2327-99-3Relevant academic research and scientific papers
Formation of Nucleophilic Allylboranes from Molecular Hydrogen and Allenes Catalyzed by a Pyridonate Borane that Displays Frustrated Lewis Pair Reactivity
Ahles, Sebastian,Averdunk, Arthur,Becker, Jonathan,Gellrich, Urs,Hasenbeck, Max
, p. 23885 - 23891 (2020)
Here we report the in situ generation of nucleophilic allylboranes from H2 and allenes mediated by a pyridonate borane that displays frustrated-Lewis-pair reactivity. Experimental and computational mechanistic investigations reveal that upon H2 activation, the covalently bound pyridonate substituent becomes a datively bound pyridone ligand. Dissociation of the formed pyridone borane complex liberates Piers borane and enables a hydroboration of the allene. The allylboranes generated in this way are reactive towards nitriles. A catalytic protocol for the formation of allylboranes from H2 and allenes and the allylation of nitriles has been devised. This catalytic reaction is a conceptually new way to use molecular H2 in organic synthesis.
Acid-catalyzed conversion of 7-ethynyl- and 7-vinyleyclohepta-1,3, 5-trienes to substituted benzene derivatives
Minegishi, Shinya,Kamada, Jun,Takeuchi, Ken'ichi,Komatsu, Koichi,Kitagawa, Toshikazu
, p. 3497 - 3504 (2003)
The acid-catalyzed rearrangement in THF/TFA (5:1, v/v) of cyclohepta-1,3,5-trienes containing an α,β-unsaturated substituent at C-7 was investigated. 7-Ethynylcyclohepta-1,3,5-triene (1a) and its 1,4-di-tert-butyl (1b), 1,5-di-tert-butyl (1c), and 2,5-di-tert-butyl (1d) derivatives underwent isomerization to phenylallenes 2, 3, 7, and 3, respectively. 2,5-Di-tert-butyl-7-vinylcyclohepta-1,3,5-triene (17) gave a mixture (66:34) of (E)- and (Z)-1,4-di-tert-butyl-2-(1-propenyl)benzene (20). A mechanism involving the protonation of the norcaradiene tautomer (NCD), which is in equilibrium with cycloheptatriene (CHT) 1 or 17, followed by the cleavage of a three-membered ring to give an arenium ion, is proposed. In contrast, 2,5-di-tert-butyl-7-cyanocyclohepta-1,3,5-triene (12) and bis(cyclohepta-2,4,6-trien-1-yl)ethyne (21) did not give the expected products, probably due to the unfavorable energetics of the ring-opening step. A thermal 1,5-hydrogen shift predominates in these cases. Kinetic studies indicated that the rearrangement of 1a is significantly accelerated by the presence of tert-butyl groups on the seven-membered ring. The order of reactivity, 1a 〈 1b 〈 1c 〈 1d, is in agreement with the population of NCD forms at equilibrium, as estimated by the calculated CHT-NCD energy-difference and the 13C NMR chemical shifts of 1a-d, indicating the importance of the equilibrium concentration of the norcaradiene form as a rate-controlling factor. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003.
Zinc promoted asymmetric propargylation of N-(2-chlorotetrafluoroethanesulfin)imines
Liu, Li-Juan,Liu, Jin-Tao
, p. 44 - 49 (2014)
Zinc promoted asymmetric Barbier-type homopropargylation of aldimines is demonstrated. 2-Chlorotetrafluoroethanesulfinamide was used as the chiral auxiliary and the corresponding homopropargylamines were obtained in good yields with up to 98% diastereosel
Nickel-catalyzed coupling of terminal allenes, aldehydes, and silanes
Ng, Sze-Sze,Jamison, Timothy F.
, p. 11350 - 11359 (2006)
The development of a nickel-catalyzed coupling of terminal allenes, aldehydes, and silanes is described. This transformation selectively provides 1,1-disubstituted allylic alcohols, protected as a silyl ether. The choice of the reducing agent is essential
Acid-catalyzed rearrangement of ethynylcycloheptatriene to phenylallene
Kitagawa, Toshikazu,Kamada, Jun,Minegishi, Shinya,Takeuchi, Ken'ichi
, p. 3011 - 3013 (2000)
7-Ethynylcycloheptatriene (1) cleanly isomerizes to phenylallene in the presence of acid A machanism involving the protonation of ethynylnorcaradiene, which is in equilibrium with 1, followed by the cleavage of a three-membered ring to give an arenium ion, is proposed. The rearrangement is accelerated by a factor of 370 by introducing tert-butyl groups on C-2 and C-5, indicating the importance of the equilibrium concentration of the norcaradiene form as a rate-controlling factor.
