0946,found: 295.0948。

1,2-Bis(4-tert-butylphenyl)-2-hydroxyethanone (2c): 无色固体。1HNMR (400 MHz,CDCl3): 7.89 (d,J=8.4 Hz,2H),7.42 (d,J=8.4 Hz,2H),7.35 (d,J=8.4 Hz,2H),7.27 (d,J= 8.4 Hz,2H),5.91 (d,J= 6.2 Hz,1H),4.51 (d,J= 6.2 Hz,1H,—OH),1.29 (s,3×CH3,9H),1.27 (s,3×CH3,9H); 13CNMR (100 MHz,CDCl3):198.4,157.8,151.5,136.3,130.9,129.2,127.4,126.1,125.7,75.7,35.2,34.6,31.2,31.0; HRMS(ESI):[M+Na]+ calcd for C22H28NaO+2: 347.1987,found: 347.2017。

1,2-Bis(4-fluorophenyl)-2-hydroxyethanone (2d): 无色固体。1HNMR (400 MHz,CDCl3): 7.94 (d,J=8.8 Hz,1H),7.93 (d,J=8.8 Hz,1H),7.31 (d,J=8.8 Hz,1H),7.30 (d,J=8.8 Hz,1H),7.09 (t,J=8.8 Hz,2H),7.03 (t,J= 8.8 Hz,2H),5.90 (d,J= 6.0 Hz,1H),4.51 (d,J= 6.0 Hz,1H,—OH); 13CNMR (100 MHz,CDCl3):197.2,166.1 (d,J=255.7 Hz),162.9(d,J= 246.7 Hz),134.8 (d,J= 3.3 Hz),131.8 (d,J= 9.5 Hz),129.7 (d,J= 3.1 Hz),129.5 (d,J= 8.3 Hz),116.2 (d,J=21.7 Hz),116.1(d,J= 22.0 Hz),75.4; HRMS (ESI): [M+Na]+ calcd for C14H10F2NaO+2: 271.0547,found: 271.0551。

2-Hydroxy-1,2-bis(3-methoxyphenyl)ethanone (2e):无色固体。1HNMR (400 MHz,CDCl3): 7.49 (d,J=8.0 Hz,1H),7.46 (s,1H),7.30 (t,J= 8.0 Hz,1H),7.25 (t,J= 8.0 Hz,1H),7.07 (dd,J= 8.0,2.4 Hz,1H),6.94 (d,J= 8.0 Hz,1H),6.87 (s,1H),6.82 (dd,J=8.0,2.4 Hz,1H),5.91 (d,J= 6.4 Hz,1H),4.53 (dd,J= 6.4,1.6 Hz,1H,—OH),3.80 (s,OCH3,3H),3.76 (s,OCH3,3H); 13CNMR (100 MHz,CDCl3): 198.7,160.1,159.7,140.4,134.7,130.1,129.6,121.7,120.4,120.1,114.1,113.3,113.1,76.2,55.4,55.2; HRMS (ESI): [M+Na]+ calcd for C16H16NaO+4: 295.0946,found: 295.0951。

2-Hydroxy-1,2-bis(2-methoxyphenyl)ethanone (2f): 无色固体。1HNMR (400 MHz,CDCl3): 7.69 (dd,J= 7.6,1.6 Hz,1H),7.37 (t,J=7.6 Hz,1H),7.21~7.15(m,2H),6.93(t,J=7.6 Hz,1H),6.84(t,J= 7.6 Hz,1H),6.77(t,J=7.6 Hz,2H),6.12 (d,J=5.6 Hz,1H),4.47(d,J=5.6 Hz,1H,—OH),3.73 (s,OCH3,3H),3.72 (s,OCH3,3H); 13CNMR (100 MHz,CDCl3): 201.6,158.1,157.2,133.8,130.6,129.9,129.5,127.5,125.3,120.5,120.5,111.2,110.8,75.8,55.2,55.1; HRMS (ESI): [M+Na]+ calcd for C16H16NaO+4: 295.0946,found: 295.0943。

