Studies of the regiospecific 3-aza-Cope rearrangement promoted by electrophilic reagents
摘要:
The 3-aza-Cope rearrangement of N-alkyl-N-allyl enamine substrates, which required temperatures of 250 250-degrees-C to proceed thermally, was promoted at 111-degrees-C in the presence of electrophilic reagents such as HCl (0.5 equiv) TiCl4 (0.2 equiv), AlMe3 (1.2 equiv), or (ArO)2AlMe (1.2 equiv). In order to probe the regioselectivity of this accelerated carbon-carbon bond forming process under these reaction conditions, several enamine substrates were prepared from both isobutyraldehyde and cyclohexanone. Each substrate used in these studies was prepared having an unsymmetrical N-allylic group, substituted with either an alkyl or phenyl substituent at the 4 or 6 position of the 3-aza-Cope framework. In all cam examined, reaction acceleration by the electrophilic reagent produced regiospecific [3,3] rearrangement to the corresponding products resulting from [1,3] rearrangement were not observed. Hydride reduction of the resulting imines generated the delta,epsilon-unsaturated amines in 55-94% overall yield in the three-step condensation-rearrangement-reduction process from the secondary allylamine.
Enzymatic Primary Amination of Benzylic and Allylic C(sp<sup>3</sup>)–H Bonds
作者:Zhi-Jun Jia、Shilong Gao、Frances H. Arnold
DOI:10.1021/jacs.0c03428
日期:2020.6.10
processes are reported for their synthesis, methods that directly install a primary amine group into C(sp3)-H bonds remain unprecedented. Here, we report a set of new-to-nature enzymes that catalyzes the direct primary amination of C(sp3)-H bonds with excellent chemo-, regio-, and enantioselectivity, using a readily available hydroxylamine derivative as the nitrogen source. Directed evolution of genetically-encoded
mL of toluene, Rh(acac)(CO)2 as the metal precursor, (S,R)-(N-Bn)Yanphos as the ligand, CO:H2 = 10:10 bar, S/C = 20, HSiEt3 (0.3 mmol), and BF3.Et2O (0.3 mmol) The configuration of all of the products was determined to be S, except for 4m; only the desired regioisomer was obtained as determined by NMR analysis. Scheme 4. Synthetic Transformations Addition/Correction
反应以 0.1 mmol 规模在 0.5 mL 甲苯中进行,Rh(acac)(CO)2 作为金属前体,(S,R)-(N-Bn)Yanphos 作为配体,CO:H2 = 10: 10 bar, S/C = 20, HSiEt3 (0.3 mmol), and BF3.Et2O (0.3 mmol) 通过NMR分析确定仅获得所需的区域异构体。方案 4. 合成变换加法/校正
Rhodium/Yanphos-Catalyzed Asymmetric Interrupted Intramolecular Hydroaminomethylation of <i>trans</i>-1,2-Disubstituted Alkenes
The first interruptedasymmetrichydroaminomethylation reaction was developed. The challenging trans-1,2-disubstituted olefins were employed as substrates, and a series of valuable chiral pyrrolidinones and pyrrolidines were obtained in high yields with high regioselectivities and excellent enantioselectivities. Several synthetic transformations were conducted, demonstrating the high synthetic utility
Rh(III)-Catalyzed C–H Activation-Initiated Directed Cyclopropanation of Allylic Alcohols
作者:Erik J. T. Phipps、Tomislav Rovis
DOI:10.1021/jacs.9b02156
日期:2019.5.1
annulation onto allylic alcohols initiated by alkenyl C-H activation of N-enoxyphthalimides to furnish substituted cyclopropyl-ketones. Notably, the traceless oxyphthalimide handle serves three functions: directing C-H activation, oxidation of Rh(III), and, collectively with the allylic alcohol, in directing cyclopropanation to control diastereoselectivity. Allylic alcohols are shown to be highly reactive
Retro-Cope eliminations in the synthesis of 1,2,5-oxadiazinanes from allylamines and nitrones: a method for the amination of unactivated alkenes
作者:Michael B. Gravestock、David W. Knight、Steven R. Thornton
DOI:10.1039/c39930000169
日期:——
Heating an allylamine (e.g.9) and a nitrone (e.g.10) in an inert solvent produces often excellent yields of a 1,2,5-oxadiazinane (e.g.11) by a pathway which features a retro-Cope elimination and a Meisenheimer rearrangement; reduction of the oxadiazinanes leads to vicinal diamines and hence overall amination of the alkene function in the original allylamine.