Cationic chiral Au(I) complexes catalyze asymmetric Pictet-Spenglerreactions between tryptamines and arylaldehydes. The resulting tetrahydro-β-carbolines are obtained with wide functional group tolerance in high yield and with high enantioselectivities (up to 95%). Aldehydes bearing polar or protic functions are well tolerated. The reaction features a hitherto unknown C2-auration of the indole as
Syntheses of Strychnine, Norfluorocurarine, Dehydrodesacetylretuline, and Valparicine Enabled by Intramolecular Cycloadditions of Zincke Aldehydes
作者:David B. C. Martin、Lucas Q. Nguyen、Christopher D. Vanderwal
DOI:10.1021/jo2020246
日期:2012.1.6
base-mediated intramolecular Diels–Alder cycloadditions of tryptamine-derived Zincke aldehydes is described. This important complexity-generating transformation provides the tetracyclic core of many indole monoterpene alkaloids in only three steps from commercially available starting materials and played a key role in short syntheses of norfluorocurarine (five steps), dehydrodesacetylretuline (six steps), valparicine
N-Propargyl tryptamines bearing N-substituents such as propargyl, allyl, alkyl or benzyl groups undergo regioselective gold-catalyzed cyclizations to the corresponding spiroindolenines, while it was previously shown that N-sulfonyl-N-propargyl tryptamines lead to achiral azepino[4,5-b]indoles. An asymmetric approach to these spiroindolenines is disclosed using chiral gold complexes, leading to enantiomeric
Ñ -Propargyl色胺轴承ñ -取代基如炔丙基,烯丙基,烷基或苄基团经历区域选择性金催化的环化反应,以相应的spiroindolenines,而先前被显示Ñ -sulfonyl- Ñ -propargyl色胺导致的非手性氮杂并[4, 5- b ]吲哚。使用手性金络合物公开了对这些螺环吲哚胺的不对称方法,导致对映体比率高达84/16。可以使用惠斯根环化,钯催化的交叉偶联或还原将螺环吲哚啉后期官能化。计算研究表明,取决于胺上取代基的性质,反应是通过不同的机理途径进行的。
Synthesis of novel chiral guanidine catalyst and its application in the asymmetric Pictet-Spengler reaction
作者:Saeed Ahmad、Lakshmi Shukla、Joanna Szawkało、Piotr Roszkowski、Jan K. Maurin、Zbigniew Czarnocki
DOI:10.1016/j.catcom.2016.10.008
日期:2017.1
A new chiral guanidine catalyst has been synthesized by the reaction of (R)-1-(1-phenylethyl)guanidine and 2,3-diphenylcycloprop-2-enone. The catalyst was evaluated for the Pictet-Spenglerreaction in which tetrahydro-β-carbolines were obtained in good yields with up to 64% ee.
Metal‐Free Dearomatization: Direct Access to Spiroindol(en)ines in Batch and Continuous‐Flow
作者:Prabhat Ranjan、Gerardo M. Ojeda、Upendra K. Sharma、Erik V. Van der Eycken
DOI:10.1002/chem.201805945
日期:2019.2.18
A metal‐free, phosphine‐catalyzed intramolecular “umpolung Michael addition” on alkynes to form spiroindol(en)ines is reported. This nucleophilic catalysis enables the formation of a wide scope of five‐ and six‐membered spiroindol(en)ines in moderate to excellent yields in batch as well as under continuous‐flow conditions. Triphenylphosphine‐catalyzed nucleophilic activation of alkynes allows the exclusive