1.2.4 烯丙醇衍生物1a~f的光化反应

向50 mL的光照管中，依次加入1a (0.3 mmol,63 mg)，安息香2a(1.5 mmol,318 mg)，15 mL无水苯使其溶解，搅拌下通氮气30 min后，将光照管密封。在350 nm 光源光照下，反应34 h。硅胶柱层析(石油醚/乙酸乙酯=15/1)得到无色油状物3a 61 mg，产率为65%，转化率为100%。

1,2,4-Triphenylbutane-1,4-dione (3a)[22]: 无色固体。1HNMR (400 MHz,CDCl3): 8.03 (d,J= 7.6 Hz,2H),7.97 (d,J= 7.6 Hz,2H),7.54 (t,J= 7.6 Hz,1H),7.47 (t,J= 7.6 Hz,1H),7.43 (t,J= 7.6 Hz,3H),7.37 (t,J= 7.6 Hz,3H),7.30 (t,J= 7.6 Hz,2H),7.21 (t,J= 7.6 Hz,1H),5.33 (dd,J= 10.4,3.6 Hz,1H),4.21 (dd,J= 18.0,10.4 Hz,1H),3.30 (dd,J= 18.0,3.6 Hz,1H)。

1-(4-tert-Butylphenyl)-2,4-diphenylbutane-1,4-dione (3b): 无色油状物。1HNMR (400 MHz,CDCl3):7.99 (d,J= 7.2 Hz,2H),7.97 (d,J= 7.2 Hz,2H),7.53 (t,J=7.2 Hz,1H),7.42 (t,J=7.2 Hz,4H),7.38 (d,J= 7.2 Hz,2H),7.30 (t,J= 7.2 Hz,2H),7.21 (t,J= 7.2 Hz,1H),5.32 (dd,J= 10.0,4.0 Hz,1H),4.21 (dd,J= 18.0,10.0 Hz,1H),3.29 (dd,J= 18.0,4.0 Hz,1H),1.29 (s,3×CH3,9H); 13CNMR (100 MHz,CDCl3):198.4,198.1,156.5,138.8,136.4,133.7,133.2,129.1,128.9,128.5,128.2,128.1,127.2,125.5,48.4,43.9,35.
0,31.0; HRMS (ESI): [M + Na]+calcd for C26H26O2Na+: 393.1830,found: 393.1821。

1-(3-Methoxyphenyl)-2,4-diphenylbutane-1,4-dione(3c): 无色油状物。1HNMR (400 MHz,CDCl3):8.00 (d,J=7.2 Hz,2H),7.66 (d,J=7.2 Hz,1H),7.59~7.55 (m,2H),7.46 (t,J= 8.0 Hz,2H),7.38 (d,J= 7.2 Hz,2H),7.34~7.30 (m,3H),7.24 (t,J= 7.2 Hz,1H),7.05 (dd,J=8.0,2.0 Hz,1H),5.32 (dd,J=10.0,3.6 Hz,1H),4.22(dd,J=18.0,10.0 Hz,1H),3.81 (s,OCH3,3H),3.32 (dd,J=18.0,3.6 Hz,1H); 13CNMR (100 MHz,CDCl3):198.7,198.0,159.6,138.6,137.7,136.4,133.2,129.4,129.2,128.5,128.2,128.1,127.3,121.6,119.6,
113.0,55.3,48.8,43.9; HRMS (ESI): [M+Na]+calcd for C23H20O3Na+: 367.1310,found: 367.1303。

