131154-18-2Relevant academic research and scientific papers
Enantioselective Tail-to-Head Cyclizations Catalyzed by Dual-Hydrogen-Bond Donors
Kutateladze, Dennis A.,Strassfeld, Daniel A.,Jacobsen, Eric N.
, p. 6951 - 6956 (2020/05/19)
Chiral urea derivatives are shown to catalyze enantioselective tail-to-head cyclization reactions of neryl chloride analogues. Experimental data are consistent with a mechanism in which ?-participation by the nucleophilic olefin facilitates chloride ionization and thereby circumvents simple elimination pathways. Kinetic and computational studies support a cooperative mode of catalysis wherein two molecules of the urea catalyst engage the substrate and induce enantioselectivity through selective transition state stabilization.
Highly Enantioselective, Hydrogen-Bond-Donor Catalyzed Additions to Oxetanes
Strassfeld, Daniel A.,Wickens, Zachary K.,Picazo, Elias,Jacobsen, Eric N.
supporting information, p. 9175 - 9180 (2020/07/13)
A precisely designed chiral squaramide derivative is shown to promote the highly enantioselective addition of trimethylsilyl bromide (TMSBr) to a broad variety of 3-substituted and 3,3-disubstituted oxetanes. The reaction provides direct and general access to synthetically valuable 1,3-bromohydrin building blocks from easily accessed achiral precursors. The products are readily elaborated both by nucleophilic substitution and through transition-metal-catalyzed cross-coupling reactions. The enantioselective catalytic oxetane ring opening was employed as part of a three-step, gram-scale synthesis of pretomanid, a recently approved medication for the treatment of multidrug-resistant tuberculosis. Heavy-atom kinetic isotope effect (KIE) studies are consistent with enantiodetermining delivery of bromide from the H-bond-donor (HBD) catalyst to the activated oxetane. While the nucleophilicity of the bromide ion is expected to be attenuated by association to the HBD, overall rate acceleration is achieved by enhancement of Lewis acidity of the TMSBr reagent through anion abstraction.
Development of Chemo- and Enantioselective Palladium-Catalyzed Decarboxylative Asymmetric Allylic Alkylation of α-Nitroesters
Trost, Barry M.,Schultz, Johnathan E.,Bai, Yu
supporting information, p. 11820 - 11825 (2019/07/31)
We describe the development of a Pd-catalyzed decarboxylative asymmetric allylic alkylation of α-nitro allyl esters to afford acyclic tetrasubstituted nitroalkanes. Optimization of the reaction parameters revealed unique ligand and solvent combinations crucial for achieving chemo- and enantioselective C-alkylation of electronically challenging benzylic nitronates and sterically encumbered 2-allyl esters. Substrates were efficiently accessed in a combinatorial fashion by a cross-Claisen/ α-arylation sequence. The method provides functional group orthogonality that complements nucleophilic imine allylation strategies for α-tertiary amine synthesis.
Copper-catalyzed asymmetric allylation of chiral N-tert-butanesulfinyl imines: Dual stereocontrol with nearly perfect diastereoselectivity
Zhao, Yi-Shuang,Liu, Qiang,Tian, Ping,Tao, Jing-Chao,Lin, Guo-Qiang
supporting information, p. 4174 - 4178 (2015/04/14)
Copper-catalyzed asymmetric allylation of chiral N-tert-butanesulfinyl imines has been described. Dual stereocontrol, through the combination of a chiral auxiliary and a chiral copper complex, has played an important role in achieving the nearly perfect d
Nonracemic 3°-carbamines from the asymmetric allylboration of N-trimethylsilyl ketimines with B-allyl-10-phenyl-9-borabicyclo[3.3.2]decanes
Canales, Eda,Hernandez, Eliud,Soderquist, John A.
, p. 8712 - 8713 (2007/10/03)
The simple and efficient asymmetric synthesis of 3°-carbamines 7 from N-TMS enamines (3) and either enantiomeric form of β-allyl-10-(phenyl)-9-borabicyclo[3.3.2]decane (1) is reported. The high reactivity (1 h, -78 °C) and enantioselectivity (60-98% ee) of these substrates can be attributed to the fact that the complexation of 3 with 1 facilitates its isomerization to the corresponding syn-N-TMS ketimine complex from which allylation can occur. In addition to providing the homoallylic amines 7 with predictable stereochemistry, the procedure also permits the efficient recovery of the chiral boron moiety (50-65%) as air-stable crystalline pseudoephedrine complexes 8, which are directly converted back to 1 with allylmagnesium bromide in ether (98%). Copyright
Room-temperature highly diastereoselective Zn-mediated allylation of chiral N-tert-butanesulfinyl imines: Remarkable reaction condition controlled stereoselectivity reversal
Sun, Xing-Wen,Xu, Ming-Hua,Lin, Guo-Qiang
, p. 4979 - 4982 (2007/10/03)
(Chemical Equation Presented) An efficient method for the highly diastereoselective synthesis of chiral homoallylic amines by Zn-mediated allylation of chiral N-tert-butanesulfinyl imines at room temperature was developed. By simply tuning the reaction co
Catalytic enantioselective allylation of ketoimines
Wada, Reiko,Shibuguchi, Tomoyuki,Makino, Sae,Oisaki, Kounosuke,Kanai, Motomu,Shibasaki, Masakatsu
, p. 7687 - 7691 (2007/10/03)
A general catalytic allylation of simple ketoimines was developed using 1 mol % of CuF·3PPh3 as catalyst, 1.5 mol % of La(O iPr)3 as the cocatalyst, and stable and nontoxic allylboronic acid pinacol ester as the nucleophile. This reaction constituted a good template for developing the first catalytic enantioselective allylation of ketoimines. In this case, using LiOiPr as the cocatalyst produced higher enantioselectivity and reactivity than La(OiPr)3. Thus, using the CuF-cyclopentyl-DuPHOS complex (10 mol %) and LiOiPr (30 mol %) in the presence of BuOH (1 equiv) produced high enantioselectivity up to 93% ee from a range of aromatic ketoimines. Mechanistic studies indicated that LiO iPr accelerates the reaction by increasing the concentration of an active nucleophile, allylcopper.
Enantioselective Allylation of Ketone-Derived Benzoylhydrazones: Practical Synthesis of Tertiary Carbinamines
Berger, Richard,Duff, Keiko,Leighton, James L.
, p. 5686 - 5687 (2007/10/03)
A highly practical method for the enantioselective allylation of ketone-derived benzoylhydrazones has been developed. The previously reported strained silacycle reagent 1 reacts with a wide variety of benzoylhydrazones to give the hydrazide products with
Stereoselective Addition Reactions of Chiral N-Benzylidene-p-toluenesulfinamides. Asymmetric Syntheses of β- and γ-Amino Acids
Hua, Duy H.,Miao, Shou Wu,Chen, Jin Shan,Iguchi, Sadahiko
, p. 4 - 6 (2007/10/02)
Chiral N-benzylidene-p-toluenesulfinamides 2 were prepared by the reaction of benzonitril with alkyllithium in ether followed by (-)-l-menthyl (S)-p-tolylsulfinate.Treatment of 2 with allylmagnesium bromide in ether at 0 deg C gave the adducts (R)-7 with excellent stereoselectivity.Pure chiral sulfinamides 7 were converted into β- and γ-amino acids in four and five steps, respectively.
