118970-95-9Relevant articles and documents
London Dispersion Interactions Rather than Steric Hindrance Determine the Enantioselectivity of the Corey–Bakshi–Shibata Reduction
Eschmann, Christian,Song, Lijuan,Schreiner, Peter R.
supporting information, p. 4823 - 4832 (2021/02/01)
The well-known Corey–Bakshi–Shibata (CBS) reduction is a powerful method for the asymmetric synthesis of alcohols from prochiral ketones, often featuring high yields and excellent selectivities. While steric repulsion has been regarded as the key director of the observed high enantioselectivity for many years, we show that London dispersion (LD) interactions are at least as important for enantiodiscrimination. We exemplify this through a combination of detailed computational and experimental studies for a series of modified CBS catalysts equipped with dispersion energy donors (DEDs) in the catalysts and the substrates. Our results demonstrate that attractive LD interactions between the catalyst and the substrate, rather than steric repulsion, determine the selectivity. As a key outcome of our study, we were able to improve the catalyst design for some challenging CBS reductions.
Stereoselective Total Synthesis of (-)-(2 S,4 R)-3′-Methoxyl Citreochlorol: Preparation and Use of New Proline-Based Auxiliary for Asymmetric Acetate Aldol Reaction
Sunnapu, Ranganayakulu,Banoth, Saikumar Naik,Reyno,Thomas, Aleena,Venugopal, Navyasree,Rajendar, Goreti
, p. 4103 - 4113 (2020/03/05)
The first stereoselective total synthesis of (-)-(2S,4R)-3′-methoxy citreochlorol and (-)-(2S,4S)-3′-methoxy citreochlorol is demonstrated. A proline-based imidazolidinone was synthesized and used as chiral auxiliary for asymmetric acetate aldol reaction to generate initial chirality in the targeted molecule. Geminal dichloromethane functionality was introduced by the addition of in situ generated dichloromethyllithium to Weinreb's amide functional group.
Intramolecular [2+2] Photocycloaddition of Cyclic Enones: Selectivity Control by Lewis Acids and Mechanistic Implications
Poplata, Saner,Bauer, Andreas,Storch, Golo,Bach, Thorsten
supporting information, p. 8135 - 8148 (2019/05/29)
The intramolecular [2+2] photocycloaddition of 3-alkenyl-2-cycloalkenones was performed in an enantioselective fashion (nine representative examples, 54–86 % yield, 76–96 % ee) upon irradiation at λ=366 nm in the presence of an AlBr3-activated oxazaborolidine as the Lewis acid. An extensive screening of proline-derived oxazaborolidines showed that the enantioface differentiation depends strongly on the nature of the aryl group at the 3-position of the heterocycle. DFT calculations of the Lewis acid–substrate complex indicate that attractive dispersion forces may be responsible for a change of the binding mode. The catalytic [2+2] photocycloaddition was shown to proceed on the triplet hypersurface with a quantum yield of 0.05. The positive effect of Lewis acids on the outcome of a given intramolecular [2+2] photocycloaddition was illustrated by optimizing the key step in a concise total synthesis of the sesquiterpene (±)-italicene.
Transition Metal-Free Selective Double sp3 C-H Oxidation of Cyclic Amines to 3-Alkoxyamine Lactams
Osorio-Nieto, Urbano,Chamorro-Arenas, Delfino,Quintero, Leticia,H?pfl, Herbert,Sartillo-Piscil, Fernando
, p. 8625 - 8632 (2016/09/28)
The first chemical method for selective dual sp3 C-H functionalization at the alpha-and beta positions of cyclic amines to their corresponding 3-alkoxyamine lactams is reported. Unlike traditional Cα-H oxidation of amines to amides mediated by transition metals, the present protocol, which involves the use of NaClO2/TEMPO/NaClO in either aqueous or organic solvent, not only allows the Cα-H oxidation but also the subsequent functionalization of the unreactive β-methylene group in an unprecedented tandem fashion and using environmentally friendly reactants.
