170899-02-2Relevant academic research and scientific papers
Application of Trimethylgermanyl-Substituted Bisphosphine Ligands with Enhanced Dispersion Interactions to Copper-Catalyzed Hydroboration of Disubstituted Alkenes
Xi, Yumeng,Su, Bo,Qi, Xiaotian,Pedram, Shayun,Liu, Peng,Hartwig, John F.
supporting information, p. 18213 - 18222 (2020/12/04)
We report the incorporation of large substituents based on heavy main-group elements that are atypical in ligand architectures to enhance dispersion interactions and, thereby, enhance enantioselectivity. Specifically, we prepared the chiral biaryl bisphosphine ligand (TMG-SYNPHOS) containing 3,5-bis(trimethylgermanyl)phenyl groups on phosphorus and applied this ligand to the challenging problem of enantioselective hydrofunctionalization reactions of 1,1-disubtituted alkenes. Indeed, TMG-SYNPHOS forms a copper complex that catalyzes hydroboration of 1,1-disubtituted alkenes with high levels of enantioselectivity, even when the two substituents are both primary alkyl groups. In addition, copper catalysts bearing ligands possessing germanyl groups were much more active for hydroboration than one derived from DTBM-SEGPHOS, a ligand containing 3,5-di-tert-butyl groups and widely used for copper-catalyzed hydrofunctionalization. This observation led to the identification of DTMGM-SEGPHOS, a bisphosphine ligand bearing 3,5-bis(trimethylgermanyl)-4-methoxyphenyl groups as the substituents on the phosphorus, as a new ligand that forms a highly active catalyst for hydroboration of unactivated 1,2-disubstituted alkenes, a class of substrates that has not readily undergone copper-catalyzed hydroboration previously. Computational studies revealed that the enantioselectivity and catalytic efficiency of the germanyl-substituted ligands is higher than that of the silyl and tert-butyl-substituted analogues because of attractive dispersion interactions between the bulky trimethylgermanyl groups on the ancillary ligand and the alkene substrate and that Pauli repulsive interactions tended to decrease enantioselectivity.
Synthesis and olfactory evaluation of optically active β-alkyl substituted γ-lactones and whiskey lactone analogues
Kato, Daiki,Kawasaki, Masashi,Morita, Yuko,Okada, Takuya,Tanaka, Yasuo,Toyooka, Naoki
supporting information, (2020/02/22)
Optically active β-alkyl substituted γ-lactones and whiskey lactone analogues were synthesized, and the odor properties were evaluated. During the preparation of the chiral intermediates, we found good reaction conditions for the highly enantioselective esterification of 3-arylmethyl-2-methyl-1-propanols to kinetically resolve them. The results of the olfactory evaluations of the synthesized lactones revealed that the alkyl groups on the γ-lactone rings played an important role for the odor profiles.
Controllable, Sequential, and Stereoselective C-H Allylic Alkylation of Alkenes
Qin, Ling,Sharique, Mohammed,Tambar, Uttam K.
, p. 17305 - 17313 (2019/11/03)
The direct conversion of C-H bonds into new C-C bonds represents a powerful approach to generate complex molecules from simple starting materials. However, a general and controllable method for the sequential conversion of a methyl group into a fully substituted carbon center remains a challenge. We report a new method for the selective and sequential replacement of three C-H bonds at the allylic position of propylene and other simple terminal alkenes with different carbon groups derived from Grignard reagents. A copper catalyst and electron-rich biaryl phosphine ligand facilitate the formation of allylic alkylation products in high branch selectivity. We also present conditions for the generation of enantioenriched allylic alkylation products in the presence of catalytic copper and a chiral phosphine ligand. With this approach, diverse and complex products with substituted carbon centers can be generated from simple and abundant feedstock chemicals.
Enantioselective Formal α-Methylation and α-Benzylation of Aldehydes by Means of Photo-organocatalysis
Filippini, Giacomo,Silvi, Mattia,Melchiorre, Paolo
supporting information, p. 4447 - 4451 (2017/04/13)
Detailed herein is the photochemical organocatalytic enantioselective α-alkylation of aldehydes with (phenylsulfonyl)alkyl iodides. The chemistry relies on the direct photoexcitation of enamines to trigger the formation of reactive carbon-centered radicals from iodosulfones, while the ground-state chiral enamines provide effective stereochemical control over the radical trapping process. The phenylsulfonyl moiety, acting as a redox auxiliary group, facilitates the generation of radicals. In addition, it can eventually be removed under mild reducing conditions to reveal methyl and benzyl groups.
Catalytic enantioselective ethylalumination of terminal alkenes: Substrate effects and absolute configuration assignment
Parfenova, Lyudmila V.,Kovyazin, Pavel V.,Tyumkina, Tatyana V.,Makrushina, Alyona V.,Khalilov, Leonard M.,Dzhemilev, Usein M.
