School of Chemistry & Chemical Engineering, Huazhong University of Science & Technology, Luoyu Road 1037, 430074, Wuhan, P. R. China.
J Org Chem. 2012 Feb 3;77(3):1457-67. doi: 10.1021/jo202336y. Epub 2012 Jan 24.
Organotin-mediated regioselective protection has been extensively used in organic synthesis for many years. However, the mechanistic origin of the resulting regioselectivity is still not clear. By the comparison of the steric and stereoelectronic effects controlling the geometry of five-membered rings formed from neighboring group participation, from intramolecular acyl group migration, or from orthoester transesterification on pyranoside rings, a theory on the pattern resulting from the reaction with dibutyltin oxide is presented. It is thus suggested that the regioselectivity of organotin-mediated protection is controlled by analogous steric and stereoelectronic effects as in neighboring group participation and acyl group migration, mainly dependent on the stereoelectronic effects of the pyranoside itself, and not related to complex stannylene structures. An organotin protection mechanism is also suggested, emanating from steric and stereoelectronic effects, nucleophilicity, and organotin acyl migration.
有机锡介导的区域选择性保护在有机合成中已经得到了广泛的应用。然而，导致这种区域选择性的机制起源仍然不清楚。通过比较邻基参与、分子内酰基迁移或吡喃糖环上的邻苯二甲酸酯酯交换形成五元环的立体和立体电子效应，提出了一个关于与二丁基氧化锡反应产生的模式的理论。因此，有机锡介导的保护的区域选择性受类似的立体和立体电子效应控制，类似于邻基参与和酰基迁移，主要取决于吡喃糖本身的立体电子效应，而与复杂的锡烯结构无关。还提出了一种有机锡保护机制，源于立体和立体电子效应、亲核性和有机锡酰基迁移。
