74213-48-2Relevant academic research and scientific papers
Hydroboration of Terminal Alkenes and trans-1,2-Diboration of Terminal Alkynes Catalyzed by a Manganese(I) Alkyl Complex
Kirchner, Karl,St?ger, Berthold,Veiros, Luis F.,Weber, Stefan,Zobernig, Daniel
supporting information, p. 24488 - 24492 (2021/10/19)
A MnI-catalyzed hydroboration of terminal alkenes and a 1,2-diboration of terminal alkynes with pinacolborane (HBPin) is described. For alkenes, anti-Markovnikov hydroboration takes place; for alkynes the reaction proceeds with excellent trans-1,2-selectivity. The most active pre-catalyst is bench-stable alkyl bisphosphine MnI complex fac-[Mn(dippe)(CO)3(CH2CH2CH3)]. The catalytic process is initiated by migratory insertion of a CO ligand into the Mn–alkyl bond to yield an acyl intermediate, which undergoes B?H bond cleavage of HBPin (for alkenes) and rapid C?H bond cleavage (for alkynes), forming the active MnI boryl and acetylide catalysts [Mn(dippe)(CO)2(BPin)] and [Mn(dippe)(CO)2(C≡CR)], respectively. A broad variety of aromatic and aliphatic alkenes and alkynes was efficiently and selectively borylated. Mechanistic insights are provided based on experimental data and DFT calculations revealing that an acceptorless reaction is operating involving dihydrogen release.
Copper-Photocatalyzed Hydroboration of Alkynes and Alkenes
Zhong, Mingbing,Gagné, Yohann,Hope, Taylor O.,Pannecoucke, Xavier,Frenette, Mathieu,Jubault, Philippe,Poisson, Thomas
supporting information, p. 14498 - 14503 (2021/05/21)
The photocatalytic hydroboration of alkenes and alkynes is reported. The use of newly-designed copper photocatalysts with B2Pin2 permits the formation a boryl radical, which is used for hydroboration of a large panel of alkenes and a
Photocatalyzed E→Z Contra-thermodynamic Isomerization of Vinyl Boronates with Binaphthol
Brégent, Thibaud,Bouillon, Jean-Philippe,Poisson, Thomas
supporting information, p. 13966 - 13970 (2021/08/25)
The photocatalytic contra-thermodynamic E→Z isomerization of vinyl boronates by using a binaphthol catalyst is disclosed. The reaction, based on the transient formation of a suitable chromophore with a BINOL derivative as the catalyst, allowed geometrical isomerization in good-to-excellent Z/E ratio and excellent-to-quantitative yields. The mechanism of this E→Z contra-thermodynamic isomerization was studied, and the formation of a transient chromophore species is suggested.
(Z)-Selective Hydroboration of Terminal Alkynes Catalyzed by a PSP-Pincer Rhodium Complex
Lyu, Yanzong,Toriumi, Naoyuki,Iwasawa, Nobuharu
supporting information, p. 9262 - 9266 (2021/11/30)
A highly (Z)-selective hydroboration of terminal alkynes was achieved using a thioxanthene-based PSP-pincer rhodium catalyst. This hydroboration exhibited good chemoselectivity toward alkynes over carbonyl compounds such as ketones and aldehydes. The mechanistic studies indicated the involvement of rhodium-vinylidene intermediates, and the high (Z)-selectivity could be attributed to the rigid and electron-rich nature of the PSP-rhodium catalyst.
Stereoselective Bromoboration of Acetylene with Boron Tribromide: Preparation and Cross-Coupling Reactions of (Z)-Bromovinylboronates
Polá?ek, Jan,Paciorek, Jan,Sto?ek, Jakub,Semrád, Hugo,Munzarová, Markéta,Mazal, Ctibor
, p. 6992 - 7000 (2020/06/05)
The mechanism of acetylene bromoboration in neat boron tribromide was studied carefully by means of experiment and theory. Besides the syn-addition mechanism through a four-center transition state, radical and polar anti-addition mechanisms are postulated, both triggered by HBr, which is evidenced also to take part in the Z/E isomerization of the product. The proposed mechanism is well supported by ab initio calculations at the MP2/6-31+G? level with Ahlrichs' SVP all-electron basis for Br. Implicit solvation in CH2Cl2 has been included using the PCM and/or SMD continuum solvent models. Comparative case studies have been performed involving the B3LYP/6-31+G? with Ahlrichs' SVP for Br and MP2/Def2TZVPP levels. The mechanistic studies resulted in development of a procedure for stereoselective bromoboration of acetylene yielding E/Z mixtures of dibromo(bromovinyl)borane with the Z-isomer as a major product (up to 85%). Transformation to the corresponding pinacol and neopentyl glycol boronates and stereoselective decomposition of their E-isomer provided pure (Z)-(2-bromovinyl)boronates in 57-60% overall yield. Their reactivity in a Negishi cross-coupling reaction was tested. An example of the one-pot reaction sequence of Negishi and Suzuki-Miyaura cross-couplings for synthesis of combretastatin A4 is also presented.
