Trang Thi Thu Ngo Koichi Mikami, Silyl Effects on 1,3-Diphospha- cyclobutane-2,4-diyl: Ring-Opening of Tetra- hydrofuran and Promotion of Reductive P-C Cleavage
Trang Thi Thu Ngo Koichi Mikami, Silyl Effects on 1,3-Diphospha- cyclobutane-2,4-diyl: Ring-Opening of Tetra- hydrofuran and Promotion of Reductive P-C Cleavage
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Trang Thi Thu Ngo Koichi Mikami，甲硅烷基对 1,3-Diphospha- cyclobutane-2,4-diyl 的影响：四氢呋喃的开环和促进还原性 P-C 裂解
DOI：
10.1002/asia.201300564
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发表时间：
2013
期刊：
影响因子：
--
通讯作者：
Shigekazu Ito
中科院分区：
文献类型：
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作者：
K. Kawai;T. Majima;藤井郁雄;Shigekazu Ito
环丁烷二基的磷同系物（图1a）在室温下是可分离的单线态双自由基物种。由于其独特的电子性质，我们期望它成为开发新型功能材料的有用分子实体。[1-3]Niecke及其同事利用热稳定的2，4-二氯-1，3-双（2，4，6-三叔丁基苯基）-1，3-二磷杂环丁烷-2，4-二基（由大体积的二氯亚甲基膦[1]制备）来制备具有例如卡宾、自由基和离子部分的结构奇异的有机磷化合物。[4]另一方面，在室温下稳定的1，3-二磷杂环丁烯-4-基阴离子1（图1 B; Mes*= 2，4，6-三叔丁基苯基）也可以用作制备耐空气的P-杂环单线态双自由基的通用试剂。[5]研究了由1制备的高度稳定的双自由基衍生物的物理化学性质。迄今为止，1的烷基化、[5，6a-f，h，7]全氟烷基化、[6c]酰化、[6a]硫代烷基化和硫代芳基化[6 g]已经产生了空气稳定的1，3-二磷杂环丁烷-2，4-二基。此外，还证明了1的单电子氧化，产生对空气不敏感的P-杂环单价基。[8]然而，P-杂环阴离子1可以替代地充当良好的离去基团[7a]，并且具有通过与某些亲电试剂反应产生不期望的产物的倾向。因此，1的反应性需要进一步研究，以开发新的功能化的P-杂环双自由基。此外，用于合成1的新程序有望进一步研究P-杂环双自由基，这些自由基很难通过既定的方案制备。我们利用甲硅烷基研究外来磷杂环的化学。我们还公开了1a（G= tBu）、甲硅烷基卤化物和四氢呋喃（THF）的三组分反应，这导致了新的稳定的P-杂环双自由基。甲硅烷基和特定的P-杂环系统之间的中间体P2 Si键激活了环醚结构的开环，这有效地稳定了1a。此外，我们对三组分反应的产物的反应性研究揭示了在用叔丁基锂处理时意外的区域选择性P2 O3 C键裂解反应，以产生相应的1，3-二磷杂环丁烯-4-基阴离子1。我们应用这种新的协议，以制备1途中几个新的可分离的P-杂环双自由基。我们还研究了P-杂环双自由基的氧化还原性质，以了解很少使用的取代基效应。我们在40 ℃下用甲硅烷基三氟甲磺酸酯处理1-叔丁基-2，4-双（2，4，6-三叔丁基苯基）-1，3-二磷杂环丁烯-4-基阴离子（1a），该阴离子由磷炔2和叔丁基锂（0.5当量）在THF中制备（方案1，路径A; TMS= SiMe 3，TBS= SiMe 2 tBu）。挥发性物质蒸发后，用己烷萃取，我们得到空气稳定的深蓝色结晶化合物3a和3b（分别为77%和78%）。虽然我们最初预计形成[a]教授博士S。Ito，TTT Ngo，Prof. Dr. K.东京工业大学大学院理工学研究科三上应用化学系东京都目黑大冈山2-12-1邮编：152-8552传真：（+ 81）3-5734 2143
The phosphorus congener of cyclobutanediyl (Figure 1a) is an isolable singlet biradical species at room temperature. We expect it to be a useful molecular entity for developing novel functional materials because of its unique electronic properties.[1–3] Niecke and co-workers have utilized thermally stable 2, 4-dichloro-1, 3-bis (2, 4, 6-tri-tert-butylphenyl)-1, 3-diphosphacyclobutane-2, 4-diyl, prepared from a bulky dichloromethylenephosphine,[1] to prepare structurally exotic organophosphorus compounds that have, for example, carbene, radical, and ionic moieties.[4] On the other hand, the 1, 3-diphosphacyclobuten-4-yl anion 1 (Figure 1 b; Mes*= 2, 4, 6-tri-tert-butylphenyl), which is stable at room temperature, can also be employed as a versatile reagent for preparing air-tolerant P-heterocyclic singlet biradicals.[5] The physicochemical properties of highly stabilized biradical derivatives prepared from 1 have been investigated. Alkylation,[5, 6a–f, h, 7] perfluoroalkylation,[6c] acylation,[6a] thioalkylation, and thioarylation [6g] of 1 have thus far yielded air-stable 1, 3-diphosphacyclobutane-2, 4-diyls. Furthermore, one-electron oxidation of 1, which yields an air-insensitive P-heterocyclic monoradical, has also been demonstrated.[8] However, the P-heterocyclic anion 1 can instead act as a good leaving group [7a] and has a propensity to yield undesirable products through reaction with certain electrophiles. Therefore, the reactivity of 1 requires further investigation to develop novel functionalized P-heterocyclic biradicals. Additionally, novel procedures for synthesizing 1 hold promise for further research with respect to P-heterocyclic biradicals that have been difficult to prepare by established protocols. We utilized silyl groups to investigate the chemistry of exotic phosphorus heterocycles. We also disclose a threecomponent reaction of 1a (G= tBu), silyl halide, and tetrahydrofuran (THF), which leads to novel stable P-heterocyclic biradicals. The intermediate PÀSi linkage between the silyl group and the particular P-heterocyclic system activates ring-opening of the cyclic ether structure, which effectively stabilizes 1a. Furthermore, our reactivity studies on the products of the three-component reactions revealed an unexpected regioselective PÀC bond cleavage reaction upon treatment with tert-butyllithium to generate the corresponding 1, 3-diphosphacyclobuten-4-yl anion 1. We applied this novel protocol to prepare 1 en route to several novel isolable P-heterocyclic biradicals. We also investigated the redox properties of the P-heterocyclic biradicals to understand the substituent effects that have rarely been employed. We treated 1-tert-butyl-2, 4-bis (2, 4, 6-tri-tert-butylphenyl)-1, 3-diphosphacyclobuten-4-yl anion (1a), prepared from phosphaalkyne 2 and tert-butyllithium (0.5 equiv) in THF, with silyl triflates at 408C (Scheme 1, path A; TMS= SiMe3, TBS= SiMe2tBu). After evaporation of the volatile materials and extraction with hexane, we obtained the air-stable deep-blue crystalline compounds 3a and 3b (77% and 78%, respectively). Although we initially expected formation of [a] Prof. Dr. S. Ito, TTT Ngo, Prof. Dr. K. Mikami Department of Applied Chemistry Graduate School of Science and Engineering Tokyo Institute of Technology 2-12-1, Ookayama, Meguro, Tokyo 152-8552 (Japan) Fax:(+ 81) 3-5734 2143