
Citation: Maoxiang Zhou, Leilei Zhang, Jeffrey T. Miller, Xiaofeng Yang, Xiaoyan Liu, Aiqin Wang, Tao Zhang. Hydrogen auto-transfer under aerobic oxidative conditions: Efficient synthesis of saturated ketones by aerobic C-C cross-coupling of primary and secondary alcohols catalyzed by a Au6Pd/resin catalyst[J]. Chinese Journal of Catalysis, 2016, 37(10): 1764-1770. doi: 10.1016/S1872-2067(16)62511-1

Au6Pd/resin催化伯醇和仲醇氧化偶联-转移加氢反应制备酮类化合物
AuPd/resin催化剂采用离子交换-NaBH4还原法制备.TEM照片显示Au,Pd以及双金属AuPd纳米颗粒均匀分散在载体上,平均粒径为2-4 nm,而且随着Au/Pd比例减小,AuPd纳米颗粒的粒径逐渐减小.XRD谱图显示,随着Au/Pd比例减小,Au(111)衍射峰逐渐向高角度发生偏移,说明AuPd形成了合金.
我们以苯甲醇和(±)-1-苯乙醇氧化偶联为探针反应考察了催化剂的催化性能.结果显示,以Au/resin和Pd/resin为催化剂时,产物为不饱和酮.而以AuPd/resin为催化剂时,转化率显著提高,说明AuPd之间存在明显的协同作用.而且随着Au/Pd比例增加,产物逐渐由不饱和酮转变为饱和酮,当Au/Pd≥6时,产物完全为饱和酮,说明反应过程中发生了“氢转移”.为验证这一推测,我们以苯甲醇和查尔酮为底物在相同条件下反应.结果显示,以Au/resin和Pd/resin为催化剂时,查尔酮没有转化.而以AuPd/resin为催化剂时,查尔酮大部分转化为饱和酮(转化率为91%),验证了反应中发生了“氢转移”的推测.
为研究“氢转移”发生的机理,我们采用XAFS对催化剂价态进行了表征.Pd元素K边X射线吸收谱图显示,随着催化剂中Au/Pd比例的增加,E0值逐渐减小,说明Pd价态逐渐降低.EXAFS拟合数据表明,随催化剂中Au/Pd比例增加,Pd-O配位数逐渐减小.基于以上结果推断,在AuPd/resin催化剂中,随着Au/Pd比例的增加,Pd的抗氧化能力显著增强,更多的Pd以Pd(0)形式存在.结合文献报道结果,我们认为正是催化剂中的Pd(0)夺取了醇的βC-H后生成了Pd-H,而Pd-H是“氢转移”反应的催化剂.
另一方面,有文献报道,在氧化气氛下,O2也可以辅助脱除醇的βC-H.为区分Pd(0)和O2在脱除醇βC-H中的作用,我们对Au6Pd/resin在惰性气氛下对伯醇(苯甲醇)或仲醇((±)-1-苯乙醇)转化的催化性能进行了考察.结果显示,苯甲醇可以转化为苯甲酸(收率为23%),而(±)-1-苯乙醇则完全没有转化.这说明伯醇可以直接被催化剂(Pd(0))活化,而仲醇的活化则必须有O2参与.综上,我们提出伯醇和仲醇氧化偶联反应的机理:Au6Pd/resin催化伯醇转化为醛(同时产生Pd-H物种),而O2辅助活化仲醇转化为酮.醛和酮发生aldol缩合生成α,β不饱和酮,该中间物种被Pd-H加氢生成饱和产物.
English
Hydrogen auto-transfer under aerobic oxidative conditions: Efficient synthesis of saturated ketones by aerobic C-C cross-coupling of primary and secondary alcohols catalyzed by a Au6Pd/resin catalyst
-
-
[1] C. Liu, H. Zhang, W. Shi, A. W. Lei, Chem. Rev., 2011, 111, 1780-1824.
-
[2] F. Y. Mo, G. B. Dong, Science, 2014, 345, 68-72.
