O-Directed free radical hydrostannation of the β-cyclopropyl propargyl alcohol 57 with stannanes and cat. Et₃B in THF/H₂O or PhMe/MeOH failed to deliver any of the expected products of α-stannylvinyl cation capture. Instead only α-stannyl-β-cyclopropylvinyl radical intermediates were detected, which underwent fast H-atom abstraction and/or cyclopropane ring-opening as a result of eliminative β-scission. A second alkynol probe 23 was also studied in this O-directed free radical hydrostannation process. It gave rise to an α:β stannyl radical addition regiochemistry that changed markedly in favor of the α-adduct (26) when the reaction was conducted at high stannane concentrations. This outcome confirmed that O–Sn coordinative control must be responsible for the strong α-regiochemical preference of hydrostannations run at higher stannane concentrations, since a non-coordinative, electronically-controlled, stannyl radical addition would always give rise to a fixed and identical ratio of α:β-regioisomers. The formation of 27 further confirmed the exclusively free radical nature of these reactions.

β-环丙基炔丙醇57与锡烷和Cat的O定向自由基氢化。在THF / H ₂ O或PhMe / MeOH中的Et ₃ B未能传递任何预期的α-锡烷基乙烯基阳离子捕获产物。取而代之的是，仅检测到α-锡烷基-β-环丙基乙烯基自由基中间体，这些中间体由于消除了β断裂而经历了快速的H原子提取和/或环丙烷开环。在该O取向的自由基氢化过程中还研究了第二炔醇探针23。它引起了α：β苯乙烯基自由基加成区域化学反应，显着改变，有利于α加合物（26当在高锡烷浓度下进行反应时。这一结果证实，O-Sn协调控制必须对锡烷浓度较高时运行的锡烷基锡的强烈α-区域化学偏好负责，因为非协调，电子控制的苯乙烯基自由基的添加总是会产生固定且相同的比率α：β-区域异构体的组成。27的形成进一步证实了这些反应的完全自由基性质。