2,4-Diphenyl-1-o-tolylbutane-1,4-dione (3d) : 无色油状物。1HNMR (400 MHz,CDCl3):8.03 (d,J=7.6 Hz,2H),7.94 (d,J=7.6 Hz,1H),7.58 (t,J=7.6 Hz,1H),7.47 (t,J= 7.6 Hz,2H),7.32~7.29 (m,5H),7.24 (t,J=7.6 Hz,2H),7.16(d,J=7.6 Hz,1H),5.16(dd,J=10.4,3.6 Hz,1H),4.28 (dd,J=18.0,10.4 Hz,1H),3.30 (dd,J=18.0,3.6 Hz,1H),2.30 (s,CH3,3H); 13CNMR (100 MHz,CDCl3): 202.6,198.2,138.3,138.2,137.7,136.5,133.2,131.4,130.9,129.0,128.6,128.5,128.4,128.1,127.4,125.4,51.7,43.2,20.6; HRMS (ESI): [M+Na]+calcd for C23H20O2Na+: 351.1361,found: 351.1339。

1-(2-Chlorophenyl)-2,4-diphenylbutane-1,4-dione(3e): 无色油状物。1HNMR (400 MHz,CDCl3): 8.02(d,J=7.6 Hz,2H),7.79 (dd,J=6.4,2.8 Hz,1H),7.58 (t,J=7.6 Hz,1H),7.47 (t,J=7.6 Hz,2H),7.35~7.28 (m,7H),7.26~7.22 (m,1H),5.18 (dd,J=9.6,4.0 Hz,1H),4.23 (dd,J=18.0,9.6 Hz,1H),3.34 (dd,J=18.0,4.0 Hz,1H); 13CNMR (100 MHz,CDCl3):200.4,197.9,138.5,136.7,136.5,133.3,131.5,131.5,130.5,129.4,129.0,128.7,128.6,128.1,127.6,126.5,
52.6,42.5; HRMS (ESI): [M+ Na]+ calcd forC22H17ClNaO+2: 371.0824,found:371.0815。

1-(3,5-Dimethoxyphenyl)-2,4-diphenylbutane-1,4-dione (3f): 无色油状物。1HNMR (400 MHz,CDCl3):8.04 (d,J=7.2 Hz,2H),8.00 (d,J=7.2 Hz,2H),7.56 (t,J= 7.2 Hz,1H),7.50~7.43 (m,3H),7.65 (t,J= 7.6 Hz,1H),7.38 (t,J= 7.2 Hz,1H),6.84 (d,J= 8.0 Hz,1H),6.75 (s,1H),6.74 (d,J= 8.0 Hz,1H),5.74 (dd,J= 10.4,3.2 Hz,1H),4.12 (dd,J= 17.6,10.4 Hz,1H),3.87 (s,OCH3,3H),3.70 (s,OCH3,3H),3.20 (dd,J=17.6,3.2 Hz,1H); 13CNMR (100 MHz,CDCl3): 199.3,198.3,153.7,150.2,136.6,136.3,133.0,132.8,128.8,128.5,128.3,128.1,128.0,114.6,112.9,112.0,56.0,
55.6,42.3,41.3; HRMS (ESI): [M + Na]+ calcd for C24H22NaO+4: 397.1416,found: 397.1396。

1.2.5 安息香衍生物2b~f的光化反应

安息香 3ab~f的合成与3a类似。4-(4-Methoxyphenyl)-1,2-diphenylbutane-1,4-dione (3ab): 无色油状物。1HNMR (400 MHz,CDCl3): 8.05 (d,J=7.6 Hz,2H),7.97 (d,J=8.8 Hz,2H),7.49 (t,J=7.6 Hz,1H),7.41 (t,J=7.6 Hz,2H),7.38 (d,J=7.6 Hz,2H),7.32 (t,J=7.6 Hz,2H),7.23 (t,J=7.6 Hz,1H),6.92 (d,J=8.8 Hz,2H),5.33 (dd,J=10.0,3.6 Hz,1H),4.18(dd,J=18.0,10.0 Hz,1H),3.86 (s,OCH3,3H),3.28 (dd,J= 18.0,3.6 Hz,1H); 13CNMR (100 MHz,CDCl3): 199.0,196.5,163.6,138.8,136.5,132.8,130.4,129.6,129.1,128.9,128.4,128.2,127.3,113.7,55.4,48.7,43.5; HRMS (ESI): [M+Na]+ calcd forC23H20NaO+3: 367.1310,found: 367.1308。

