Gold-Catalyzed Oxidative Arylations of 3-Butyn-1-ols and 2-Propyn-1-ols with Nitrones to Yield Distinct Fused Indoles Bearing a Heterocyclic Ring
作者:Rajkumar Lalji Sahani、Rai-Shung Liu
DOI:10.1021/acscatal.9b01491
日期:2019.7.5
The catalytic formation of various fused indoles from the nitrone oxidations of 1-substituted n-yn-1-ols (n = 2, 3) is described. For 3-butyn-1-ols, the oxidations yield tetrahydropyrano[4,3-b]indoles, whereas 2-propynols deliver tetrahydro-[1,2]oxazino[5,4-b]indoles efficiently. When styryl nitrones were tested on 2-propyn-1-ols, dihydrooxazolo[3,4-a]indoles were produced efficiently. We postulate
描述了由1-取代的n -yn-1-ols(n = 2,3)的硝酮氧化催化形成各种稠合吲哚的方法。对于3-丁炔-1-醇,氧化产生四氢吡喃并[4,3- b ]吲哚,而2-丙炔醇有效地递送四氢-[1,2]恶嗪基[5,4- b ]吲哚。当在2-丙炔-1-醇上测试苯乙烯基硝酮时,可以高效地生产二氢恶唑并[3,4- a ]吲哚。我们假定这些稠合的吲哚的形成是由共同的机理引起的,该机制涉及在这些稠合的吲哚之前,初始的烯基金中间体的[3,3]-σ位移以提供羰基化作用。
Synthesis of novel spiro-isoxazoline and spiro-isoxazolidine derivatives of tomentosin
A series of novel enantiomerically pure spiro-isoxazolidines and spiro-isoxazolines were synthesized regioselectively by 1,3-dipolarcycloadditionusing respectively two dipoles, nitrones and nitrileoxides, on the exocyclic double bond of the B ring of tomentosin (α-methylene-γ-butyrolactone), a sesquiterpene lactone extracted from Dittrichia viscosa.
Catalytic Transformations of Alkynes into either α-Alkoxy or α-Aryl Enolates: Mannich Reactions by Cooperative Catalysis and Evidence for Nucleophile-Directed Chemoselectivity
作者:Rajkumar Lalji Sahani、Manoj D. Patil、Sachin Bhausaheb Wagh、Rai-Shung Liu
DOI:10.1002/anie.201806883
日期:2018.11.5
The catalytic formation of gold enolatesfrom alkynes, nitrones, and nucleophiles is described, and their Mannich reactions result in nucleophile‐directed chemoselectivity through cooperative catalysis. For 1‐alkyn‐4‐ols and 2‐ethynylphenols, their gold‐catalyzed nitrone oxidations afforded N‐containing dihydrofuran‐3(2H)‐ones with syn selectivity. The mechanism involves the Mannich reactions of gold
Gold-Catalyzed Cyclization-Cycloaddition Cascade Reactions of Allenyl Acetals with Nitrones
作者:Dhananjayan Vasu、Rai-Shung Liu
DOI:10.1002/chem.201201777
日期:2012.10.22
Gold and silver: When allenyl acetals and nitrones are treated with a catalytic amount of a gold complex and a silver salt they react through a cyclization—cycloaddition cascadereaction to give a mixture of diastereomeric tricyclic products. The mixture converges to a single product upon acid hydrolysis (see scheme). The key intermediate is postulated to be a 1‐methoxyfulvene species.
An efficient, copper-catalyzed [3+1+1] cycloaddition reaction was developed for the expedient synthesis of pharmacologically interesting polysubstituted pyrroles from easily available nitrones and α-acidic isocyanides. The given approach features a new mode of cycloaddition between nitrones and isocyanides with wide substrate scope, good functional group tolerance, and operational simplicity. The operando