Photoredox Catalyzed Sulfonylation of Multisubstituted Allenes with Ru(bpy)3Cl2 or Rhodamine B
Chen, Jingyun,Chen, Shufang,Jiang, Jun,Lu, Qianqian,Shi, Liyang,Xu, Zekun,Yimei, Zhao
supporting information, (2021/11/09)
A highly regio- and stereoselective sulfonylation of allenes was developed that provided direct access to α, β-substituted unsaturated sulfone. By means of visible-light photoredox catalysis, the free radicals produced by p-toluenesulfonic acid reacted with multisubstituted allenes to obtain Markovnikov-type vinyl sulfones with Ru(bpy)3Cl2 or Rhodamine B as photocatalyst. The yield of this reaction could reach up to 91%. A series of unsaturated sulfones would be used for further transformation to some valuable compounds.
Polymerization of Allenes by Using an Iron(II) β-Diketiminate Pre-Catalyst to Generate High Mn Polymers
Durand, Derek J.,Webster, Ruth L.,Woof, Callum R.
supporting information, p. 12335 - 12340 (2021/07/19)
Herein, we report an iron(II)-catalyzed polymerization of arylallenes. This reaction proceeds rapidly at room temperature in the presence of a hydride co-catalyst to generate polymers of weight up to Mn=189 000 Da. We have determined the polymer structure and chain length for a range of monomers through a combination of NMR, differential scanning calorimetry (DSC) and gel permeation chromatography (GPC) analysis. Mechanistically, we postulate that the co-catalyst does not react to form an iron(II) hydride in situ, but instead the chain growth is proceeding via a reactive Fe(III) species. We have also performed kinetic and isotopic experiments to further our understanding. The formation of a highly unusual 1,3-substituted cyclobutane side-product is also investigated.
Enantioselective Addition of α-Nitroesters to Alkynes
Davison, Ryan T.,Parker, Patrick D.,Hou, Xintong,Chung, Crystal P.,Augustine, Sara A.,Dong, Vy M.
supporting information, p. 4599 - 4603 (2021/01/18)
By using Rh–H catalysis, we couple α-nitroesters and alkynes to prepare α-amino-acid precursors. This atom-economical strategy generates two contiguous stereocenters, with high enantio- and diastereocontrol. In this transformation, the alkyne undergoes isomerization to generate a RhIII–π-allyl electrophile, which is trapped by an α-nitroester nucleophile. A subsequent reduction with In powder transforms the allylic α-nitroesters to the corresponding α,α-disubstituted α-amino esters.
Copper(ii)-catalyzed protoboration of allenes in aqueous media and open air
Nekvinda, Jan,Santos, Webster L.,Snead, Russell F.
supporting information, p. 14925 - 14931 (2021/09/04)
A method has been developed for the facile Cu(ii)-catalyzed protoboration of monosubstituted allenes in aqueous media under atmospheric conditions. The reaction occurs site selectively, favoring internal alkene protoboration to afford 1,1-disubstituted vinylboronic acid derivatives (up to 93?:?7) with modest to good yields. The method has been applied to a variety of phenylallene derivatives as well as alkyl-substituted allenes. This journal is
Photoredox-Catalyzed α-Aminoalkylcarboxylation of Allenes with CO2
Hahm, Hyungwoo,Baek, Doohyun,Kim, Dowon,Park, Seongwook,Ryoo, Jeong Yup,Hong, Sukwon
supporting information, p. 3879 - 3884 (2021/05/29)
The photoredox-catalyzed α-aminoalkylcarboxylation of aryl allenes with CO2 and N,N-dimethylanilines is reported for the first time (26 examples, up to 96% yield). In the case of electron-deficient allenes, good regioselectivity was observed (up to 94:6), exclusively generating kinetic products over thermodynamic products. This protocol is a novel synthetic method for highly functionalized β,γ-unsaturated γ-aminobutyric esters.