4-(4-tert-Butylphenyl)-1,2-diphenylbutane-1,4-dione (3ac): 无色油状物。1HNMR (400 MHz,CDCl3): 8.05 (d,J=8.6 Hz,2H),7.94 (d,J= 8.6 Hz,2H),7.50 (t,J= 8.0 Hz,1H),7.47 (d,J=8.0 Hz,2H),7.41 (t,J= 8.0 Hz,2H),7.38 (d,J=7.2 Hz,2H),7.32 (t,J=7.2 Hz,2H),7.24 (t,J=7.2 Hz,1H),5.35 (dd,J=10.0,4.0 Hz,1H),4.21 (dd,J=18.0,10.0 Hz,1H),3.31 (dd,J=18.0,4.0 Hz,1H),1.35 (s,3×CH3,9H); 13CNMR (100 MHz,CDCl3):199.0,197.7,157.0,138.8,136.5,133.9,132.8,129.1,128.9,128.5,128.2,128.1,127.3,125.5,48.7,
43.7,35.1,31.1; HRMS (ESI): [M+Na]+calcd for C26H26NaO+2: 393.1830,found: 393.1831。

4-(4-Fluorophenyl)-1,2-diphenylbutane-1,4-dione (3ad): 无色油状物。1HNMR (400 MHz,CDCl3): 8.03 (m,4H),7.50 (t,J=7.2 Hz,1H),7.41 (t,J=7.2 Hz,2H),7.37 (d,J=7.2 Hz,2H),7.33 (t,J=7.2 Hz,2H),7.24 (t,J=7.2 Hz,1H),7.12 (t,J=7.2 Hz,2H),5.33 (dd,J=10.0,3.8 Hz,1H),4.20 (dd,J=18.0,10.0 Hz,1H),3.27(dd,J=18.0,3.8 Hz,1H); 13CNMR(100 MHz,CDCl3):198.8,196.5,165.8 (d,J=253.3 Hz),138.5,136.4,132.9,132.9,130.8 (d,J=9.3 Hz),129.2,128.9,128.5,128.2,127.4,115.6 (d,J=21.8 Hz),48.7,43.7; HRMS (ESI): [M + Na]+ calcd for C22H17FNaO+2: 355.1110,found: 355.1117。

4-(3-methoxyphenyl)-1,2-diphenylbutane-1,4-dione (3ae): 无色油状物。1HNMR (400 MHz,CDCl3):8.05 (d,J=7.2 Hz,2H),7.60 (d,J=7.6 Hz,1H),7.50 (s,1H),7.50 (t,J=7.6 Hz,1H),7.41 (t,J=8.0 Hz,2H),7.40~7.36(m,3H),7.33 (t,J=7.6 Hz,2H),7.24 (t,J=7.2 Hz,1H),7.12 (dd,J=8.0,0.2 Hz,1H),5.33 (dd,J=10.0,4.0 Hz,1H),4.21 (dd,J=18.0,10.0 Hz,1H),3.84 (s,OCH3,3H),3.32 (dd,J=18.0,4.0 Hz,1H); 13CNMR (100 MHz,CDCl3):198.9,197.9,159.8,138.6,137.8,136.5,132.9,129.5,129.2,128.9,128.5,128.2,127.3,120.9,120.0,
112.1,55.4,48.7,44.0; HRMS (ESI):[M+Na]+ calcdfor C23H20NaO+3: 367.1310,found: 367.1321。

