Regulation of Diastereoselectivity in the Carbocyclization of Allenyl (S)-N-tert-Butylsulfinimines through a Three-Component Assembly
摘要:
Allenyl sulfinimines can be stereoselectively cyclized with hexamethylditin under palladium catalysis conditions followed by a selection of additives for an activated transmetalation. Reactivity and diastereoselectivity for the cyclization strongly depend on the characteristics of additives. A highly diastereoselective synthesis of five-membered rings is achieved from the reaction of the corresponding allenyl (5)-N-tert-butylsulfinimies through the following sequence. After the distannylation of the allenyl group with hexamethylditin catalyzed by the Pd complex, stereochemical routes are additive dependent: addition of SnCl4 affords a cis ring exclusively, whereas a trans ring is formed predominantly by the introduction of B-bromocatecholborane. Extension of the methodology to the synthesis of six-membered cis rings is achieved by using B-bromocatecholborane. Stereochemical relationships of products were unambiguously deduced by X-ray crystallography.
Stereoselective Nickel-Catalyzed [2+2+2] Cycloadditions and Alkenylative Cyclizations of Ene-Allenes and Alkenes
作者:Njamkou N. Noucti、Erik J. Alexanian
DOI:10.1002/anie.201303211
日期:2013.8.5
[2+2+2]=4 (stereocenters)? Nickel‐catalyzed multicomponent cycloadditions and alkenylativecyclizations involving two alkenes and one allene are described. The [2+2+2] cycloaddition provides rapid access to stereochemically complex, cis‐fused hydrindanes. By exchanging P(o‐tol)3 for PBu3 as ligand, the reaction pathway can be diverted to an alkenylativecyclization process.
Pd(0)-Catalyzed Tandem Deprotection/Cyclization of Tetrahydro-β-carbolines on Allenes: Application to the Synthesis of Indolo[2,3-<i>a</i>]quinolizidines
作者:Valerian Gobé、Xavier Guinchard
DOI:10.1021/ol500448j
日期:2014.4.4
The pallado-catalyzed tandemdeprotection/cyclization reaction of enantioenriched N-allyl tetrahydro-β-carbolines on allenes is described. The first step generates in situ a deprotected tetrahydro-β-carboline, which then undergoes a cyclization on the allene function via an intermediate π-allyl Pd(II) derivative. This reaction results in the synthesis of various chiralindolic tetracycles (mainly indolo[2
Key Factors for High Diastereo- and Enantioselectivity of Umpolung Cyclizations of Aldehyde-Containing Allylpalladium Intermediates
作者:Hirokazu Tsukamoto、Ayumu Kawase、Hirotaka Omura、Takayuki Doi
DOI:10.1246/bcsj.20190167
日期:2019.10.15
Two palladium/chiral diphosphine-catalyzed umpolung cyclizations of aldehyde-containing allylic acetates and allenes with arylboronic acid are fully investigated to establish key factors in their h...
A Pd(OAc)(2)-SEGPHOS combination catalyzes the first enantioselective arylative cyclization of allenyl aldehydes with arylboronic acids to provide cis-fused five- and six-membered cyclic homoallylic alcohols. The excellent diastereo- and enantioselectivity and the fact that the reaction proceeds at room temperature in the absence of any additives make the process highly practical.
Stereoselective Synthesis of Chiral Polycyclic Indolic Architectures through Pd<sup>0</sup>-Catalyzed Tandem Deprotection/Cyclization of Tetrahydro-β-carbolines on Allenes
作者:Valérian Gobé、Xavier Guinchard
DOI:10.1002/chem.201500273
日期:2015.6.1
Enantioenriched N‐allyl tetrahydro‐β‐carbolines were prepared by chiral phosphoric acid‐catalyzed Pictet–Spengler reactions. The compounds undergo Pd0‐catalyzed cyclizationsthrough a tandemdeprotection/cyclization process. The regioselectivity of the attack is controlled by the chain length and by the substitution pattern of the allene function. Products resulting from 5‐exo‐ or 6‐exo‐attack were obtained
通过手性磷酸催化的Pictet-Spengler反应制备了对映体富集的N-烯丙基四氢-β-咔啉。这些化合物通过串联的脱保护/环化过程经历Pd 0催化的环化。攻击的区域选择性由链长和丙二烯官能团的取代模式控制。从5 exo-或6 exo-攻击获得的产物的非对映异构体比例高达95:5。Azepinopyrrido [3,4 b ]吲哚通过7-获得内切-cyclizations。