Catalytic Asymmetric Cyclopropanation of Allylic Alcohols with Titanium-TADDOLate: Scope of the Cyclopropanation Reaction
作者:André B. Charette、Carmela Molinaro、Christian Brochu
DOI:10.1021/ja0108382
日期:2001.12.1
titanium-TADDOLate complex was effective at catalyzing the cyclopropanation reaction of allylicalcohols in the presence 1 equiv of bis(iodomethyl)zinc. After initial optimization of the catalyst structure, excellent yields and enantiomeric ratios were obtained for 3-aryl- or 3-heteroaryl-substituted allylicalcohols (up to 97:3). Alkyl-substituted allylicalcohols gave modest yields and enantiomeric ratios (up
Highly Enantioselective Intermolecular Cyclopropanation Catalyzed by Dirhodium(II) Tetrakis[3(<i>S</i>)-phthalimido-2-piperidinonate]: Solvent Dependency of the Enantioselection
The enantioselectivity in cyclopropanations catalyzed by dirhodium(II) tetrakis[3(S)-phthalimido-2-piperidinonate] has been found to be substantially improved by employing ether as the rarely used solvent. Cyclopropanations of styrenes or 1,1-disubstituted alkenes with 2,4-dimethyl-3-pentyl diazoacetate in ether are promoted by this catalyst to afford the corresponding cyclopropane products in the highest levels of enantioselectivity (up to 98% ee) reported to date for the dirhodium(II)-catalyzed intermolecular cyclopropanation reactions.
ee) was prepared by cyclopropanation of 3,3-diphenyl-2-propen-1-ol 1 with Et2Zn and CH2I2 in the presence of a catalytic amount of (S)-2-(methanesulfonyl)amino-1-(p-toluenesulfonyl)amino-3-phenylpropane 2, followed by esterification with 3,5-dinitorobenzoyl chloride, recrystallization, and hydrolysis.
由(+)-2,2-二苯基环丙基甲醇3a(98%ee)分两步合成(R)-(+)-噻吩啉(95%ee ),将其在DMSO中用IBX氧化,然后在乙二胺中用乙二胺处理。存在的我2和K 2 CO 3在吨BuOH中。化合物(R)-(+)- 3a(98%ee)通过在催化量存在下,将3,3-二苯基-2-丙烯-1-醇1与Et 2 Zn和CH 2 I 2环丙烷化制备的(小号)-2-(甲磺酰基)氨基-1-(p甲苯磺酰)氨基-3-苯基丙烷2,然后用3,5-二硝基苯甲酰氯进行酯化,重结晶和水解。
Catalytic, Enantioselective Cyclopropanation of Allylic Alcohols. Substrate Generality
作者:Scott E. Denmark、Stephen P. O'Connor
DOI:10.1021/jo961859v
日期:1997.2.1
critical for the rapid and selective cyclopropanation: (1) use of the ethylzinc alkoxide of the allylic alcohol as the substrate by prior deprotonation of the allylic alcohols by diethylzinc, (2) the formation of the zinc complex of the promoter by prior deprotonation of the bis-sulfonamide with diethylzinc, and (3) the use of added zinc iodide generated in situ from diethylzinc and iodine. The stereoselectivity
Donor‐Acceptor Cyclopropanes: Activation Enabled by a Single, Vinylogous Acceptor
作者:Nils L. Ahlburg、Oliver Hergert、Peter G. Jones、Daniel B. Werz
DOI:10.1002/anie.202214390
日期:2023.1.2
A new class of donor-acceptor cyclopropanes bearing only a single, vinylogousacceptor moiety is presented. The system is capable of cycloadditions through Brønsted or Lewis acid catalysis with numerous reagents: aldehydes, ketones, thioketones, nitriles, naphth-2-ols, cyclopropanes, nitrones and isobenzofurans. The mechanism was explored in detail by kinetic and mechanistic experiments.