4-(2-Methoxyphenyl)-1,2-diphenylbutane-1,4-dione (3af): 无色油状物。1HNMR (400 MHz,CDCl3):8.04 (d,J=7.2 Hz,2H),7.75 (dd,J=7.2,1.6 Hz,1H),7.51~7.44 (m,2H),7.40 (t,J=7.2 Hz,2H),7.36 (d,J=7.2 Hz,2H),7.31 (t,J=7.2 Hz,1H),7.22 (t,J=7.2 Hz,1H),7.00~6.95 (m,2H),5.32 (dd,J=10.0,4.0 Hz,1H),4.17 (dd,J=18.8,10.0 Hz,1H),3.88 (s,OCH3,3H),3.41 (dd,J=18.8,4.0 Hz,1H); 13CNMR (100 MHz,CDCl3):199.7,199.3,159.0,139.0,136.7,133.7,132.7,130.6,129.0,128.9,128.4,128.3,127.4,127.1,120.6,
111.5,55.5,49.1,48.9; HRMS (ESI): [M+Na]+ calcdfor C23H20NaO+3: 367.1310,found: 367.1305。

2 结果与讨论 2.1 1a~f 与2a的光化反应 2.1.1 实验条件优化

以1a (0.3 mmol,63 mg)和安息香2a (1.5 mmol,318 mg)的反应为模板反应，对光化反应条件进行筛选优化。由表1可知，在测试的所有溶剂中，苯的效果最好，产率为56%。当改变苯的体积时，反应液浓度为0.02 mol/L，光照34 h后，1a被完全转化，3a的产率最高为65%。在300 nm波长照射和2当量2a的条件下，3a的产率降低到38%和32%。因此，该光化反应的最优条件是350 nm 波长照射下，无水苯为溶剂，5当量的2a为自由基源，浓度为0.02 mol/L时，3a的产率最高。

表1 光化反应的优化条件a Optimization of photochemical reaction conditions
2.1.2底物拓展

接下来的研究主要是对烯丙醇底物进行扩展：在最优光化反应条件下，1b~f分别与2a反应，其实验结果见表2。基团R的取代位置(对位、间位、邻位)不影响光化反应的发生。芳环上不管是连有吸电子基团还是供电子基团的α,α-二 芳基烯丙醇都能够被完全转化，与2a发生反应，生成中等产率的1,2,4-三芳基-1,4-丁二酮化合物。产物中，主要得到的是以苯基迁移为主的酮化合物。

表2 光化反应的底物扩展a The scope of photochemical reaction
2.2 1a与2b~f的光化反应 2.2.1安息香底物拓展

研究中还对安息香底物进行了扩展：在最优光化反应条件下，1a分别与2b~f反应，其实验结果见表3。基团R的取代位置(对位、间位、邻位)和取代成分(吸电子基团或供电子基团)均不影响光化反应的发生，都能得到1,2,4-三芳基-1,4-丁二酮化合物。从反应时间和产率上来看：对位、邻位上为带有供电子基团的芳环时，反应速率加快，产率达到90%。当对位为带有吸电子基团的芳环或间位为带有供电子基团的芳环时，反应时间增 长，得到中等产率的产物。上述结果表明，电子效应影响着芳基迁移的速率。

表3 安息香底物扩展a The scope of benzoin
2.2.2机理研究

根据我们组以前报道的工作[22]，并结合观察到的实验现象，我们推测可能的实验机理如图2所示。在紫外光的照射下，安息香 2 发生Norrish I型裂解，生成苯甲酰基自由基 4。自由基4与烯丙醇底物1发生分子间自由基加成，生成烷基自由基5。随后，5 通过分子内自由基加成产生螺[2, 5]辛二烯基自由基 6 [25,26]。自由基 6 发生1,2-芳基迁移，苯环恢复稳定结构，产生自由基 7 [27,28]。 7 失去H·后，转化成1,2,4-三芳基-1,4-丁二酮化合物 3 。

图2 可能的反应机理 Proposed mechanism
3 结论

本文以α,α-二芳基烯丙醇和安息香为底物，通过苯甲酰基自由基加成/1,2-芳基迁移实现烯烃的双官能团化，提供了一种直接合成1,2,4-三芳基-1,4-丁二酮类衍生物的新颖的光化学方法。该反应具有条件温和，环境友好，底物官能团容忍性好的优点。同时，此光化学反应进一步拓展了Norrish I型反应在有机合成中的应用。

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