26461-03-0Relevant articles and documents
Remote, Diastereoselective Cobalt-Catalyzed Alkene Isomerization-Hydroboration: Access to Stereodefined 1,3-Difunctionalized Indanes
Léonard, Nadia G.,Palmer, W. Neil,Friedfeld, Max R.,Bezdek, Máté J.,Chirik, Paul J.
, p. 9034 - 9044 (2019)
The remote, diastereoselective hydroboration of 2- and 3-substituted indenes with a 2,2′:6′,2″-terpyridine cobalt alkyl precatalyst is described that maintains high regio- and stereoselectivity independent of the starting position of the alkene. Several 1,2- and 1,3-disubstituted indanyl boronate esters were obtained with exclusive (>20:1 dr) selectivity for the trans diastereomer including synthetically versatile, stereodefined diboron derivatives. Alkene isomerization by a putative cobalt hydride intermediate precedes carbon-boron bond formation, leading to the observed regioselectivity for boron incorporation at the unsubstituted C(sp3)-H benzylic site. The regio- and diastereoselectivity of the transformation were maintained independent of the starting position of the alkene, as demonstrated by hydroboration of three isomers of methyl-substituted indene. Deuterium-labeling experiments support rapid and reversible insertion and β-hydride elimination to isomerize 3-methylindene and 1-exo-methylene-indane, accounting for the isotopic distribution observed in the products. Mechanistic studies, including stoichiometric experiments, density functional theory calculations, and kinetic analysis, support a mechanism in which 2,3-alkene insertion into a cobalt hydride intermediate determines both the regio- and diastereoselectivity of the catalytic reaction. Synthetic applications of the indanyl boronate esters were demonstrated through the elaboration of the products to several examples of 1,3-disubstituted indanes, important carbocyclic structural motifs in both pharmacological and bioactive molecules.
N-Atom Deletion in Nitrogen Heterocycles
Cai, Wangshui,Guo, Ting,Li, Guigen,Lu, Hongjian,Qin, Haitao,Wang, Shuang
supporting information, p. 20678 - 20683 (2021/08/25)
Excising the nitrogen in secondary amines, and coupling the two residual fragments is a skeletal editing strategy that can be used to construct molecules with new skeletons, but which has been largely unexplored. Here we report a versatile method of N-atom excision from N-heterocycles. The process uses readily available N-heterocycles as substrates, and proceeds by N-sulfonylazidonation followed by the rearrangement of sulfamoyl azide intermediates, providing various cyclic products. Examples are provided of deletion of nitrogen from natural products, synthesis of chiral O-heterocycles from commercially available chiral β-amino alcohols, formal inert C?H functionalization through a sequence of N-directed C?H functionalization and N-atom deletion reactions in which the N-atom can serve as a traceless directing group.
Skeletal editing through direct nitrogen deletion of secondary amines
Kennedy, Sean H.,Dherange, Balu D.,Berger, Kathleen J.,Levin, Mark D.
, p. 223 - 227 (2021/05/19)
Synthetic chemistry aims to build up molecular complexity from simple feedstocks1. However, the ability to exert precise changes that manipulate the connectivity of the molecular skeleton itself remains limited, despite possessing substantial potential to expand the accessible chemical space2,3. Here we report a reaction that ‘deletes’ nitrogen from organic molecules. We show that N-pivaloyloxy-N-alkoxyamides, a subclass of anomeric amides, promote the intermolecular activation of secondary aliphatic amines to yield intramolecular carbon–carbon coupling products. Mechanistic experiments indicate that the reactions proceed via isodiazene intermediates that extrude the nitrogen atom as dinitrogen, producing short-lived diradicals that rapidly couple to form the new carbon–carbon bond. The reaction shows broad functional-group tolerance, which enables the translation of routine amine synthesis protocols into a strategy for carbon–carbon bond constructions and ring syntheses. This is highlighted by the use of this reaction in the syntheses and skeletal editing of bioactive compounds.
Bidentate NHC-Cobalt Catalysts for the Hydrogenation of Hindered Alkenes
Wei, Zeyuan,Wang, Yujie,Li, Yibiao,Ferraccioli, Raffaella,Liu, Qiang
, p. 3082 - 3087 (2020/10/02)
Herein, we report a series of easily accessible bidentate N-heterocyclic carbene (NHC) cobalt catalysts, which enable the hydrogenation of hindered alkenes under mild conditions. The four-coordinated bidentate NHC-Co(II) complexes were characterized by X-ray diffraction, elemental analysis, ESI-HRMS, and magnetic moment measurements, revealing a distorted-tetrahedral geometry and a high-spin configuration of the metal center. The activity of the in situ formed catalytic system, which was obtained from easily available NHC precursors, CoCl2, and NaHBEt3, was identical with those of well-defined NHC-cobalt catalysts. This highlights the potential utility of this reaction system.