Z-Selective Alkyne Functionalization Catalyzed by a trans-Dihydride N-Heterocyclic Carbene (NHC) Iron Complex
De Ruiter, Graham,Fridman, Natalia,Garhwal, Subhash
supporting information, p. 13817 - 13821 (2020/10/09)
The Z-selective functionalization of terminal alkynes is a useful transformation in organic chemistry and mainly catalyzed by noble metals. Here, we present the Z-selective hydroboration of terminal alkynes catalyzed by a stable trans-dihydride iron compl
Dearomatization and Functionalization of Terpyridine Ligands Leading to Unprecedented Zwitterionic Meisenheimer Aluminum Complexes and Their Use in Catalytic Hydroboration
Zhang, Guoqi,Wu, Jing,Zeng, Haisu,Neary, Michelle C.,Devany, Matthew,Zheng, Shengping,Dub, Pavel A.
, p. 874 - 884 (2019/01/14)
This paper reports the first example of dearomatization of ubiquitous terpyridine (tpy) ligands via 2′/6′-, 3′/5′-, or 4′-selective alkylation of the central pyridine ring. The reaction is mediated by the most abundant metal in the Earth's crust, aluminum (Al), and depending on the conditions employed, exhibits ionic or radical character as suggested by experimental and computational analysis. In the latter case, intermediate formation of an AlIII complex supported by π-radical monoanionic ligand (tpy?)1- is apparent. The 3′/5′-alkylation leads to unprecedented zwitterionic Meisenheimer AlIII complexes, which were identified as efficient precatalysts for the selective hydroboration of C=O and C-C functionalities. Turnover numbers (TONs) up to ～1000 place the corresponding complexes in the category of the most efficient Al catalysts reported to date for the title reaction. The acquired data suggest that aluminum monohydrides, or more likely dihydrides, could be relevant catalytic species. Alternatively, one can also imagine a mechanistic scenario in which the dearomatized "chemically noninnocent" ligand acts as hydride donor, and a detailed investigation of this is warranted in the future.
Stereoselective Synthesis of Vinylboronates by Rh-Catalyzed Borylation of Stereoisomeric Mixtures
Li, Shenhuan,Li, Jie,Xia, Tianlai,Zhao, Wanxiang
supporting information, p. 462 - 468 (2019/03/28)
The stereoselective preparation of vinylboronates via rhodium-catalyzed borylation of E/Z mixtures of vinyl actetates is described, and this method was also extended to synthesis of vinyldiboronates. These transformations feature high functional group compatibility and mild reaction conditions. Control experiments support a mechanism that involved a Rh-catalyzed borylation-isomerization sequence. The isomerization of (Z)-vinylboronates to (E)-isomers was also demonstrated.
Synthesis of Functionalized 1,3-Butadienes via Pd-Catalyzed Cross-Couplings of Substituted Allenic Esters in Water at Room Temperature
Lippincott, Daniel J.,Linstadt, Roscoe T. H.,Maser, Michael R.,Gallou, Fabrice,Lipshutz, Bruce H.
, p. 4719 - 4722 (2018/08/23)
An environmentally responsible, mild method for the synthesis of functionalized 1,3-butadienes is presented. It utilizes allenic esters of varying substitution patterns, as well as a wide range of boron-based nucleophiles under palladium catalysis, generating sp-sp2, sp2-sp2, and sp2-sp3 bonds. Functional group tolerance measured via robustness screening, along with room temperature and aqueous reaction conditions highlight the methodology's breadth and potential utility in synthesis.
Contra-Thermodynamic, Photocatalytic E→Z Isomerization of Styrenyl Boron Species: Vectors to Facilitate Exploration of Two-Dimensional Chemical Space
Molloy, John J.,Metternich, Jan B.,Daniliuc, Constantin G.,Watson, Allan J. B.,Gilmour, Ryan
supporting information, p. 3168 - 3172 (2018/02/26)
Designing strategies to access stereodefined olefinic organoboron species is an important synthetic challenge. Despite significant advances, there is a striking paucity of routes to Z-α-substituted styrenyl organoborons. Herein, this strategic imbalance is redressed by exploiting the polarity of the C(sp2)?B bond to activate the neighboring π system, thus enabling a mild, traceless photocatalytic isomerization of readily accessible E-α-substituted styrenyl BPins to generate the corresponding Z-isomers with high fidelity. Preliminary validation of this contra-thermodynamic E→Z isomerization is demonstrated in a series of stereoretentive transformations to generate Z-configured trisubstituted alkenes, as well as in a concise synthesis of the anti-tumor agent Combretastatin A4.
