32400-07-0Relevant academic research and scientific papers
Cycloalkylmethyl Radicals. 5. 6- to 15-Membered Rings: EPR Studies of Ring Conformations and Stereodynamics
Ingold, K. U.,Walton, J. C.
, p. 6937 - 6943 (1987)
Cycloalkylmethyl radicals having 7- to 15-membered rings (excluding cyclotetradecylmethyl) have been generated and examined by EPR spectroscopy.All the cycloalkylmethyl radicals from the 9-membered ring upward show two distinguishable conformers, though there may be additional conformers present with cyclodecylmethyl and cyclopentadecylmethyl radicals.All the cycloalkylmethyl radicals from the 10-membered ring upward have one conformer, the quasi-equatorial, QE, with an Hβ hfs in the range 27.7-32.0 G at 140 K and one conformer, the quasi-axial, QA, with an Hβ hfs in the range 38.3-40.4 G at 140 K.The QE and QA conformers have been assigned to species in which the CH2. group occupies "outer-edge" and "corner" sites, respectively, in the preferred conformations of the cycloalkanes.The EPR results indicated that the preferred conformations of the C9, C10, C11, C12, C13, and C15 rings were , , , , , and , respectively.Arrhenius parameters for ring-atom site exchange in the cycloalkylmethyl radicals have been determined from the exchange broadening in the EPR spectra.These EPR barriers are compared with literature data on cycloalkane free energy barriers measured by NMR and enthalpic barriers estimated by force field and related methods.
Reactivity studies of a zirconium methylidene complex: Group transfer and methylenation reactions
Kurogi, Takashi,Kamitani, Masahiro,Manor, Brian C.,Carroll, Patrick J.,Mindiola, Daniel J.
, p. 74 - 79 (2017)
The zirconium methylidene complex (PNP)-Zr=CH2(OAr) (1; PNP = N[2-PiPr2-4-methylphenyl]2-, Ar = 2,6-iPr2C6H3), prepared from photolysis of (PNP)Zr-(CH3)2(OAr), can engage in incomplete and complete methylidene group transfer reactions with CO, CDCl3, cyclododecanone, and benzophenone. When CO was treated with 1, methylenation occurred via the putative metalloketene adduct [(PNP)Zr(OCCH2)(OAr)], which ultimately afforded t h e C-C coupled eno l a t e dimer [(PNP)Zr-(OAr)]2(OCH2C=CCH2O) (2). Addition of CDCl3 to 1 rapidly resulted in formation of (PNP)ZrCl2(OAr) (3) along with liberation of d1-vinyl chloride, H2C=CDCl. Complex 3 could be readily prepared independently from (PNP)ZrCl3 and 1 equiv of NaOAr. Wittig reactivity was observed between 1 and cyclododecanone to afford methylenecyclododecane. Similarly, treating 1 with the ketone OCPh2 resulted in methylenation of the ortho position followed by tautomerization to produce the chelated alkyloxide complex (PNP)Zr(OAr)[OCHPh(C6H4)-CH2] (4). In addition to the isolation of 4, complex 1 also engages in a cross-metathesis reaction involving the methylidene and ketone oxygen of benzophenone, as well as in olefin metathesis involving the formed olefin H2C=CPh2. Complexes 2-4 have been fully characterized, including solid-state structural analysis, and proposed mechanisms for the formation of species such as 2-4 are presented and discussed.
Dearomative Cyclopropanation of Naphthols via Cyclopropene Ring-Opening
Baker, Rachel J.,Ching, Justin,Franzoni, Ivan,Hou, Teh Ren,Lautens, Mark
supporting information, (2022/01/13)
The dearomatization of 2-naphthols represents a simple method for the construction of complex 3D structures from simple planar starting materials. We describe a cyclopropanation of 2-naphthols that proceeds via cyclopropene ring-opening using rhodium and acid catalysis under mild conditions. The vinyl cyclopropane molecules were formed with high chemoselectivity and scalability, which could be further functionalized at different sites. Both computational and experimental evidence were used to elucidate the reaction mechanism.
Titanium and Cobalt Bimetallic Radical Redox Relay for the Isomerization of N -Bz Aziridines to Allylic Amides
Wood, Devin P.,Guan, Weiyang,Lin, Song
supporting information, p. 4213 - 4220 (2021/08/10)
Herein a bimetallic radical redox-relay strategy is employed to generate alkyl radicals under mild conditions with titanium(III) catalysis and terminated via hydrogen atom transfer with cobalt(II) catalysis to enact base-free isomerizations of N-Bz aziridines to N-Bz allylic amides. This reaction provides an alternative strategy for the synthesis of allylic amides from alkenes via a three-step sequence to accomplish a formal transpositional allylic amination.