Bisoxazoline-pincer ligated cobalt-catalyzed hydrogenation of alkenes
Ritz, Mikhaila D.,Parsons, Astrid M.,Palermo, Philip N.,Jones, William D.
supporting information, (2020/02/13)
The efficient and atom economical hydrogenation of alkenes using a novel bisoxazoline ligated cobalt complex has been developed. The hydrogenation of a variety of alkenes containing electron neutral and electron-donating groups proceeds in high yield, whi
Palladium Nanoparticles-Catalyzed Synthesis of Indanone Derivatives via Intramolecular Reductive Heck Reaction
Parveen, Naziya,Sekar, Govindasamy
, p. 4581 - 4595 (2019/09/03)
An efficient protocol for the straightforward, single-step synthesis of 3-aryl-1-indanones from 2′-iodochalcone via reductive Heck reaction using phosphine free, stable and reusable binaphthyl stabilized palladium nanoparticle (Pd-BNP) as a catalyst has been described. An immense array of substrate scope with electron-rich and deficient 2′-iodochalcones have been synthesized. Further derivatization of product indanones have been achieved successfully. The heterogeneous nature of the Pd-BNP has been validated by centrifugation test and mercury poisoning experiment. Pd-BNP has been successfully recycled up to 5 cycles without any significant loss in reaction yield and particle size of nanoparticles, confirmed by TEM analysis. (Figure presented.).
Synthesis of 1-aryl- benzocycloalkane derivatives via one-pot two-step reaction of benzocyclonone, tosylhydrazide, and arylboronic acid
Liu, Shijuan,Fang, Meitong,Yin, Dongni,Wang, Yanan,Liu, Lei,Li, Xiuying,Che, Guangbo
, p. 942 - 949 (2019/03/14)
A metal-free one-pot two-step reductive coupling reaction of benzocyclonone, tosylhydrazide, and arylboronic acid was developed for the formation of a C(sp3)–C(sp2) bond, which enabled the efficient synthesis of 1-aryl-benzocycloalkane compounds in moderate to good yields on a multi-gram scale. Moreover, five- and six-membered benzocyclic ketones are also suitable substrates for this reaction. Notably, this protocol was also found to be suitable for synthesizing 3-(3,4-dichlorophenyl)-2,3-dihydro-1H-inden-1-one, an important intermediate in the synthesis of indatraline.
Air-Stable α-Diimine Nickel Precatalysts for the Hydrogenation of Hindered, Unactivated Alkenes
Léonard, Nadia G.,Chirik, Paul J.
, p. 342 - 348 (2018/01/17)
Treatment of a mixture of air-stable nickel(II) bis(octanoate), Ni(O2CC7H15)2, and α-diimine ligand, iPrDI or CyADI (iPrDI = [2,6-iPr2-C6H3N=C(CH3)]2, CyADI = [C6H11N=C(CH3)]2) with pinacolborane (HBPin) generated a highly active catalyst for the hydrogenation of hindered, essentially unfunctionalized alkenes. A range of tri- and tetrasubstituted alkenes was hydrogenated and a benchtop procedure for the hydrogenation of 1-phenyl-1-cyclohexene on a multigram scale was demonstrated and represents an advance in catalyst activity and scope for the nickel-catalyzed hydrogenation of this challenging class of alkenes. Deuteration of 1,2-dimethylindene with the in situ-generated nickel catalyst with iPrDI exclusively furnished the 1,2-syn-d2-dimethylindane. With cyclic trisubstituted alkenes, such as 1-methyl-indene and methylcyclohexene, deuteration with the in situ generated nickel catalyst under 4 atm of D2 produced multiple deuterated isotopologues of the alkanes, signaling chain running processes that are competitive with productive hydrogenation. Stoichiometric studies, titration, and deuterium labeling experiments identified that the borane reagent served the dual role of reducing nickel(II) bis(carboxylate) to the previously reported nickel hydride dimer [(iPrDI)NiH]2 and increasing the observed hydrogenation activity. Performing the catalyst activation procedure with D2 gas and HBPin generated both HD and DBPin, establishing that the borane is involved in H2 activation as judged by 1H and 11B nuclear magnetic resonance spectroscopies.
Br?nsted Acid-Catalyzed Intramolecular Hydroarylation of β-Benzylstyrenes
Cai, Xiao,Keshavarz, Amir,Omaque, Justin D.,Stokes, Benjamin J.
supporting information, p. 2626 - 2629 (2017/05/24)
Using triphenylmethylium tetrakis(pentafluorophenyl)borate as a convenient Br?nsted acid precatalyst, β-(α,α-dimethylbenzyl)styrenes are shown to cyclize efficiently to afford a variety of new indanes that possess a benzylic quaternary center. The geminal dimethyl-containing quaternary center is proposed to be necessary to arm the substrate for cyclization through steric biasing.
Feedstocks to Pharmacophores: Cu-Catalyzed Oxidative Arylation of Inexpensive Alkylarenes Enabling Direct Access to Diarylalkanes
Vasilopoulos, Aristidis,Zultanski, Susan L.,Stahl, Shannon S.
supporting information, p. 7705 - 7708 (2017/06/20)
A Cu-catalyzed method has been identified for selective oxidative arylation of benzylic C-H bonds with arylboronic esters. The resulting 1,1-diarylalkanes are accessed directly from inexpensive alkylarenes containing primary and secondary benzylic C-H bonds, such as toluene or ethylbenzene. All catalyst components are commercially available at low cost, and the arylboronic esters are either commercially available or easily accessible from the commercially available boronic acids. The potential utility of these methods in medicinal chemistry applications is highlighted.
