144412-92-0Relevant academic research and scientific papers
Palladium-Catalyzed Asymmetric Tandem Denitrogenative Heck/Tsuji-Trost of Benzotriazoles with 1,3-Dienes
Li, Yin-Lin,Wu, Hai-Hong,Zhang, Junliang,Zhang, Pei-Chao
supporting information, p. 13010 - 13015 (2021/09/07)
The asymmetric denitrogenative cycloaddition has emerged as a powerful tool to build chiral aza-heterocyles. However, only one example of asymmetric denitrogenative cycloaddition of benzotriazole with unsaturated hydrocarbons has been explored so far, bec
Preparation of optically active cycloalkenes bearing all-carbon quaternary stereogenic centres: Via lipase-oxovanadium combo-catalysed dynamic kinetic resolution
Kawanishi, Shinji,Sugiyama, Koji,Oki, Yasuhiro,Ikawa, Takashi,Akai, Shuji
, p. 411 - 417 (2017/08/14)
In this study, a novel asymmetric synthesis of all-carbon quaternary stereogenic centres is developed by the connection of three prochiral or achiral components - conjugated enones, organometallic compounds and vinyl esters - at the C-1 position of the enones. This method involves three sequential steps: 1,2-nucleophilic addition of an organometallic compound to the enone, lipase-catalysed dynamic kinetic resolution (DKR) of the tert-allylic alcohol and the Ireland-Claisen rearrangement of the optically active allyl ester thus generated. This method features the effective use of acyl moieties installed by DKR for achieving high atom economy. The application of this method to the protective-group-free asymmetric total synthesis of (-)-crinane, a core structure of a class of natural alkaloids, has demonstrated that it can alter a known synthetic pathway of a racemate into an asymmetric synthesis of an optically pure molecule while reducing the total transformation steps and increasing the overall yield. With these advantages, this method is practical and attractive as a new environmentally benign protocol.
Cu-catalyzed enantioselective 1,4-additions of aryl-Grignard reagents to cyclohexenone in the presence of TADDOL-derived phosphane-phosphite ligands
Naeemi, Qaseem,Dindaroglu, Mehmet,Kranz, Darius P.,Velder, Janna,Schmalz, Hans-Guenther
experimental part, p. 1179 - 1185 (2012/04/10)
Asymmetric conjugate additions (1,4-additions) of aryl-Grignard reagents to cyclohex-2-enone, currently a more or less unsolved challenge, were investigated. For this purpose, a small library of phenol-derived chiral phosphane-phosphite ligands containing TADDOL- or BINOL-based phosphite moieties was evaluated. These ligands are easily prepared by a short modular scheme previously developed in this laboratory. Two particularly powerful ligands (4a and 4b, both TADDOL-derived and each possessing a bulky tert-butyl substituent ortho to the phosphite group) were identified. Conditions were optimized with use of the addition of (4-methoxyphenyl)magnesium bromide to cyclohexenone as a standard reaction system. Under optimized conditions [CuBr·SMe 2 (4 mol-%), ligand 4a (6 mol-%), 2-methyl-THF, -78 °C, slow addition of Grignard reagent] the 1,4-product was obtained with high enantioselectivity (up to 95 % ee) and good regioselectivity (r.r. = 90:10). The scope of the method was probed with different aryl-Grignard reagents. It was found that reagents with electron-donating substituents in meta- or para-positions performed particularly well, whereas the presence of F or CF 3 substituents led to decreased ee values. Only ortho-substituted aryl-Grignard reagents did not give rise to useful results. A series of phosphane-phosphite ligands were also tested in the Rh-catalyzed 1,4-addition of phenylboronic acid to cyclohexenone, but enantioselectivities did not exceed 70 % ee in this case. The difficult task of employing aryl-Grignard reagents in Cu-catalyzed enantioselective 1,4 addition reactions was achieved with the assistance of readily accessible chiral modular P,P ligands. High enantioselectivities were obtained in a number of synthetically relevant cases. Copyright
An efficient synthesis of (±)-crinane using an intramolecular azide-olefin cycloaddition
Schkeryantz, Jeffrey M.,Pearson, William H.
, p. 3107 - 3116 (2007/10/03)
Refluxing 3-(2-azidoethyl)-3-[3,4-(methylenedioxy)phenyl]cyclohex-1-ene (2) in toluene for 24 hours afforded 3a-[3,4-methylenedioxy)phenyl]-3,3a,4,5,6,7-hexahydro-2H-indole (12) in quantitative yield. This reaction proceeds by intramolecular 1,3-dipolar cycloaddition of the azide onto the alkene followed by loss of nitrogen from the triazoline intermediate to give an imine. Reduction of the imine 12 with sodium cyanoborohydride in acetic acid/THF gave (3aR*, 7aR*)-3a-[3,4-methylenedioxy)phenyl]-2,3,3a,4,5,6,7,7a-octahydroindol e (13). Warming 13 with Eschenmoser's salt provided (±)-crinane (1). The synthesis of (±)-crinane (1) from cyclohexenone was accomplished in 8 steps in 23% overall yield.
