280559-30-0Relevant articles and documents
Dramatic effect of Lewis acids on the rhodium-catalyzed hydroboration of olefins
Lata, Christopher J.,Crudden, Cathleen M.
, p. 131 - 137 (2010)
The addition of Lewis acids such as trispentafluoroboron as cocatalysts has been found to have a dramatic effect on the Rh-catalyzed hydroboration of olefins with pinacol borane. For example, aliphatic olefins do not react at all in noncoordinating solvents, but with the addition of 2% of B(C6F5)3, the reaction is complete in minutes. Similarly, the reaction of aromatic olefins with HBPin occurs slowly and nonselectively in the absence of B(C 6F5)3, but is accelerated and occurs more selectively in its presence. Preliminary mechanistic studies suggest that the B(C6F5)3 needs to be present throughout the course of the reaction, not just at the initiation stage, and implicate this species, along with THF, in the heterolytic cleavage of the B-H bond of HBPin.
Iron-Catalyzed Regioselective Alkenylboration of Olefins
Yu, Xiaolong,Zheng, Hongling,Zhao, Haonan,Lee, Boon Chong,Koh, Ming Joo
supporting information, p. 2104 - 2109 (2020/11/30)
The first examples of an iron-catalyzed three-component synthesis of homoallylic boronates from regioselective union of bis(pinacolato)diboron, an alkenyl halide (bromide, chloride or fluoride), and an olefin are disclosed. Products that bear tertiary or quaternary carbon centers could be generated in up to 87 % yield as single regioisomers with complete retention of the olefin stereochemistry. With cyclopropylidene-containing substrates, ring cleavage leading to trisubstituted E-alkenylboronates were selectively obtained. Mechanistic studies revealed reaction attributes that are distinct from previously reported alkene carboboration pathways.
Site-Fixed Hydroboration of Terminal and Internal Alkenes using BX3/iPr2NEt**
Cui, Xin,Hu, Chenyang,Li, Sida,Liu, Liu Leo,Wu, Lipeng,Zhang, Jiong
, p. 26238 - 26245 (2021/11/09)
An unprecedented and general hydroboration of alkenes with BX3 (X=Br, Cl) as the boration reagent in the presence of iPr2NEt is reported. The addition of iPr2NEt not only suppresses alkene polymerizat
Recyclable Copper Nanoparticles-Catalyzed Hydroboration of Alkenes and β-Borylation of α,β-Unsaturated Carbonyl Compounds with Bis(Pinacolato)Diboron
Shegavi, Mahadev L.,Saini, Suresh,Bhawar, Ramesh,Vishwantha, Meghana Desai,Bose, Shubhankar Kumar
supporting information, p. 2408 - 2416 (2021/03/16)
Nano-ferrite-supported Cu nanoparticles (Fe-dopamine-Cu NPs) catalyzed anti-Markovnikov-selective hydroboration of alkenes with B2pin2 is reported under mild reaction conditions. This protocol can be applied to a broad range of substrates with high functional group compatibility. In addition, we demonstrated the use of Fe-dopamine-Cu NPs as a catalyst for the β-borylation of α,β-unsaturated ketones and ester, providing alkylboronate esters in up to 98% yield. Reuse of the magnetically recyclable catalyst resulted in no significant loss of activity in up to five reaction runs for both systems. (Figure presented.).
Tropylium-Promoted Hydroboration Reactions: Mechanistic Insights Via Experimental and Computational Studies
Mai, Binh Khanh,Nguyen, Thanh Vinh,Ton, Nhan N. H.
, p. 9117 - 9133 (2021/07/19)
Hydroboration reaction of alkynes is one of the most synthetically powerful tools to access organoboron compounds, versatile precursors for cross-coupling chemistry. This type of reaction has traditionally been mediated by transition-metal or main group catalysts. Herein, we report a novel method using tropylium salts, typically known as organic oxidants and Lewis acids, to promote the hydroboration reaction of alkynes. A broad range of vinylboranes can be easily accessed via this metal-free protocol. Similar hydroboration reactions of alkenes and epoxides can also be efficiently catalyzed by the same tropylium catalysts. Experimental studies and DFT calculations suggested that the reaction follows an uncommon mechanistic pathway, which is triggered by the hydride abstraction of pinacolborane with tropylium ion. This is followed by a series ofin situcounterion-activated substituent exchanges to generate boron intermediates that promote the hydroboration reaction.
Metal-free photoinduced C(sp 3)–H borylation of alkanes
Shu, Chao,Noble, Adam,Aggarwal, Varinder K.
