899419-79-5Relevant academic research and scientific papers
Palladium-Catalyzed Oxidation-Hydroxylation and Oxidation-Methoxylation of N -Boc Indoles for the Synthesis of 3-Oxoindolines
Zhou, Xiao-Yu,Chen, Xia,Wang, Liang-Guang,Yang, Dan,Li, Zhi
, p. 3662 - 3669 (2017/08/15)
The palladium-catalyzed oxidation-hydroxylation and oxidation-methoxylation of N -Boc indoles for the synthesis of tert -butyl 2-hydroxy(methoxy)-3-oxoindoline-1-carboxylates and their derivatives is developed. The process occurs readily using PdCl 2 as the catalyst and acetonitrile as the solvent to afford 3-oxoindolines in moderate to high yields. A mechanism for this Pd-catalyzed oxidation-hydroxylation and oxidation-methoxylation of N -Boc indoles is proposed.
Combining Zn ion catalysis with homogeneous gold catalysis: An efficient annulation approach to N-protected indoles
Wang, Yanzhao,Liu, Lianzhu,Zhang, Liming
, p. 739 - 746 (2013/03/13)
The Fischer indole synthesis is perhaps the most powerful method for indole preparation, but it often suffers from low regioselectivities with unsymmetrical aliphatic ketone substrates and strongly acidic conditions and is not suitable for α,β-unsaturated ketones. In this edge article, we disclose an efficient synthesis of N-protected indoles from N-arylhydroxamic acids/N-aryl-N-hydroxycarbamates and a variety of alkynes via cooperative gold and zinc catalysis. The zinc catalysis is similar to the related zinc ion catalysis in metalloenzymes such as human carbonic anhydrase II and substantially enhances the O-nucleophilicity of N-acylated hydroxylamine by forming the corresponding Zn chelates. The Zn chelates can attack gold-activated alkynes to form O-alkenyl-N-arylhydroxamates, which can undergo facile 3,3-sigmatropic rearrangements and subsequent cyclodehydrations to yield N-protected indole products. This new chemistry offers several important improvements over the Fischer indole synthesis: (a) the reaction conditions are mildly acidic and can tolerate sensitive groups such as Boc; (b) broader substrate scopes including substrates with pendant carbonyl groups (reactive in the Fischer chemistry) and alkyl chlorides; (c) better regioselectivities for the formation of 2-substituted indoles under much milder conditions; (d) 2-alkenylindoles can be prepared readily in good to excellent yields, for which Fischer chemistry could not be used; (e) with internal alkynes both steric and electronic controls are available for achieving good regioselectivities, while Fischer chemistry is in general problematic. The Royal Society of Chemistry 2013.
Ruthenium-catalyzed asymmetric hydrogenation of N-Boc-indoles
Kuwano, Ryoichi,Kashiwabara, Manabu
, p. 2653 - 2655 (2007/10/03)
Highly enantioselective hydrogenation of various N-Boc-indoles proceeded successfully in the presence of the ruthenium complex generated from an appropriate ruthenium precursor and a trans-chelate chiral bisphosphine PhTRAP. Various 2- or 3-substituted indoles were converted into chiral indolines with high enantiomeric excesses (up to 95% ee). The PhTRAP-ruthenium catalyst was able to promote the hydrogenation of 2,3-dimethylindoles, giving cis-2,3-dimethylindolines with 72% ee.