Oxidative Cleavage of Alkenes by O2with a Non-Heme Manganese Catalyst
Bennett, Elliot L.,Brookfield, Adam,Guan, Renpeng,Huang, Zhiliang,Mcinnes, Eric J. L.,Robertson, Craig M.,Shanmugam, Muralidharan,Xiao, Jianliang
supporting information, p. 10005 - 10013 (2021/07/19)
The oxidative cleavage of C═C double bonds with molecular oxygen to produce carbonyl compounds is an important transformation in chemical and pharmaceutical synthesis. In nature, enzymes containing the first-row transition metals, particularly heme and non-heme iron-dependent enzymes, readily activate O2 and oxidatively cleave C═C bonds with exquisite precision under ambient conditions. The reaction remains challenging for synthetic chemists, however. There are only a small number of known synthetic metal catalysts that allow for the oxidative cleavage of alkenes at an atmospheric pressure of O2, with very few known to catalyze the cleavage of nonactivated alkenes. In this work, we describe a light-driven, Mn-catalyzed protocol for the selective oxidation of alkenes to carbonyls under 1 atm of O2. For the first time, aromatic as well as various nonactivated aliphatic alkenes could be oxidized to afford ketones and aldehydes under clean, mild conditions with a first row, biorelevant metal catalyst. Moreover, the protocol shows a very good functional group tolerance. Mechanistic investigation suggests that Mn-oxo species, including an asymmetric, mixed-valent bis(μ-oxo)-Mn(III,IV) complex, are involved in the oxidation, and the solvent methanol participates in O2 activation that leads to the formation of the oxo species.
Direct Synthesis of Unprotected 2-Azidoamines from Alkenes via an Iron-Catalyzed Difunctionalization Reaction
Makai, Szabolcs,Falk, Eric,Morandi, Bill
supporting information, p. 21548 - 21555 (2021/01/11)
Unprotected, primary 2-azidoamines are versatile precursors to vicinal diamines, which are among the most common motifs in biologically active compounds. Herein, we report their operationally simple synthesis through an iron-catalyzed difunctionalization of alkenes. A wide array of alkene substrates are tolerated, including complex drug-like molecules and a tripeptide. Facile derivatizations of the azidoamine group demonstrate the versatility of this masked diamine motif in chemoselective, orthogonal transformations. Applications of the methodology in the concise synthesis of RO 20-1724 as well as in the formal total syntheses of both (±)-hamacanthin B and (±)-quinagolide further demonstrate the broad synthetic potential of this highly functional-group-tolerant reaction.
Rhodium-Catalyzed Intermolecular Cyclopropanation of Benzofurans, Indoles, and Alkenes via Cyclopropene Ring Opening
Jeyaseelan, Rubaishan,Lautens, Mark,Ross, Rachel J.
supporting information, (2020/06/29)
The generation of metal carbenoids via ring opening of cyclopropenes by transition metals offers a simple entry into highly reactive intermediates. Herein, we describe a diastereoselective intermolecular rhodium-catalyzed cyclopropanation of heterocycles and alkenes using cyclopropenes as carbene precursors with a low loading of a commercially available rhodium catalyst. The reported method is scalable and could be performed with catalyst loadings as low as 0.2 mol %, with no impact to the reaction yield or selectivity.
Stereoselective Synthesis of Vinylcyclopropa[ b]indolines via a Rh-Migration Strategy
Guo, Pan,Sun, Wangbin,Liu, Yu,Li, Yong-Xin,Loh, Teck-Peng,Jiang, Yaojia
supporting information, p. 5978 - 5983 (2020/08/05)
A mild rhodium catalytic system has been developed to synthesize vinylcyclopropa[b]indolines through cyclopropanation of indoles with vinyl carbenoids generated from ring opening of cyclopropenes in situ. By employing a Rh-migration strategy, the products can be obtained with good to excellent E:Z ratios (≤99:1) and complete diastereoselectivity (≤99:1). This method is easy, has a low catalyst loading, and works for a broad range of functionalities.
Synthesis of Functionalized α-Vinyl Aldehydes from Enaminones
Chen, Jie,Guo, Pan,Zhang, Jianguo,Rong, Jiaxin,Sun, Wangbin,Jiang, Yaojia,Loh, Teck-Peng
supporting information, p. 12674 - 12679 (2019/08/07)
An efficient RhII-catalyzed synthesis of functionalized α-vinyl aldehydes with high E/Z stereoselectivity was developed. The reaction mediates the cyclopropanation of enaminones with vinyl carbenoids that are generated from cyclopropenes in situ to give the aminocyclopropane intermediates. Selective C?C bond cleavage of the cyclopropane intermediates leads to formation of α-vinyl aldehyde derivatives with high E/Z selectivity. This method proceeds at room temperature under very mild reaction conditions and works with a broad substrate scope.
Mild Ring-Opening 1,3-Hydroborations of Non-Activated Cyclopropanes
Wang, Di,Xue, Xiao-Song,Houk, Kendall N.,Shi, Zhuangzhi
supporting information, p. 16861 - 16865 (2018/11/27)
The Brown hydroboration reaction, first reported in 1957, is the addition of B?H across an olefin in an anti-Markovnikov fashion. Here, we solved a long-standing problem on mild 1,3-hydroborations of non-activated cyclopropanes. A three-component system including cyclopropanes, boron halides, and hydrosilanes has been developed for borylative ring-opening of cyclopropanes following the anti-Markovnikov rule, under mild reaction conditions. Density functional theory (M06-2X) calculations show that the preferred pathway involves a cationic boron intermediate which is quenched by hydride transfer from the silane.
