Oxidizing Ability of a Series of (Tropon-2-ylimino)pnictoranes (Pnictogen = P, As, Sb, and Bi) toward Some Alcohols
作者:Yuhki Mitsumoto、Makoto Nitta
DOI:10.1246/bcsj.76.1029
日期:2003.5
In order to gain a better understanding of the oxidizing ability of a series of (tropon-2-ylimino)pnictoranes of the general structure Ph3M=NR (R = tropon-2-yl; M = P, As, Sb, and Bi), reactions were run with some alcohols such as benzopinacol (1,1,2,2-tetraphenyl-1,2-ethanediol), benzoin, cinnamyl alcohol, 1-phenylethanol, a mixture of cis- and trans-4-t-butylcyclohexanol, 2-phenylethanol, and 1-phenyl-1,3-propandiol. Iminophosphorane oxidized only benzopinacol to give benzophenone, while both arsorane and stiborane oxidized benzopinacol and benzoin to give benzophenone and benzil, respectively. On the other hand, iminobismuthorane has appreciable oxidizing ability, and reacted with the alcohols mentioned above, except the primary alcohol, to give the corresponding carbonyl compounds. Iminobismuthorane reacted with 1-phenyl-1,3-propandiol selectively to oxidize benzyl alcohol moiety, but not a primary alcohol moiety, to give 3-hydroxy-1-phenyl-1-propanone. Thus, the oxidizing ability of a series of (tropon-2-ylimino)pnictoranes is demonstrated to be in the order of iminophosphorane < iminoarsorane < iminostiborane < iminobismuthorane: the dipolar (degree of contribution of the Ph3M+–−NR canonical structure) and electrophilic character of pnictogen elements of a series of iminopnictoranes appear to increase their oxidizing ability when the pnictogen stands lower in the periodic table.
为了更好地理解一系列具有Ph3M=NR通式结构(R=2-亚芴基;M=P、As、Sb和Bi)的(2-亚芴基亚氨)膦烷类物质的氧化能力,我们进行了一些与醇类反应的实验,比如苯并匹考啉(1,1,2,2-四苯基-1,2-乙二醇),苯偶姻,肉桂醇,1-苯乙醇,顺-和反-4-叔丁基环己醇的混合物,2-苯乙醇,以及1-苯基-1,3-丙二醇。亚氨膦烷只将苯并匹考啉氧化生成了苯酞酮,而亚砷烷和锑烷都分别把苯并匹考啉和苯偶姻氧化生成了苯酞酮和苯偶酰。另一方面,亚铋锑烷具有显著的氧化能力,并且引发了上述提到的除一元醇以外的所有醇类,生成了相应的羰基化合物。亚铋锑烷与1-苯基-1,3-丙二醇选择性地反应,仅将苄醇基团氧化为3-羟基-1-苯基-1-丙酮,并未氧化一元醇基团。因此,一系列(2-亚芴基亚氨)膦烷类物质的氧化能力可证明是按照亚氨膦烷<亚砷烷<锑烷<铋锑烷的顺序排列:当膦元素在周期表中的位置越低,其偶极矩(Ph3M+–−NR经典结构贡献程度)和亲电特性会使得一系列亚氨膦烷的氧化能力增强。