Department of Chemistry, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States.
Universidad de Alcalá, Department of Analytical Chemistry, Physical Chemistry, and Chemical Engineering, Ctra. Madrid-Barcelona Km. 33,600, Madrid 28871, Spain.
J Am Chem Soc. 2017 Aug 9;139(31):10822-10831. doi: 10.1021/jacs.7b05464. Epub 2017 Jul 27.
Dibenzo-7-phosphanorbornadiene compounds, RPA (A = CH or anthracene), are investigated as phosphinidene sources upon thermally induced (70-90 °C) anthracene elimination. Analysis of substituent effects reveals that π-donating dialkylamide groups are paramount to successful phosphinidene transfer; poorer π-donors give reduced or no transfer. Substituent steric bulk is also implicated in successful transfer. Molecular beam mass spectrometry (MBMS) studies of each derivative reveal dialkylamide derivatives to be promising precursors for further gas-phase spectroscopic studies of phosphinidenes; in particular, we present evidence of direct detection of the dimethylamide derivative, [MeN═P]. Kinetic investigations of PrNPA thermolysis in 1,3-cyclohexadiene and/or benzene-d are consistent with a model of unimolecular fragmentation to yield free phosphinidene [PrN═P] as a transient reactive intermediate. This conclusion is probed by density functional theory (DFT) calculations, which favored a mechanistic model featuring free singlet aminophosphinidenes. The breadth of phosphinidene acceptors is expanded to unsaturated substrates beyond 1,3-dienes to include olefins and alkynes; this provides a new synthetic route to valuable amino-substituted phosphiranes and phosphirenes, respectively. Stereoselective phosphinidene transfer to olefins is consistent with singlet phosphinidene reactivity by analogy with the Skell hypothesis for singlet carbene addition to olefins.
二苯并-7-磷杂降冰片二烯化合物，RPA（A=CH 或蒽），作为磷烯源，在热诱导（70-90°C）的蒽消除反应中被研究。取代基效应的分析表明，给电子的二烷基酰胺基团对于成功的磷烯转移至关重要；较差的给电子基团会导致转移减少或不发生。取代基的空间位阻也与成功的转移有关。对每个衍生物的分子束质谱（MBMS）研究表明，二烷基酰胺衍生物是进一步进行气相磷烯光谱研究的有前途的前体；特别是，我们提供了直接检测二甲酰胺衍生物[MeN═P]的证据。PrNPA 在 1,3-环己二烯和/或苯-d 中的热解的动力学研究与单分子碎裂的模型一致，生成游离磷烯[PrN═P]作为瞬态反应性中间体。这一结论通过密度泛函理论（DFT）计算得到了证实，DFT 计算有利于采用游离单重态氨基磷烯的机理模型。磷烯受体的范围扩大到了不饱和底物，包括烯烃和炔烃，超过了 1,3-二烯；这分别为有价值的氨基取代的磷杂环戊烷和磷杂环戊二烯提供了新的合成途径。与烯烃中单重态卡宾加成的 Skell 假设类似，烯烃的立体选择性磷烯转移与单重态磷烯的反应性一致。