-
[3] J. C. Tellis, D. N. Primer, G. A. Molander, Science, 2014, 345, 433-436.
-
[4] N. Kambe, T. Iwasaki, J. Terao, Chem. Soc. Rev., 2011, 40, 4937-4947.
-
[5] L. L. Zhang, A. Q. Wang, J. T. Miller, X. Y. Liu, X. F. Yang, W. T. Wang, L. Li, Y. Q. Huang, C. Y. Mou, T. Zhang, ACS Catal., 2014, 4, 1546-1553.
-
[6] Z. W. Zuo, D. T. Ahneman, L. L. Chu, J. A. Terrett, A. G. Doyle, D. W. C. MacMillan, Science, 2014, 345, 437-440.
-
[7] C. Gunanathan, D. Milstein, Science, 2013, 341, 249.
-
[8] C. S. Cho, B. T. Kim, H. S. Kim, T. J. Kim, S. C. Shim, Organometallics, 2003, 22, 3608-3610.
-
[9] K. I. Fujita, C. Asai, T. Yamaguchi, F. Hanasaka, R. Yamaguchi, Org. Lett., 2005, 7, 4017-4019.
-
[10] C. S. Cho, W. X. Ren, S. C. Shim, Bull. Korean Chem. Soc., 2005, 26, 1611-1613.
-
[11] K. I. Shimizu, R. Sato, A. Satsuma, Angew. Chem. Int. Ed., 2009, 48, 3982-3986.
-
[12] X. Liu, R. S. Ding, L. He, Y. M. Liu, Y. Cao, H. Y. He, K. N. Fan, ChemSusChem, 2013, 6, 604-608.
-
[13] T. Ishida, M. Haruta, Angew. Chem. Int. Ed., 2007, 46, 7154-7156.
-
[14] X. Liu, L. He, Y. M. Liu, Y. Cao, Acc. Chem. Res., 2014, 47, 793-804.
-
[15] T. Mitsudome, K. Kaneda, Green Chem., 2013, 15, 2636-2654.
-
[16] Y. Zhang, X. J. Cui, F. Shi, Y. Q. Deng, Chem. Rev., 2012, 112, 2467-2505.
-
[17] W. J. Li, A. Q. Wang, X. Y. Liu, T. Zhang, Appl. Catal. A., 2012, 433-434, 146-151.
-
[18] W. J. Li, A. Q. Wang, X. F. Yang, Y. Q. Huang, T. Zhang, Chem. Com-mun., 2012, 48, 9183-9185.
-
[19] L. L. Zhang, W. T. Wang, A. Q. Wang, Y. T. Cui, X. F. Yang, Y. Q. Huang, X. Y. Liu, W. G. Liu, J. Y. Son, H. Oji, T. Zhang, Green Chem., 2013, 15, 2680-2684.
-
[20] X. Y. Liu, A. Q. Wang, L. Li, T. Zhang, C. Y. Mou, J. F. Lee, J. Catal., 2011, 278, 288-296.
-
[21] X. Y. Liu, A. Q. Wang, X. Wang, C. Y. Mou, T. Zhang, Chem. Commun., 2008, 3187-3189.
-
[22] X. Liu, A. Wang, X. P. Yang, T. Zhang, C. Y. Mou, D. S. Su, J. Li, Chem. Mater., 2009, 21, 410-418.
-
[23] L. L. Zhang, A. Q. Wang, W. T. Wang, Y. Q. Huang, X. Y. Liu, S. Miao, J. Y. Liu, T. Zhang, ACS Catal., 2015, 5, 6563-6572.
-
[24] G. X. Pei, X. Y. Liu, A. Q. Wang, A. F. Lee, M. A. Isaacs, L. Li, X. L. Pan, X. F. Yang, X. D. Wang, Z. J. Tai, K. Wilson, T. Zhang, ACS Catal., 2015, 5, 3717-3725.
-
[25] T. Mallat, A. Baiker, Chem. Rev., 2004, 104, 3037-3058.
-
-

计量
- PDF下载量: 5
- 文章访问数: 730
- HTML全文浏览量: 93