34636-09-4Relevant articles and documents
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Ashby,E.C.,Noding,S.R.
, p. 117 - 128 (1979)
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Desymmetric enantioselective reduction of cyclic 1,3-diketones catalyzed by a recyclable p-chiral phosphinamide organocatalyst
Qin, Xu-Long,Li, Ang,Han, Fu-She
supporting information, p. 2994 - 3002 (2021/03/01)
The P-stereogenic phosphinamides are a structurally novel skeletal class which has not been investigated as chiral organocatalysts. However, chiral cyclic 3-hydroxy ketones are widely used as building blocks in the synthesis of natural products and bioactive compounds. However, general and practical methods for the synthesis of such chiral compounds remain underdeveloped. Herein, we demonstrate that the P-stereogenic phosphinamides are powerful organocatalysts for the desymmetric enantioselective reduction of cyclic 1,3-diketones, providing a useful method for the synthesis of chiral cyclic 3-hydroxy ketones. The protocol displays a broad substrate scope that is amenable to a series of cyclic 2,2-disubstituted five- and six-membered 1,3-diketones. The chiral cyclic 3-hydroxy ketone products bearing an all-carbon chiral quaternary center could be obtained with high enantioselectivities (up to 98% ee) and diastereoselectivities (up to 99:1 dr). Most importantly, the reactions could be practically performed on the gram scale and the catalysts could be reused without compromising the catalytic efficiency. Mechanistic studies revealed that an intermediate formed from P-stereogenic phosphinamide and catecholborane is the real catalytically active species. The results disclosed herein bode well for designing and developing other reactions using P-stereogenic phosphinamides as new organocatalysts.
Cine-Silylative Ring-Opening of α-Methyl Azacycles Enabled by the Silylium-Induced C-N Bond Cleavage
Zhang, Jianbo,Chang, Sukbok
supporting information, p. 12585 - 12590 (2020/08/21)
Described herein is the development of a borane-catalyzed cine-silylative ring-opening of α-methyl azacycles. This transformation involves four-step cascade processes: (i) exo-dehydrogenation of alicyclic amine, (ii) hydrosilylation of the resultant enamine, (iii) silylium-induced cis-β-amino elimination to open the ring skeleton, and (iv) hydrosilylation of the terminal olefin. The present borane catalysis also works efficiently for the C-N bond cleavage of acyclic tertiary amines. On the basis of experimental and computational studies, the silicon atom was elucidated to play a pivotal role in the β-amino elimination step.
Direct Reductive Amination of Carbonyl Compounds Catalyzed by a Moisture Tolerant Tin(IV) Lewis Acid
Sapsford, Joshua S.,Scott, Daniel J.,Allcock, Nathan J.,Fuchter, Matthew J.,Tighe, Christopher J.,Ashley, Andrew E.
supporting information, p. 1066 - 1071 (2018/01/27)
Despite the ever-broadening applications of main-group ‘frustrated Lewis pair’ (FLP) chemistry to both new and established reactions, their typical intolerance of water, especially at elevated temperatures (>100 °C), represents a key barrier to their mainstream adoption. Herein we report that FLPs based on the Lewis acid iPr3SnOTf are moisture tolerant in the presence of moderately strong nitrogenous bases, even under high temperature regimes, allowing them to operate as simple and effective catalysts for the reductive amination of organic carbonyls, including for challenging bulky amine and carbonyl substrate partners. (Figure presented.).