Solvent-free iodination of organic molecules using the I<sub>2</sub>/urea–H<sub>2</sub>O<sub>2</sub>reagent system
作者:Jasminka Pavlinac、Marko Zupan、Stojan Stavber
DOI:10.1039/b614819k
日期:——
Introduction of iodine under solvent-free conditions into several aromatic compounds activated toward electrophilic functionalisation was found to proceed efficiently using elemental iodine in the presence of a solid oxidiser, the ureaâH2O2 (UHP) adduct. Two types of iodo-functionalisation through an electrophilic process were observed: iodination of an aromatic ring, and side-chain iodo-functionalisation in the case of arylalkyl ketones. Two reaction routes were established based on the required substrate : iodine : oxidiser ratio for the most efficient iodo-transformation, and the role of UHP was elucidated in each route. The first, requiring a 1 : 0.5 : 0.6 stoichiometric ratio of substrate to iodine to UHP, followed the atom economy concept in regard to iodine and was valid in the case of aniline (1a), 4-t-Bu-phenol (3), 1,2-dimethoxy benzene (5a), 1,3-dimethoxy benzene (5b), 1,2,3-trimethoxy benzene (7a), 1,2,4-trimethoxy benzene (7b), 1,3,5-trimethoxy benzene (7c), 1-indanone (11a) and 1-tetralone (11b). The second reaction route, where a 1 : 1 : 1 stoichiometric ratio of substrate : I2 : UHP was needed for efficient iodination, was suitable for side-chain iodo-functionalisations of acetophenone (1c) and methoxy-substituted acetophenones. Moreover, addition of iodine to 1-octene (13a) and some phenylacetylenic derivatives (15a, 15b) was found to proceed efficiently without the presence of any oxidiser and solvent at room temperature.
在无溶剂条件下,使用固态氧化剂尿素-过氧化氢(UHP)络合物,元素碘能够高效地将碘引入多个活化芳香化合物中,这些化合物可进行亲电功能化。观察到两种通过亲电过程的碘功能化类型:芳香环的碘化反应,以及在芳基烷基酮情况下的侧链碘功能化。根据所需的底物与碘与氧化剂的比例,建立了两条反应路线,并在每条路线中阐明了UHP的作用。第一条路线需要底物与碘与UHP的摩尔比为1 : 0.5 : 0.6,遵循碘原子经济概念,适用于苯胺(1a)、4-叔丁基苯酚(3)、1,2-二甲氧基苯(5a)、1,3-二甲氧基苯(5b)、1,2,3-三甲氧基苯(7a)、1,2,4-三甲氧基苯(7b)、1,3,5-三甲氧基苯(7c)、1-茚酮(11a)和1-四氢萘酮(11b)。第二条反应路线需要底物、碘和UHP的摩尔比为1 : 1 : 1才能有效进行碘化反应,适用于苯乙酮(1c)和甲氧基取代的苯乙酮的侧链碘功能化。此外,在室温下,碘与1-辛烯(13a)以及一些苯乙炔衍生物(15a, 15b)的加成反应能在无任何氧化剂和溶剂的存在下高效进行。