Preparation of Ruthenium Azirinyl Complexes and Reversed Regiospecificity of the Carbonyl Insertion Reaction

Electrophilic addition of organic halides to [Ru]CN (1; [Ru] = Cp(PPh3)2Ru) gave the
cationic isocyanide complexes {[Ru]CNCH2R}X (R = CN, 2a; R = CHCH2, 2b; R = Ph,
2c), which reacted with base (n-Bu4NOH or n-Bu4NF) to give the three-membered-ring
azirinyl complexes. For the azirinyl complex with a phenyl group 3c, three isomers, assigned
as ruthenium 2H- and 1H-azirinyl complexes, are observed at −20 °C. Reaction of the methyl
isocyanoacetate complex {[Ru]C⋮NCH2COOMe}X (2d) with n-Bu4NOH causes hydrolysis
of the ester group to give the ruthenium oxazolone complex 4d. The insertion of the CO
group of acetone, aldehyde, ester, and amide into the C−C bond of the three-membered
azirinyl ring of 3a−c yields a variety of five-membered oxazolinyl complexes 5−7. The
regiospecificity of the insertion differs from that observed in the photochemically induced
carbonyl insertion in the organic azirine system. The diastereoselectivity in the formation
of 5−7 is controlled by steric effects. In the formation of the pentamethylcyclopentadienyl
oxazolinyl ruthenium complex 7a*, the intermediate 8a* is isolated before cyclization.
Molecular structures of 7a* and 8a* have been determined by single-crystal X-ray diffraction
analysis. Treatment of 7 with hydride gave [Ru]CN and alcohol.

将有机卤化物亲电加成至[Ru]CN（1；其中[Ru]代表Cp(PPh3)2Ru），得到阳离子型异氰配合物{[Ru]CNCH2R}X（R=氰基，2a；R=乙烯基，2b；R=苯基，2c）。该类配合物可与碱（四丁基氢氧化铵n-Bu4NOH或四丁基氟化铵n-Bu4NF）反应，生成三元环氮丙环基（azirinyl）配合物。对于带有苯基的氮丙环基配合物3c，在-20℃下可观测到三种异构体，分别归属为钌配位的2H-和1H-氮丙环基配合物。异氰乙酸甲酯配合物{[Ru]C≡NCH2COOMe}X（2d）与四丁基氢氧化铵反应时，其酯基发生水解，得到钌配位恶唑酮（oxazolone）配合物4d。将丙酮、醛、酯及酰胺的羰基插入至3a~c的三元氮丙环的C-C键中，可得到多种五元环恶唑啉基配合物5~7。该插入反应的区域选择性与有机氮丙环体系中光诱导羰基插入反应所观测到的区域选择性存在差异。5~7生成过程中的非对映选择性由空间位阻效应调控。在五甲基环戊二烯基恶唑啉基钌配合物7a*的合成过程中，环化前可分离得到中间体8a*。通过单晶X射线衍射分析确定了7a*与8a*的分子结构。用氢化物处理7，可得到[Ru]CN与醇。