100420-10-8Relevant articles and documents
Synthesis of secondary and tertiary amides without coupling agents from amines and potassium acyltrifluoroborates (KATs)
Bode, Jeffrey W.,Ryan, Sarah J.,Schuhmacher, Anne,Shiro, Tomoya
, p. 7609 - 7614 (2020)
Although highly effective for most amide syntheses, the activation of carboxylic acids requires the use of problematic coupling reagents and is often poorly suited for challenging cases such as N-methyl amino acids. As an alternative to both secondary and tertiary amides, we report their convenient synthesis by the rapid oxidation of trifluoroborate iminiums (TIMs). TIMs are easily prepared by acid-promoted condensation of potassium acyltrifluoroborates (KATs) and amines and are cleanly and rapidly oxidized to amides with hydrogen peroxide. The overall transformation can be conducted either as a one-pot procedure or via isolation of the TIM. The unique nature of the neutral, zwitterionic TIMs makes possible the preparation of tertiary amides via an iminium species that would not be accessible from other carbonyl derivatives and can be conducted in the presence of unprotected functional groups including acids, alcohols and thioethers. In preliminary studies, this approach was applied to the late-stage modifications of long peptides and the iterative synthesis of short, N-methylated peptides without the need for coupling agents.
Unified Approach to the Chemoselective α-Functionalization of Amides with Heteroatom Nucleophiles
Gon?alves, Carlos R.,Lemmerer, Miran,Teskey, Christopher J.,Adler, Pauline,Kaiser, Daniel,Maryasin, Boris,González, Leticia,Maulide, Nuno
, p. 18437 - 18443 (2019)
Functionalization at the α-position of carbonyl compounds has classically relied on enolate chemistry. As a result, the generation of a new C-X bond, where X is more electronegative than carbon requires an oxidation event. Herein we show that, by rendering the α-position of amides electrophilic through a mild and chemoselective umpolung transformation, a broad range of widely available oxygen, nitrogen, sulfur, and halogen nucleophiles can be used to generate α-functionalized amides. More than 60 examples are presented to establish the generality of this process, and calculations of the mechanistic aspects underline a fragmentation pathway that accounts for the broadness of this methodology.
Chemoselective α,β-Dehydrogenation of Saturated Amides
Teskey, Christopher J.,Adler, Pauline,Gon?alves, Carlos R.,Maulide, Nuno
supporting information, p. 447 - 451 (2019/01/04)
We report a method for the selective α,β-dehydrogenation of amides in the presence of other carbonyl moieties under mild conditions. Our strategy relies on electrophilic activation coupled to in situ selective selenium-mediated dehydrogenation. The α,β-unsaturated products were obtained in moderate to excellent yields, and their synthetic versatility was demonstrated by a range of transformations. Mechanistic experiments suggest formation of an electrophilic SeIV species.
Flexible and Chemoselective Oxidation of Amides to α-Keto Amides and α-Hydroxy Amides
De La Torre, Aurélien,Kaiser, Daniel,Maulide, Nuno
supporting information, p. 6578 - 6581 (2017/05/29)
A suite of flexible and chemoselective methods for the transition-metal-free oxidation of amides to α-keto amides and α-hydroxy amides is presented. These highly valuable motifs are accessed in good to excellent yields and stereoselectivities with high functional group tolerance. The utility of the method is showcased by the formal synthesis of a potent histone deacetylase inhibitor.
Chemoselective Intermolecular Cross-Enolate-Type Coupling of Amides
Kaiser, Daniel,Teskey, Christopher J.,Adler, Pauline,Maulide, Nuno
supporting information, p. 16040 - 16043 (2017/11/22)
A new approach for the synthesis of 1,4-dicarbonyl compounds is reported. Chemoselective activation of amide carbonyl functionality and subsequent umpolung via N-oxide addition generates an electrophilic enolonium species that can be coupled with a wide range of nucleophilic enolates. The method conveys broad functional group tolerance on both components, does not suffer from formation of homocoupling byproducts and avoids the use of transition metal catalysts.
Visible light photoredox-catalyzed deoxygenation of alcohols
Rackl, Daniel,Kais, Viktor,Kreitmeier, Peter,Reiser, Oliver
, p. 2157 - 2165 (2015/01/09)
Carbon-oxygen single bonds are ubiquitous in natural products whereas efficient methods for their reductive defunctionalization are rare. In this work an environmentally benign protocol for the activation of carbon-oxygen single bonds of alcohols towards a reductive bond cleavage under visible light photocatalysis was developed. Alcohols were activated as 3,5-bis(trifluoromethyl)-substituted benzoates and irradiation with blue light in the presence of [Ir(ppy)2( dtb-bpy)](PF6 ) as visible light photocatalyst and Hünig's base as sacrificial electron donor in an acetonitrile/water mixture generally gave good to excellent yields of the desired defunctionalized compounds. Functional group tolerance is high but the protocol developed is limited to benzylic, α-carbonyl, and α-cyanoalcohols; with other alcohols a slow partial C-F bond reduction in the 3,5-bis(trifluoromethyl)benzoate moiety occurs.
Chemoselective intermolecular α-arylation of amides
Peng, Bo,Geerdink, Danny,Fares, Christophe,Maulide, Nuno
supporting information, p. 5462 - 5466 (2014/06/09)
A new approach for the fully chemoselective α-arylation of amides is presented. By means of electrophilic amide activation, aryl groups can be regioselectively introduced α- to amides, even in the presence of esters and alkyl ketones. Mechanistic studies reveal key reaction intermediates and emphasize a remarkably subtle base effect in this transformation. Arylating me softly: A new approach for the fully chemoselective α-arylation of amides has been developed. When electrophilic amide activation is employed, aryl groups can be regioselectively introduced in the position α to the amide, and that even in the presence of esters or alkyl ketones. Mechanistic studies emphasize a remarkably subtle base effect in this transformation.