Concise synthesis of chiral N -Benzyl-α,α-Diarylprolinols through shi asymmetric epoxidation
Li, Jie,Zhou, Hai,Weng, Jiangsen,Wang, Mingwen,Ge, Chengsheng,Tu, Wujie
supporting information, p. 805 - 808 (2014/04/03)
A concise and practical synthesis of chiral N-benzyl-α,α- diaryl-2-prolinols was developed through Shi asymmetric epoxidation, followed by double nucleophilic substitution of bromo-containing olefins. A series of enantioenriched N-benzyl-α,α-diaryl-2-prolinols were obtained with excellent enantioselectivities (96% ee) in moderate to good yields (40-76% yield). For the first time, enantiopure N-benzyl-α,α-diphenyl-2- prolinol was obtained from bromo-containing olefin using this methodology. Georg Thieme Verlag Stuttgart, New York.
Synthesis of chiral 2-(anilinophenylmethyl)pyrrolidines and 2-(anilinodiphenylmethyl)pyrrolidine and their application to enantioselective borane reduction of prochiral ketones as chiral catalysts
Hosoda, Naoya,Kamito, Hideaki,Takano, Miki,Takebe, Yoshitaka,Yamaguchi, Yoshitaka,Asami, Masatoshi
, p. 1739 - 1746 (2013/03/13)
Chiral diamines, 2-(anilinophenylmethyl)pyrrolidines and 2-(anilinodiphenylmethyl)pyrrolidine, were prepared from N-(tert-butoxycarbonyl) pyrrolidine or (S)-proline as a starting material, respectively. These chiral diamines were efficient for the catalytic enantioselective borane reduction of acetophenone. Using (S)-2-(anilinodiphenylmethyl)pyrrolidine, chiral secondary alcohols were obtained from prochiral ketones with good to excellent enantiomeric excesses (up to 98% ee).
Catalytic asymmetric aldol-type reaction of zinc enolate equivalent of amides
Haraguchi, Ryosuke,Matsubara, Seijiro
supporting information, p. 3378 - 3380 (2013/07/26)
Treatment of phenyl isocyanate with bis(iodozincio)methane gave a zinciomethylenated product, which acts as an amide-enoate equivalent. It did not react with an aldehyde efficiently, but gave the corresponding adduct in good yield in the presence of an aminoalcohol. Use of a catalytic amount of chiral aminoalcohol led the process to the catalytic asymmetric Aldol-type reaction.
Allyltin tribromide: A versatile reagent involved in the ring-opening of epoxides
Chen, Guohong,Wang, Xin,Jin, Xiaoqian,Liu, Lingyan,Chang, Weixing,Li, Jing
experimental part, p. 1294 - 1301 (2010/11/05)
This paper presents a versatile reagent for epoxide cleavage. The allyltin tribromide could act as a novel and easily prepared allylation reagent and halide atom donor to convert epoxides to the corresponding homoallyl alcohols and halohydrins in high yields with excellent regioselectivities under mild reaction conditions, respectively. It could also act as a Lewis acid to catalyze the ring opening reactions of epoxides with alcohols.
A concise synthesis of (S)-2-(fluorodiphenylmethyl)pyrrolidine: A novel organocatalyst for the stereoselective epoxidation of α,β-unsaturated aldehydes
Sparr, Christof,Tanzer, Eva-Maria,Bachmann, Julia,Gilmour, Ryan
experimental part, p. 1394 - 1397 (2010/07/02)
A concise synthesis of (S)-2-(fluorodiphenylmethyl)pyrrolidine from cheap, commercially available starting materials is described. Pertinent features of this synthetic route include ease of synthesis, facile purification steps, and an operationally simple deoxy?fluorination step to install the C-F bond. Georg Thieme Verlag Stuttgart · New York.