, p. 714 - 719 (2020/11/02)
Boronic acids and their derivatives are some of the most useful reagents in the chemical sciences1, with applications spanning pharmaceuticals, agrochemicals and functional materials. Catalytic C–H borylation is a powerful method for introducing these and other boron groups into organic molecules because it can be used to directly functionalize C–H bonds of feedstock chemicals without the need for substrate pre-activation1–3. These reactions have traditionally relied on precious-metal catalysts for C–H bond cleavage and, as a result, display high selectivity for borylation of aromatic C(sp2)–H bonds over aliphatic C(sp3)–H bonds4. Here we report a mechanistically distinct, metal-free borylation using hydrogen atom transfer catalysis5, in which homolytic cleavage of C(sp3)–H bonds produces alkyl radicals that are borylated by direct reaction with a diboron reagent. The reaction proceeds by violet-light photoinduced electron transfer between an N-alkoxyphthalimide-based oxidant and a chloride hydrogen atom transfer catalyst. Unusually, stronger methyl C–H bonds are borylated preferentially over weaker secondary, tertiary and even benzylic C–H bonds. Mechanistic studies indicate that the high methyl selectivity is a result of the formation of a chlorine radical–boron ‘ate?? complex that selectively cleaves sterically unhindered C–H bonds. By using a photoinduced hydrogen atom transfer strategy, this metal-free C(sp3)–H borylation enables unreactive alkanes to be transformed into valuable organoboron reagents under mild conditions and with selectivities that contrast with?those of established metal-catalysed protocols.
σ-Bond Hydroboration of Cyclopropanes
Arifin,Itami, Kenichiro,Kato, Hiroki,Kobayashi, Chisa,Kondo, Hiroki,Matsushita, Kaoru,Miyamura, Shin,Yamaguchi, Junichiro,Yokogawa, Daisuke
supporting information, p. 11306 - 11313 (2020/07/13)
Hydroboration of alkenes is a classical reaction in organic synthesis in which alkenes react with boranes to give alkylboranes with subsequent oxidation resulting in alcohols. The double bond (π-bond) of alkenes can be readily reacted with boranes owing to its high reactivity. However, the single bond (σ-bond) of alkanes has never been reacted. To pursue the development of σ-bond cleavage, we selected cyclopropanes as model substrates since they present a relatively weak σ-bond. Herein, we describe an iridium-catalyzed hydroboration of cyclopropanes, resulting in β-methyl alkylboronates. These unusually branched boronates can be derivatized by oxidation or cross-coupling chemistry, accessing "designer"products that are desired by practitioners of natural product synthesis and medicinal chemistry. Furthermore, mechanistic investigations and theoretical studies revealed the enabling role of the catalyst.
Metal-organic frameworks containing nitrogen-donor ligands for efficient catalytic organic transformations
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Page/Page column 49-51, (2020/06/03)
Metal-organic framework (MOFs) compositions based on nitrogen donor-based organic bridging ligands, including ligands based on 1,3-diketimine (NacNac), bipyridines and salicylaldimine, were synthesized and then post-synthetically metalated with metal precursors, such as complexes of first row transition metals. Metal complexes of the organic bridging ligands could also be directly incorporated into the MOFs. The MOFs provide a versatile family of recyclable and reusable single-site solid catalysts for catalyzing a variety of asymmetric organic transformations. The solid catalysts can also be integrated into a flow reactor or a supercritical fluid reactor.
Copper-Catalyzed Asymmetric Reduction of β,β-Disubstituted Alkenylboramides
Park, Yeji,Yun, Jaesook
supporting information, p. 8779 - 8782 (2019/11/03)
A highly enantioselective copper-catalyzed reduction of β,β-disubstituted alkenylboron compounds was developed using hydrosilane. The copper hydride catalyst coordinated with chiral Josiphos ligand efficiently discriminated β-geminal substituents to generate corresponding β-chiral alkylboramides with excellent enantioselectivities up to 99% ee. The enantioselective reduction protocol provides a facile approach to β-chiral alkylboron compounds with less sterically discriminating substituents and spans a wide substrate range including aryl-substituted borylalkenes with effective functional group tolerance.
Unlocking the catalytic potential of tris(3,4,5-trifluorophenyl)borane with microwave irradiation
Carden, Jamie L.,Gierlichs, Lukas J.,Wass, Duncan F.,Browne, Duncan L.,Melen, Rebecca L.
supporting information, p. 318 - 321 (2019/01/09)
The catalytic activity of tris(3,4,5-trifluorophenyl)borane has been explored in the 1,2-hydroboration reactions of unsaturated substrates. Under conventional conditions, the borane was found to be active only in the hydroboration of aldehyde, ketone and imine substrates, with alkenes and alkynes not being reduced effectively. The use of microwave irradiation on the other hand has permitted alkenes and alkynes to be hydroborated in good yields.