, p. 124 - 135 (2015/02/19)
The chemo- and enantioselectivity of the reaction of alkenes with AlEt3 catalyzed by bis(1-neomenthylindenyl)zirconium dichloride has been studied. The reaction with linear alkenes in a chlorinated solvent (CH2Cl2) gives m
Highly enantioselective conjugate additions of aldehydes to vinyl sulfones
Landa, Aitor,Maestro, Miguel,Masdeu, Carme,Puente, Angel,Vera, Silvia,Oiarbide, Mikel,Palomo, Claudio
supporting information; experimental part, p. 1562 - 1565 (2009/10/01)
The use of less basic chiral amine catalysts for highly enantioselective conjugate additions of aldehydes to vinyl sulfones was reported. The results show that the addition of aldehydes to α-cyano vinyl sulfones takes place at -40°C to give alcohols. The
Organocatalytic Michael addition of aldehydes to vinyl sulfones: Enantioselective α-alkylations of aldehydes and their derivatives
Zhu, Qiang,Lu, Yixin
supporting information; experimental part, p. 4803 - 4806 (2009/05/31)
(Equation Presented) Organocatalytic asymmetric Michael reaction of unmodified aldehydes to vinyl sulfones catalyzed by silylated biarylprolinol afforded the desired Michael products with exceptional enantioselectivity. The described enantioselective addition to vinyl sulfones, in combination with desulfonation, offers a unique, asymmetric entry to α-alkylated aldehydes and their derivatives.
SuperQuat N-acyl-5,5-dimethyloxazolidin-2-ones for the asymmetric synthesis of α-alkyl and β-alkyl aldehydes
Bull, Steven D.,Davies, Stephen G.,Nicholson, Rebecca L.,Sanganee, Hitesh J.,Smith, Andrew D.
, p. 2886 - 2899 (2007/10/03)
The proclivity of α-branched N-2′-benzyl-3′-phenylpropionyl derivatives of (S)-4-benzyl-5,5-dimethyl-, (S)-4-phenyl-5,5-dimethyl-, (S)-4-isopropyl-5,5-dimethyl-, (S)-4-benzyl- and (S)-4-benzyl-5,5-diphenyl-oxazolidin-2-ones to generate directly 2-benzyl-3-phenylpropionaldehyde upon hydride reduction with DIBAL is investigated. The (S)-4-benzyl-5,5-dimethyl-derivative proved optimal for inhibition of endocyclic nucleophilic attack, giving 2-benzyl-3-phenylpropionaldehyde in good yield upon reduction. Application of this methodology for the asymmetric synthesis of chiral aldehydes via diastereoselective enolate alkylation of a range of (S)-N-acyl-4-benzyl-5,5-dimethyloxazolidin-2-ones to afford an array of α-substituted-N-acyl-5,5-dimethyloxazolidin-2-ones (85-94% de) and subsequent reduction with DIBAL afforded directly non-racemic α-substituted aldehydes without loss of stereochemical integrity (87-94% ee). The extension of this protocol for the asymmetric synthesis of β-substituted aldehydes is demonstrated, via the diastereoselective conjugate addition of a range of organocuprates to (S)-N-acyl-4-phenyl-5,5-dimethyloxazolidin-2-ones which proceeds with high diastereoselectivity (generally >95% de). Reduction of the conjugate addition products with DIBAL gives non-racemic β-substituted aldehydes in high yields and in high ee (generally >95% ee). This methodology is exemplified by the asymmetric synthesis of (R)-3-isopropenylhept-6-enal, which has previously been used in the synthesis of (3Z,6R)-3-methyl-6-isopropenyl-3,9-decadien-1-yl acetate, a component of the sex pheromones of the California red scale.
Kumada - Corriu coupling of Grignard reagents, probed with a chiral Grignard reagent
Hoelzer, Bettina,Hoffmann, Reinhard W.
, p. 732 - 733 (2007/10/03)
The Grignard reagent 2, in which the magnesium-bearing carbon atom is the sole stereogenic centre has been coupled with vinyl bromide under Pd(0) or Ni(0)-catalysis to give compound 3 with full retention of configuration. Coupling using Fe(acac)3/su
An easy access to enantio-enriched α-substituted aldehydes by carbolithiation of β-phenyl or β-silyl-α,β-ethylenic aldehydes, protected with the monolithioamide of a chiral diamine
Brémand, Nathalie,Mangeney, Pierre,Normant, Jean F.
, p. 1883 - 1885 (2007/10/03)
Lithium amide derived from N,N,N′-trimethyl-1,2-diphenylethanediamine converts cinnamaldehyde to a lithium alkoxyamide which undergoes a regio- and stereoselective carbolithiation upon addition of various organolithiums. Subsequent hydrolysis or trapping with MeI delivers α-mono-, or α,β-disubstituted 3-phenylpropanals with e.e.s of 76-96%. Extension to a silylated α-enal is possible.
