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.